A Probiotic Containing L. Plantarum and P. Acidilactici Strains for Treating Upper Respiratory Infection in Children Aged 6 Months to 5 Years: A Randomized, Double-Blind Trial

A Probiotic Containing L. Plantarum and P. Acidilactici Strains for Treating Upper Respiratory Infection in Children Aged 6 Months to 5 Years: A Randomized, Double-Blind Trial | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article A Probiotic Containing L. Plantarum and P. Acidilactici Strains for Treating Upper Respiratory Infection in Children Aged 6 Months to 5 Years: A Randomized, Double-Blind Trial Diana M. Andrade-Platas, Marta Gloria Martinez-Figueroa, Maria Rodriguez-Palmero, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7214019/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 26 Nov, 2025 Read the published version in European Journal of Pediatrics → Version 1 posted 9 You are reading this latest preprint version Abstract Upper respiratory infections (URIs) are highly prevalent, especially among young children. We aimed to investigate the efficacy and safety of a specific probiotic formula in shortening the duration of pediatric URIs of viral origin. A randomized, double-blind clinical trial was conducted in children aged 6 months to 5 years, with URI with pharyngitis as diagnosed by a specialist. Participants were allocated to probiotic (strains L. plantarum KABP022, KABP023 and KABP033, and P. acidilactici KABP021) or placebo, twice daily for 15 days, and further followed up at 30 and 60 days from baseline. Antipyretic (ibuprofen) and antihistamine (cetirizine) were allowed as comedication and controlled. Co-primary outcomes were days of fever (axillary temperature >37.5ºC) and days of pain/discomfort (Face, Legs, Activity, Cry and Consolability [FLACC] score >3), as recorded in a diary. Causative viruses were identified by PCR in nasopharyngeal swabs. 75 children were randomized and included in the analysis. Most frequent causative agents were rhinoviruses, coronaviruses and respiratory syncytial virus. Compared to placebo, duration of fever and of pain/discomfort were reduced by 1.1 days (95%CI 0.5-1.7; p=0.001), and by 0.7 days (95%CI 0.2-1.2; p=0.006) in probiotic group, respectively. Sensitivity analyses by detected virus, age, sex and recent URI episodes produced similar results. Use of comedication and other symptoms did not differ between study groups. No significant differences were found in the number of adverse events between the groups. Conclusion: Intervention with this probiotic formula was associated with shorter duration of fever and pain/discomfort in pediatric URIs with pharyngitis. Trial Registration: Prospectively registered on Oct 5 th , 2023, as ISRCTN-66122782. Upper respiratory infection virus probiotic Lactiplantibacillus plantarum Pediococcus acidilactici Figures Figure 1 Figure 2 What is known Acute upper respiratory tract infections (URIs) are highly prevalent in children, but due to their frequent viral etiology, treatment is often symptomatic only. Some probiotics have shown promising results against URIs, but evidence mostly relies on untrained, subjective diagnosis by participants or their parents. Recently, a probiotic formula containing strains L. plantarum KABP022, KABP023 and KABP033, and P. acidilactici KABP021 reduced viral load and duration of symptoms in a randomized trial in 300 adults with laboratory-confirmed Covid19, against placebo. What is New: In children with URI with pharyngitis, as diagnosed by a specialist, intervention with said probiotic formula reduced the duration both of fever and of pain/discomfort, compared to placebo. Results were robust to sensitivity analyses by age, sex, number of recent URIs and by most prevalent causative viruses in the study population. Introduction Acute upper respiratory tract infections (URIs) are highly prevalent, especially in children [ 1 ]. Clinical symptoms are usually self-limited, but occasionally the infection spreads to adjacent organs, yielding more serious clinical manifestations [ 2 ]. URIs reduce quality of life for the affected children and their parents, and result in medical and non-medical costs. Causative agents in children are mainly viruses, the most prevalent since the onset of the Covid19 pandemic being rhinoviruses, respiratory syncytial virus (RSV) and SARS-CoV2 [ 3 , 4 ]. Lack of antiviral therapies against most URI viruses usually limits treatment to symptom management ( e.g. antipyretics, antihistamines). Probiotics are defined as “live microorganisms that when administered in adequate amounts, confer a health benefit on the host” [ 5 ]. Mounting evidence indicates a crosstalk between the gastro-intestinal tract and the respiratory system, along with their respective microbiomes, referred to as the gut-lung axis [ 6 , 7 ]. In this regard, recent meta-analyses found oral probiotics may help prevent or shorten upper respiratory infections such as cold and influenza, but also noted significant limitations, such as high heterogeneity, overreliance on subjective diagnosis and unclear treatment concealment [ 8 , 9 ]. Of note, heterogeneity is not unexpected, as probiotic immune effects are considered to be strain-specific [ 5 , 10 – 12 ]. The AB21® probiotic formula includes four strains of the Lactobacillaceae family: Lactiplantibacillus plantarum KABP022, KABP023 and KABP033, plus Pediococcus acidilactici KABP021. A previous randomized clinical trial in 300 adult patients found this formula improved PCR-confirmed Covid19, according both to objective signs ( e.g. viral load, digital chest X-ray) and subjective symptoms [ 13 ]. However, evidence of its effect against other viruses and in the pediatric population was lacking. In this study, we aimed to test the efficacy and safety of the same probiotic formula in shortening the duration of specialist-diagnosed URIs of viral origin, in a pediatric population. Methods Study design and setting We conducted a randomized, single-center, double-blind, placebo-controlled trial with two parallel arms. The study was conducted at Hospital Medica Sur (Mexico City, Mexico). Approval was duly obtained from the hospital’s Committee for Ethics and Research in Studies in Humans (approval ref. CB148-CEI153). The study adhered to the tenets of the Declaration of Helsinki, was prospectively registered as ISRCTN-66122782 and is reported according to Consolidated Standards of Reporting Trials (CONSORT). Participants We included pediatric participants, aged 6 months to 5 years, with an upper respiratory infection with fever and pharyngitis, as diagnosed by a pediatrician, and symptoms’ onset within 48h of enrolment. Parents had to report the child experiencing fever (> 37.5ºC) and a FLACC score (Face, Legs, Activity, Crying and Consolability) > 3 [ 14 ], and to provide written informed consent. Exclusion criteria were: i) Symptoms suggestive of bacterial infection (tonsillitis or tonsillar exudate, cervical lymphadenitis, otitis media or scarlatiniform rash); ii) preterm infants or those weighting 48h within 2 weeks of study entry (applied to infants and mothers of breastfed participants); v) history of ≥ 2 invasive infections (meningitis, osteomyelitis, sepsis); vi) history of recurrent, severe respiratory infections (upper or lower) within 12 months of study entry; vii) chronic diarrhea or gastroesophageal reflux disease; viii) congenital heart, respiratory or digestive disease; ix) primary or secondary immunodeficiency; and, x) asthma. Procedures The study consisted of a 15-day intervention phase (Visits 1 to 2) plus a 45-day follow-up phase (Visits 3 and 4, Supplementary Fig. 1). A computer-generated 1:1 (probiotic:placebo) randomization list, of block size 4, was prepared by personnel not directly participating in the study and kept in a sealed envelope until study completion. Study investigators recruited and allocated patients and performed all study procedures. Investigators, parents and pediatric participants were blinded to treatment allocation. Probiotic and placebo capsules looked identical, both contained an off-white powder, and both were delivered in undistinguishable, anonymous boxes. At Visit 1 (baseline, day 0), parents of eligible participants who provided informed consent received the allocated intervention and were briefed both on product administration and use of the patient diary for daily recording of: i) symptoms (axillary temperature (ºC), FLACC score, and presence/absence of each of cough, rhinorrhea and nasal congestion); ii) comedication; and iii) adverse events (AEs). A nasopharyngeal swab (Copan, Italy) was taken and stored at -20ºC in Universal Transport Medium for posterior analysis of causative agents. At Visit 2 (day 15 from enrolment), patient diaries were returned, investigators verified study compliance and assessed clinical status of participants and unsolicited AEs. Clinical status of participants and unsolicited AEs were assessed again during follow-up at Visits 3 and 4 (30 and 60 days from enrolment ± 3 days, respectively). Analysis of causative agents was performed in batch at Grupo Diagnostico Aries (Mexico), using the Respiratory Flow multiplex PCR (Vitro SA, Spain). Interventions All treatments were taken orally. Probiotic or equally looking placebo were taken twice daily (morning and evening). Probiotic capsules contained lyophilized Pediococcus acidilactici strain KABP021 (CECT7483) and Lactiplantibacillus plantarum strains KABP022 (CECT7484), KABP023 (CECT7485) and KABP033 (CECT30292), totaling ≥ 2 billion CFUs (colony-forming units, as per plate counting in MRS medium), in a dextrin carrier. Placebo capsules contained the dextrin carrier only. Microbial quality was verified as described elsewhere [ 13 ]. Parents were instructed to open the capsules and dissolve the content in water or lukewarm milk, right before administration. Study participants could also receive standard of care for pediatric URIs, consisting of ibuprofen as antipyretic drug (10 mg/Kg of body weight per day) and/or cetirizine as antihistamine drug (0.25 mg/Kg of body weight per day) as rescue medication. Should study participants develop symptoms of bacterial infection after study entry, investigators could prescribe rescue antibiotics: amoxicillin clavulanate (at 45mg/Kg of body weight per day), or clarithromycin (at 7.5 mg/Kg of body weight per day) in case of allergy to beta-lactams. No antivirals were used during the study. Predefined outcomes The co-primary study outcomes were the number of days with fever ( i.e. highest daily axillary temperature > 37.5ºC) and the number of days with pain/discomfort score > 3 (as measured with the FLACC score)[ 14 ] during the intervention period. Secondary outcomes included: i) Area Under the Curve (AUC) of body temperature and FLACC score during the intervention period; ii) number of days with cough, nasal congestion, rhinorrhea, use of antipyretic (ibuprofen), use of antihistamine (cetirizine) and use of antibiotics, during the intervention period; iii) number of unscheduled medical visits during the intervention period as reported by parents at Visit 2; iv) occurrence of each of the different symptoms (axillary temperature > 37.5ºC, FLACC > 3, cough, rhinorrhea and nasal congestion) and their total number, as assessed by investigators at Visits 3 and 4; v) number of unscheduled medical visits as reported by parents at Visits 3 and 4. Because participants attended Visit 2 (day 15) at different times of the day (morning, afternoon or evening), only data from finished days ( i.e. 1 to 14) was used in outcomes related to the intervention period to ensure comparability between participants. Power calculation and statistical analysis Sample size was calculated to allow detecting a difference in duration of 1 day with a standard deviation (SD) of 1.2 days, a statistical power of 90% and alpha of 2.5% ( i.e. multiplicity-adjusted for two co-primary endpoints), leading to 36 participants per group. This number was increased to 45 per group to allow for a drop-out rate of 20%. Statistical analysis was performed on all randomized patients (intent-to-treat) by allocated group, using IBM SPSS Statistics program (version 22). Differences in baseline characteristics between groups were not formally assessed using p-values, following CONSORT 2010 and European Medicines Agency (EMA) guidelines. Differences between study groups for the co-primary endpoints (days of highest axillary temperature > 37.5ºC and of FLACC score > 3) were assessed with generalized linear models (GLM), with baseline temperature or FLACC score as covariates (respectively); normality of residuals was verified by Q-Q plots. Differences between groups for secondary endpoints were assessed by Mann-Whitney test (exact version) for continuous or ordinal data, and Chi-Squared test (with N-1 correction)[ 15 ] for categorical data. In exploratory analyses, GLMs for the co-primary endpoints were adjusted for detection rhinovirus (yes/no), detection of coronaviruses (yes/no), detection of RSV (yes/no), age (up to 12 months vs . older), sex (male/female) and number of URIs in the previous two months. Spearman test was used to assess bivariate correlations. All tests were two-sided. Results Participants From October 2022 to February 2023, 75 pediatric participants were recruited, underwent the 15-day intervention and were followed-up until the last study visit, 2 months from randomization (Fig. 1 ). As no dropouts were observed, recruitment was stopped before reaching 90 participants once target statistical power was achieved for the co-primary outcomes. Median age was 15 months and 39 (52.0%) were female. Other than fever (> 37.5ºC) and a FLACC score > 3 as per entry criteria, the most common URI symptom was rhinorrhea (82.7%), and most participants were already taking ibuprofen (93.3%). Baseline characteristics were well-balanced between study groups (Table 1 ). Table 1 Baseline characteristics of study participants. Placebo (n = 38) Probiotic (n = 37) Age (months; median, range) 14.5 (6–59) 15.0 (6–53) Weight at birth (Kg; mean, SD) 3.16 (0.25) 3.23 (0.31) Sex (female; N, %) 16 (42,1%) 20 (54,1%) Born by C-section (N, %) 16 (43.2%) 14 (37.5%) Breastfed until 6 months of age (N, %) 32 (84.2%) 32 (86.5%) Completed scheduled vaccines by age (N, %) 38 (100%) 37 (100%) Current weight (Kg; median, range) 10.1 (6.8–24.2) 10.1 (6.5–22.1) Currently attending kindergarten (N, %) 32 (84.2%) 29 (78.4%) Number of URIs within two months (mean, SD) 1.5 (1.0) 1.8 (0.8) Body temperature at baseline (ºC; mean, SD) 37.8 (0.7) 37.7 (0.8) FLACC score at baseline (median, range) 8.0 (4–9) 7.0 (4–9) Presence of other URI symptoms baseline: • Rhinorrhea (N, %) • Nasal congestion (N, %) • Cough (N, %) 33 (86.8%) 22 (57.9%) 22 (57.9%) 29 (78.4%) 20 (54.1%) 22 (59.5%) Using antipyretics at baseline (N, %) 35 (92.1%) 35 (94.6%) Using antihistamines at baseline (N, %) 12 (31.6%) 10 (27.0%) Hours since the onset of symptoms (mean, SD) 21.8 (11.8) 22.2 (12.0) Oxygen saturation at baseline (SpO 2 ; mean, SD) 95.4 (1.9) 95.0 (1.8) Number of viruses detected (mean, SD) 1.4 (1.0) 1.3 (0.8) All patients provided nasopharyngeal swabs. Most frequent etiologic agents were rhinoviruses (36.0%), coronaviruses (28.0%, mostly SARS-CoV2) and respiratory syncytial virus (RSV, 25.3%). Several patients were positive for more than one virus. Overall distribution of viruses did not differ between study groups ( Supplementary Fig. 1 ). Primary Outcomes There were 1.1 less days of fever (95%CI 0.5 to 1.7; p = 0.001) and 0.7 days less of pain/discomfort (95%CI 0.2 to 1.2; p = 0.006) in the probiotic group, compared to placebo (Fig. 2 ). Higher temperature and FLACC score at study entry resulted in more days of fever and of pain/discomfort, respectively ( i.e. baseline effect, both p < 0.001). Secondary Outcomes During the intervention phase, AUC for body temperature and FLACC score were significantly lower in probiotic group vs. placebo (both p < 0.05), but no differences were found in the duration of other symptoms (rhinorrhea, nasal congestion and cough). Likewise, days of use of antipyretic and of antihistamine did not differ between study groups. During the six-week follow-up phase, incidence of nasal congestion and total number of symptoms were significantly lower in probiotic group at Visit 3 compared to placebo ( i.e. 15 days after completing the intervention, p < 0.05), but not at Visit 4. Noteworthy, all participants displaying symptoms at Visit 3 had already achieved axillary temperature < 37.5ºC and a FLACC score of 0 at Visit 2. The complete list of secondary endpoints is reported on Table 2 . Table 2 Secondary outcomes. Median (range) or number of participants (% within group). Placebo (n = 38) Probiotic (n = 37) P-value Intervention phase (reported at Visit 2) a AUC temperature (ºC) 517 (505–525) 515 (505–522) 0.021 AUC FLACC score 39.5 (10.0-53.5) 31.0 (7.0–51.0) 0.002 Days with cough 4 (0–14) 2 (0–13) 0.488 Days with nasal congestion 2.5 (0–12) 1 (0–12) 0.522 Days with rhinorrhea 7 (0–13) 5 (0–13) 0.267 Days of use of antipyretic (ibuprofen) 4 (2–7) 4 (2–6) 0.108 Days of use of antihistamine (cetirizine) 5.5 (0–12) 4 (0–13) 0.630 Participants using antibiotics 1 (2.6%) 0 (0%) 0.324 Participants with emergency medical visits 0 (0%) 0 (0%) 1.000 Follow-up days 16 to 30 (reported at Visit 3) Presence of fever (> 37.5 ºC) 7 (18.4%) 4 (10.8%) 0.355 Presence of pain/discomfort (FLACC > 3) 7 (18.4%) 5 (13.5%) 0.565 Presence of cough 2 (5.3%) 2 (5.4%) 0.978 Presence of nasal congestion 7 (18.4%) 1 (2.7%) 0.029 Presence of rhinorrhea 8 (21.1%) 4 (10.8%) 0.230 Number of symptoms b 4 (2–5) 3 (1–4) 0.019 Participants with emergency medical visits 1 (2.6%) 0 (0%) 0.324 Follow-up days 31 to 60 (reported at Visit 4) Presence of fever (> 37.5 ºC) 8 (21.1%) 9 (24.3%) 0.783 Presence of pain/discomfort (FLACC > 3) 8 (21.1%) 9 (24.3%) 0.737 Presence of cough 10 (26.3%) 5 (13.5%) 0.169 Presence of nasal congestion 7 (18.4%) 9 (24.3%) 0.535 Presence of rhinorrhea 8 (21.1%) 10 (27.0%) 0.547 Number of symptoms c 5 (1–5) 4 (1–5) 0.215 Participants with emergency medical visits 0 (0%) 1 (2.7%) 0.311 a) Data from patient diaries, except for number of emergency medical visits; b) Among symptom-positive participants at Visit 3 (probiotic n = 6, placebo n = 8); c) Among symptom-positive participants at Visit 4 (probiotic n = 13, placebo n = 11). Exploratory Outcomes Post-hoc analyses were conducted to assess the impact of the most frequently detected viruses (rhinovirus, coronaviruses and RSV), age, sex and number of recent URIs (ranging 0 to 3) on co-primary endpoints. Probiotic intervention was still superior to placebo after adjusting for each of these factors, both for fever and for pain/discomfort (p < 0.01, Supplementary Table 1 ). Patients positive for coronaviruses (n = 21) had 0.7 more days of fever on average (p = 0.041). Conversely, patients positive for RSV (n = 19) had 0.8 more days of pain/discomfort on average (p = 0.004). Other variables assessed did not influence the duration of fever or pain. Days of use of antipyretic correlated with days of fever (rho = 0.56, p < 0.001) and of pain/discomfort (rho = 0.71, p < 0.001), while days of use of antihistamine correlated with days of rhinorrhea (rho = 0.85, p < 0.001). Days of fever and of pain/discomfort markedly correlated one another (rho = 0.78, p < 0.001), while days of rhinorrhea and of congestion mildly correlated one another (rho = 0.26, p = 0.022). Bivariate correlations can be found on Supplementary Table 2 . Safety No severe AEs or hospitalizations were reported during the study. All reported AEs were of gastrointestinal type, mild and self-limited, and their numbers did not differ between study groups ( Supplementary Table 3 ). Discussion In this randomized, placebo-controlled study, probiotic intervention was associated with a shorter duration of fever and pain/discomfort, in children with an upper respiratory infection (URI) of likely viral origin with pharyngitis, as diagnosed by a pediatrician. On average, the duration of fever was shortened to 1.6 days vs. 2.7 in the placebo ( i.e. 1.1 less days, a 40% reduction), and pain/discomfort was shortened to 3.7 days vs . 4.4 in the placebo ( i.e. 0.7 less days, a 19% reduction). Results were robust to a variety of sensitivity analyses, including type of virus and participant’s age, sex and recent history of URIs. Particularly, intervention was efficacious regardless of whether patients were infected with coronaviruses or not, thus generalizing results from a previous randomized trial with the same probiotic in adult patients with Covid19 (original Wuhan strain), also with specialist and molecular diagnosis. In said study, median symptom duration was shortened to 13 days vs. 18 in the placebo ( i.e. 5 less days, a 28% reduction) [ 13 ]. Our findings are also consistent with a recent study in pediatric URIs by Bettocchi et al., in which a probiotic mixture shortened the duration of fever from 5 days in the placebo group to 3 days in the treatment group, i.e. a 40% decrease [ 16 ]. Interestingly, the absolute reduction of the duration of symptoms seems to change depending on the natural duration of the URI, yet the percent of reduction seems more comparable across studies with probiotics. This shortening of symptoms is noteworthy as antipyretics do not seem to reduce the overall duration of the disease [ 17 ], suggesting specific probiotics could be an interesting add-on to current treatments for URIs. Lactiplantibacillus plantarum (formerly Lactobacillus plantarum ) and closely related Lactobacillaceae bacteria such as Pediococci, are common endophytes, living in wild vegetables and frequently ingested by herbivores and omnivores [ 18 ]. As such, the immune systems of the latter evolved under repeated intestinal exposure to the former, regardless of said bacteria behaving as nomadic commensals or successfully engrafting in the intestine ( i.e. becoming autochthonous). A seminal randomized trial in more than 4,000 newborns, comparing L. plantarum strain ATCC202195 to placebo, found a significant reduction in lower respiratory tract infections and sepsis [ 19 ]. The formula used in the current study, containing L. plantarum (strains KABP022, KABP023 and KABP033) and P. acidilactici (strain KABP021), was previously tested in a randomized clinical trial in 300 adults with PCR-confirmed, symptomatic Covid19, resulting in reduced duration of symptoms and viral load [ 13 ]. However, as the study population ranged 18 to 60 years old, evidence was missing in pediatric patients. Besides, in vitro studies found this same probiotic formula induced type-I interferon response in phagocytic cells [ 20 ]. Noteworthy, gut microbiota modulation of the host’s tonic type-I interferons seems to mediate systemic antiviral effects in mouse models [ 21 , 22 ]. In our study, a reduction in the incidence of nasal congestion and in the total number of symptoms per patient was also observed at two weeks, but not six weeks, after completing the 15-day intervention ( i.e. 30 days but not 60 days from baseline). Thus, immune-stimulating effects were seemingly maintained for a limited time once probiotic ingestion stopped, a finding deserving further investigations. Previous randomized trials of probiotics for URIs in children have mostly relied on parent/caregiver diagnosis [ 8 , 9 ]. This introduces a potential confounder, every patient in the study being diagnosed by a different, untrained person. In this regard, a recent large trial found no effect of L. rhamnosus DSM33153 ( a.k.a. ATCC53103) on URIs diagnosed by a physician and confirmed by laboratory tests [ 23 ], despite the same strain showing positive effects in previous trials that relied on parental diagnosis and did not identify etiologic agent [ 24 , 25 ]. Therefore, proper diagnosis by a physician and use of molecular methods seems relevant to increase the reliability of such clinical trials. Conversely, other recent probiotic studies relying on diagnosis by specialists alone [ 16 ] or specialist and molecular methods [ 26 ] found a significant effect against URIs, using different strains [ 16 , 26 ]. This apparent disparity may be explained by the fact that probiotic effects are often strain-specific, particularly immune-effects, and should not be extrapolated one strain to another [ 5 , 10 – 12 ]. In this regard, URI in our study were diagnosed by pediatricians based on clear clinical criteria (pharyngitis accompanied by fever) and confirmed by molecular method, thereby enhancing the robustness of our findings. No single causative agent dominated our study population. Rhinovirus (36.0%), coronaviruses (28.0%, two thirds being SARS-CoV2) and RSV (25.3%) were the most prevalent, in line with recent studies [ 3 , 4 ]. Human metapneumovirus (14.6%) and adenoviruses (10.7%) were moderately prevalent, while influenza, parainfluenza and human bocavirus had a prevalence < 10% each. A recent study in children found infections with rhinovirus, RSV or metapneumovirus resulted in higher severity and/or a risk of hospitalization, underscoring the importance of effective therapies for these viruses [ 27 ]. Of note, causative agents are seldom reported in URI trials with probiotics [ 16 , 24 , 25 ], yet their diversity introduces a potential confounder, unless properly accounted for: as the number of causative agents increases, so do the chances of a random imbalance between study groups (especially in moderately sized studies). Moreover, having several infectious agents in the same study entails the possibility of high efficacy against some viruses to mask low efficacy against others. Therefore, sensitivity analyses seem desirable to rule out such confounders. In this regard, our study is a first in probiotic research for URIs, to our knowledge. All adverse events (AEs) in the study were mild and of gastrointestinal (GI) type. Previous studies have noted that GI symptoms are common among URI patients [ 28 , 29 ]. In our study, several patients reported GI symptoms already at baseline. Unfortunately, such baseline info was not collected in a systematic, solicited manner, thus preventing a proper analysis of treatment-emergent AEs for all patients. Nevertheless, AE incidence did not differ between study groups, suggesting the probiotic intervention was well-tolerated. Several study limitations should be pointed out. First, several URI symptoms were rated as present/absent (instead of a severity scale), and were not required as entry criteria, thus reducing our capacity to detect differences between groups. A better assessment of these secondary endpoints could have been obtained with a more precise symptoms scale, such as the WURSS. However, the pediatric version of this scale has only been validated for children 4 years and older [ 30 ]. Second, a causative virus could not be identified in 10 patients (13.3%) despite using a large panel identifying up to 19 viruses. These cases could be false negatives, viruses not in our panel and/or bacterial infections resembling viral infections, yet they were fairly balanced between study groups. Third, the prevalence of common viruses such as influenza or adenoviruses was low in our population. Nevertheless, most prevalent viruses in our population coincided with a recent meta-analysis [ 4 ], and sensitivity analyses indicated efficacy in our study was not dependent on these prevalent viruses. Fourth, recording of highest daily temperature is affected by timing of the measurement, while FLACC score measures both pain and distress or discomfort [ 31 ] and is dependent on subjective assessment. However, the concurrent effect in both co-primary endpoints, below the multiplicity-adjusted threshold of p = 0.025, helps strengthen our conclusions. Moreover, days of use of ibuprofen markedly correlated with both endpoints, adding internal validity. Finally, no fecal microbiota analysis was included in our study. However, the previous randomized trial with the same probiotic found significant clinical effects despite no significant taxonomical changes in fecal microbiota [ 13 ], akin to other publications [ 32 ]. In conclusion, our study suggests the specific probiotic formula containing strains P. acidilactici KABP021 and L. plantarum KABP022, KABP023 and KABP033 helps shorten the duration of fever and pain/discomfort in children with URI with pharyngitis of diverse viral origin. This formula may also reduce the severity of relapses or new infections for a limited time after completing the intervention. Said results warrant replication in larger, multi-centric, randomized trials. Abbreviations AE Adverse Event; AUC Area Under the Curve; CFU Colony-Forming units; CONSORT Consolidated Standards of Reporting Trials; FLACC Face, Legs, Activity, Crying and Consolability; GLM Generalized Linear Model; RSV Respiratory Syncytial Virus; SPSS Statistical Package for the Social Sciences; URI Upper Respiratory Infection. Declarations Funding This work was fully sponsored by AB-Biotics, S.A (Kaneka Corp.). Competing Interests JE-M, JVC and MR-P are full-time employees of AB-Biotics SA (Kaneka Group), the company that funded the study. DA-P and MGM-F declare no competing interests for this work. Ethics approval: The study was conducted in accordance with the Declaration of Helsinki, and approval was obtained from Hospital Medica Sur research ethics boards. Consent to participate: Parents of all participants provided written informed consent. Author Contribution DA-P, JE-M and MR-P conceptualized and designed the study. DA-P and MGM-F recruited and treated patients, and collected data. JE-M analyzed the data. JE-M and JVC drafted the initial manuscript. DA-P and MR-P critically reviewed the manuscript. All authors approved the final manuscript as submitted. Data availability: All data used in the current publication are available (duly anonymized) from the corresponding author upon reasonable request. References Sirota SB, Doxey MC, Dominguez R-MV, Bender RG, Vongpradith A, Albertson SB, Novotney A, Burkart K, et al (2024) Global, regional, and national burden of upper respiratory infections and otitis media, 1990–2021: a systematic analysis from the Global Burden of Disease Study 2021. Lancet Infect Dis. https://doi.org/10.1016/S1473-3099(24)00430-4 Laurent GJ, Shapiro SD (2006) Encyclopedia of Respiratory Medicine, 1st ed. Academic Press Inc. 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Cochrane Database Syst Rev 8:. https://doi.org/10.1002/14651858.CD006895.PUB4 Paineau D, Carcano D, Leyer G, Darquy S, Alyanakian MA, Simoneau G, Bergmann JF, Brassart D, et al (2008) Effects of seven potential probiotic strains on specific immune responses in healthy adults: A double-blind, randomized, controlled trial. FEMS Immunol Med Microbiol 53:107–113. https://doi.org/10.1111/j.1574-695X.2008.00413.x van Hemert S, Meijerink M, Molenaar D, Bron PA, de Vos P, Kleerebezem M, Wells JM, Marco ML (2010) Identification of Lactobacillus plantarum genes modulating the cytokine response of human peripheral blood mononuclear cells. BMC Microbiol 10:293. https://doi.org/10.1186/1471-2180-10-293 Meijerink M, van Hemert S, Taverne N, Wels M, de Vos P, Bron PA, Savelkoul HF, van Bilsen J, et al (2010) Identification of genetic loci in Lactobacillus plantarum that modulate the immune response of dendritic cells using comparative genome hybridization. PLoS One 5:e10632. https://doi.org/10.1371/journal.pone.0010632 Gutiérrez-Castrellón P, Gandara-Martí T, Abreu Y Abreu AT, Nieto-Rufino CD, López-Orduña E, Jiménez-Escobar I, Jiménez-Gutiérrez C, López-Velazquez G, et al (2022) Probiotic improves symptomatic and viral clearance in Covid19 outpatients: a randomized, quadruple-blinded, placebo-controlled trial. Gut Microbes 14:. https://doi.org/10.1080/19490976.2021.2018899 Merkel S, Voepel-Lewis T, Shayevitz J, Malviya S (1997) The FLACC: a behavioral scale for scoring postoperative pain in young children. Pediatr Nurs 23:293–297 Agresti A (2006) An Introduction to Categorical Data Analysis: Second Edition. An Introduction to Categorical Data Analysis: Second Edition 1–356. https://doi.org/10.1002/0470114754 Bettocchi S, Comotti A, Elli M, Cosmi V De, Berti C, Alberti I, Mazzocchi A, Rosazza C, et al (2025) Probiotics and Fever Duration in Children With Upper Respiratory Tract Infections: A Randomized Clinical Trial. JAMA Netw Open 8:e250669–e250669. https://doi.org/10.1001/JAMANETWORKOPEN.2025.0669 Nicolas M, Sun S, Zorzi F, Deplace S, Jaafari N, Boussageon R (2023) Does the use of antipyretics prolong illness? A systematic review of the literature and meta-analysis on the effects of antipyretics in acute upper and lower respiratory tract infections. Infect Dis Now 53 Martínez-Romero E, Aguirre-Noyola JL, Bustamante-Brito R, González-Román P, Hernández-Oaxaca D, Higareda-Alvear V, Montes-Carreto LM, Martínez-Romero JC, et al (2020) We and herbivores eat endophytes. Microb Biotechnol 0:1–18. https://doi.org/10.1111/1751-7915.13688 Panigrahi P, Parida S, Nanda NC, Satpathy R, Pradhan L, Chandel DiS, Baccaglini L, Mohapatra A, et al (2017) A randomized synbiotic trial to prevent sepsis among infants in rural India. Nature 548:407–412. https://doi.org/10.1038/nature23480 Altadill T, Armengol E, Espadaler-Mazo J (2024) Abstract 1263 Probiotic blend of L.plantarum and P.acidilactici (AB21) stimulates type-I interferon response in phagocytes with the participation of the IRF7 transcription factor, possibly involving both MyD88-dependent and independent mechanisms. Journal of Biological Chemistry 300:105827. https://doi.org/10.1016/j.jbc.2024.105827 Winkler ES, Shrihari S, Hykes BL, Handley SA, Andhey PS, Huang YJS, Swain A, Droit L, et al (2020) The Intestinal Microbiome Restricts Alphavirus Infection and Dissemination through a Bile Acid-Type I IFN Signaling Axis. Cell 182:901-918.e18. https://doi.org/10.1016/J.CELL.2020.06.029 Bradley KC, Finsterbusch K, Schnepf D, Crotta S, Llorian M, Davidson S, Fuchs SY, Staeheli P, et al (2019) Microbiota-Driven Tonic Interferon Signals in Lung Stromal Cells Protect from Influenza Virus Infection. Cell Rep 28:245-256.e4. https://doi.org/10.1016/j.celrep.2019.05.105 Damholt A, Keller MK, Baranowski K, Brown B, Wichmann A, Melsaether C, Eskesen D, Westphal V, et al (2022) Lacticaseibacillus rhamnosus GG DSM 33156 effects on pathogen defence in the upper respiratory tract: a randomised, double-blind, placebo-controlled paediatric trial. Benef Microbes 13:13–23. https://doi.org/10.3920/BM2021.0065 Hatakka K, Savilahti E, Pönkä A, Meurman JH, Poussa T, Näse L, Saxelin M, Korpela R (2001) Effect of long term consumption of probiotic milk on infections in children attending day care centres: double blind, randomised trial. BMJ 322:1327–1329. https://doi.org/10.1136/BMJ.322.7298.1327 Hojsak I, Snovak N, Abdović S, Szajewska H, Mišak Z, Kolaček S (2010) Lactobacillus GG in the prevention of gastrointestinal and respiratory tract infections in children who attend day care centers: A randomized, double-blind, placebo-controlled trial. Clinical Nutrition 29:312–316. https://doi.org/10.1016/j.clnu.2009.09.008 Maya-Barrios A, Lira-Hernandez K, Jiménez-Escobar I, Hernández L, Ortiz-Hernandez A, Jiménez-Gutiérrez C, López-Velázquez G, Gutiérrez-Castrellón P (2021) Limosilactobacillus reuteri ATCC PTA 5289 and DSM 17938 as adjuvants to improve evolution of pharyngitis/tonsillitis in children: randomised controlled trial . Benef Microbes 12:137–145. https://doi.org/10.3920/BM2020.0171 Windsor WJ, Lamb MM, Dominguez SR, Mistry RD, Rao S (2022) Clinical characteristics and illness course based on pathogen among children with respiratory illness presenting to an emergency department. J Med Virol 94:6103–6110. https://doi.org/10.1002/JMV.28031 Minodier L, Masse S, Capai L, Blanchon T, Ceccaldi PE, van der Werf S, Hanslik T, Charrel R, et al (2017) Clinical and virological factors associated with gastrointestinal symptoms in patients with acute respiratory infection: a two-year prospective study in general practice medicine. BMC Infect Dis 17:. https://doi.org/10.1186/S12879-017-2823-9 Newman KL, Wolf CR, Logue JK, Englund JA, Boeckh M, Chu HY (2023) Nausea, Vomiting, and Diarrhea Are Common in Community-Acquired Acute Viral Respiratory Illness. Dig Dis Sci 68:3383–3389. https://doi.org/10.1007/S10620-023-07976-4 Schmit KM, Brown R, Hayer S, Checovich MM, Gern JE, Wald ER, Barrett B (2021) Wisconsin Upper Respiratory Symptom Survey for Kids: Validation of an Illness-specific Quality of Life Instrument. Pediatr Res 90:1207–1214. https://doi.org/10.1038/S41390-021-01395-9 Babl FE, Crellin D, Cheng J, Sullivan TP, O’Sullivan R, Hutchinson A (2012) The use of the faces, legs, activity, cry and consolability scale to assess procedural pain and distress in young children. Pediatr Emerg Care 28:1281–1286. https://doi.org/10.1097/PEC.0B013E3182767D66 Wieërs G, Belkhir L, Enaud R, Leclercq S, Foy J-MP de, Dequenne I, Timary P de, Cani PD (2019) How Probiotics Affect the Microbiota. Front Cell Infect Microbiol 9:454. https://doi.org/10.3389/FCIMB.2019.00454 Additional Declarations Competing interest reported. JE-M, JVC and MR-P are full-time employees of AB-Biotics SA (Kaneka Group), the company that funded the study. DA-P and MGM-F declare no competing interests for this work. Supplementary Files SupplementaryMaterialEurJPed.docx CONSORTChecklistEurJPed.pdf Cite Share Download PDF Status: Published Journal Publication published 26 Nov, 2025 Read the published version in European Journal of Pediatrics → Version 1 posted Editorial decision: Revision requested 09 Sep, 2025 Reviews received at journal 08 Sep, 2025 Reviewers agreed at journal 04 Aug, 2025 Reviews received at journal 03 Aug, 2025 Reviewers agreed at journal 28 Jul, 2025 Reviewers invited by journal 28 Jul, 2025 Editor assigned by journal 27 Jul, 2025 Submission checks completed at journal 27 Jul, 2025 First submitted to journal 25 Jul, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7214019","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":494254626,"identity":"edcb0405-222c-413c-902d-6ab0a40d9ca9","order_by":0,"name":"Diana M. Andrade-Platas","email":"","orcid":"","institution":"Hospital Medica Sur","correspondingAuthor":false,"prefix":"","firstName":"Diana","middleName":"M.","lastName":"Andrade-Platas","suffix":""},{"id":494254627,"identity":"598ed844-597f-4fd7-bf46-2229b6a250a7","order_by":1,"name":"Marta Gloria Martinez-Figueroa","email":"","orcid":"","institution":"Hospital Medica Sur","correspondingAuthor":false,"prefix":"","firstName":"Marta","middleName":"Gloria","lastName":"Martinez-Figueroa","suffix":""},{"id":494254628,"identity":"c84f1b82-c271-451b-9a8e-e5656d1beb51","order_by":2,"name":"Maria Rodriguez-Palmero","email":"","orcid":"","institution":"AB-Biotics SA (Kaneka Group)","correspondingAuthor":false,"prefix":"","firstName":"Maria","middleName":"","lastName":"Rodriguez-Palmero","suffix":""},{"id":494254629,"identity":"12ad257a-729b-455a-a9ee-1381df34eeda","order_by":3,"name":"Jose Vicente Carratalá","email":"","orcid":"","institution":"AB-Biotics SA (Kaneka Group)","correspondingAuthor":false,"prefix":"","firstName":"Jose","middleName":"Vicente","lastName":"Carratalá","suffix":""},{"id":494254630,"identity":"7ff7f66c-c024-4c16-abb2-0b222d906aa5","order_by":4,"name":"Jordi Espadaler-Mazo","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+UlEQVRIiWNgGAWjYLACHgYLBgb2BjYGxgYJBgZm4rQAVfIcgGjhIV6LRAJIC4hDAPDznz344U2NhJz5zMfPHjDusJCzZ2d+/IGhxiYalxbJGXnJknOOSRjL3E4zN2A8I2HMw8xmJsFwLC23AYcWgxs8BtI8bBKJM6QTzKT/tkkk9jDzgFx4GKcW+/NnjH/z/JOonyF5/JsEI0QL8wd8WgwYcsykedskEiQkeMxgWhgk8GmRuJGXZjm3T8JwBk9OOcQvh4F+ScDjF/7+s4dvvPlmIy/BfnwbMMTq5Nj7Dz/+8KHGBqcWHPGQgFM5Ti2jYBSMglEwCpAAAF1ATGWcftw6AAAAAElFTkSuQmCC","orcid":"","institution":"AB-Biotics SA (Kaneka Group)","correspondingAuthor":true,"prefix":"","firstName":"Jordi","middleName":"","lastName":"Espadaler-Mazo","suffix":""}],"badges":[],"createdAt":"2025-07-25 11:53:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7214019/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7214019/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00431-025-06587-7","type":"published","date":"2025-11-26T15:58:06+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":88223573,"identity":"d3860c9f-26c1-4988-b7ac-c1134c490931","added_by":"auto","created_at":"2025-08-04 08:11:52","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":141157,"visible":true,"origin":"","legend":"\u003cp\u003eParticipant CONSORT flow diagram.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7214019/v1/d872bc0291b7ccfc8d8dab27.jpeg"},{"id":88223753,"identity":"7e833529-5208-4817-be63-80a00811f59d","added_by":"auto","created_at":"2025-08-04 08:19:52","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":94227,"visible":true,"origin":"","legend":"\u003cp\u003ePrimary outcomes: baseline-adjusted means (and 95%CI) for days of fever (defined as axillary temperature \u0026gt;37.5ºC, left) and days of pain/discomfort (defined as FLACC score \u0026gt;3, right) during the intervention period, together with summary results of their generalized linear models (GLMs). Analysis per intent-to-treat by allocated group (placebo n=38, probiotic n=37).\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7214019/v1/9305e5ace54df1a9042b558b.jpeg"},{"id":97179625,"identity":"fc25e2a1-434a-4e90-9aa9-0402604bc5e8","added_by":"auto","created_at":"2025-12-01 16:16:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1095165,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7214019/v1/fbd7ae87-db0d-4b45-88a2-d8636fbab13d.pdf"},{"id":88223571,"identity":"d87d356d-35e5-45ec-aba8-6bdf974b186a","added_by":"auto","created_at":"2025-08-04 08:11:52","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":270831,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterialEurJPed.docx","url":"https://assets-eu.researchsquare.com/files/rs-7214019/v1/820de388df590ab0d064227b.docx"},{"id":88223568,"identity":"6b91f502-947d-4562-ad40-0a40cdfda95a","added_by":"auto","created_at":"2025-08-04 08:11:52","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":66162,"visible":true,"origin":"","legend":"","description":"","filename":"CONSORTChecklistEurJPed.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7214019/v1/632529822d888bea61a278d3.pdf"}],"financialInterests":"Competing interest reported. JE-M, JVC and MR-P are full-time employees of AB-Biotics SA (Kaneka Group), the company that funded the study. DA-P and MGM-F declare no competing interests for this work.","formattedTitle":"\u003cp\u003eA Probiotic Containing L. Plantarum and P. Acidilactici Strains for Treating Upper Respiratory Infection in Children Aged 6 Months to 5 Years: A Randomized, Double-Blind Trial \u003c/p\u003e","fulltext":[{"header":"What is known","content":"\u003cp\u003eAcute upper respiratory tract infections (URIs) are highly prevalent in children, but due to their frequent viral etiology, treatment is often symptomatic only. Some probiotics have shown promising results against URIs, but evidence mostly relies on untrained, subjective diagnosis by participants or their parents. Recently, a probiotic formula containing strains \u003cem\u003eL. plantarum\u003c/em\u003e KABP022, KABP023 and KABP033, and \u003cem\u003eP. acidilactici\u003c/em\u003e KABP021 reduced viral load and duration of symptoms in a randomized trial in 300 adults with laboratory-confirmed Covid19, against placebo.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is New:\u003c/strong\u003e In children with URI with pharyngitis, as diagnosed by a specialist, intervention with said probiotic formula reduced the duration both of fever and of pain/discomfort, compared to placebo. Results were robust to sensitivity analyses by age, sex, number of recent URIs and by most prevalent causative viruses in the study population.\u003c/p\u003e"},{"header":"Introduction","content":"\u003cp\u003eAcute upper respiratory tract infections (URIs) are highly prevalent, especially in children [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Clinical symptoms are usually self-limited, but occasionally the infection spreads to adjacent organs, yielding more serious clinical manifestations [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. URIs reduce quality of life for the affected children and their parents, and result in medical and non-medical costs. Causative agents in children are mainly viruses, the most prevalent since the onset of the Covid19 pandemic being rhinoviruses, respiratory syncytial virus (RSV) and SARS-CoV2 [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Lack of antiviral therapies against most URI viruses usually limits treatment to symptom management (\u003cem\u003ee.g.\u003c/em\u003e antipyretics, antihistamines).\u003c/p\u003e\u003cp\u003eProbiotics are defined as “live microorganisms that when administered in adequate amounts, confer a health benefit on the host” [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Mounting evidence indicates a crosstalk between the gastro-intestinal tract and the respiratory system, along with their respective microbiomes, referred to as the gut-lung axis [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. In this regard, recent meta-analyses found oral probiotics may help prevent or shorten upper respiratory infections such as cold and influenza, but also noted significant limitations, such as high heterogeneity, overreliance on subjective diagnosis and unclear treatment concealment [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Of note, heterogeneity is not unexpected, as probiotic immune effects are considered to be strain-specific [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e–\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe AB21® probiotic formula includes four strains of the Lactobacillaceae family: \u003cem\u003eLactiplantibacillus plantarum\u003c/em\u003e KABP022, KABP023 and KABP033, plus \u003cem\u003ePediococcus acidilactici\u003c/em\u003e KABP021. A previous randomized clinical trial in 300 adult patients found this formula improved PCR-confirmed Covid19, according both to objective signs (\u003cem\u003ee.g.\u003c/em\u003e viral load, digital chest X-ray) and subjective symptoms [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. However, evidence of its effect against other viruses and in the pediatric population was lacking. In this study, we aimed to test the efficacy and safety of the same probiotic formula in shortening the duration of specialist-diagnosed URIs of viral origin, in a pediatric population.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cb\u003eStudy design and setting\u003c/b\u003e\u003c/p\u003e\u003cp\u003eWe conducted a randomized, single-center, double-blind, placebo-controlled trial with two parallel arms. The study was conducted at Hospital Medica Sur (Mexico City, Mexico). Approval was duly obtained from the hospital’s Committee for Ethics and Research in Studies in Humans (approval ref. CB148-CEI153). The study adhered to the tenets of the Declaration of Helsinki, was prospectively registered as ISRCTN-66122782 and is reported according to Consolidated Standards of Reporting Trials (CONSORT).\u003c/p\u003e\u003cp\u003e\u003cb\u003eParticipants\u003c/b\u003e\u003c/p\u003e\u003cp\u003eWe included pediatric participants, aged 6 months to 5 years, with an upper respiratory infection with fever and pharyngitis, as diagnosed by a pediatrician, and symptoms’ onset within 48h of enrolment. Parents had to report the child experiencing fever (\u0026gt; 37.5ºC) and a FLACC score (Face, Legs, Activity, Crying and Consolability) \u0026gt; 3 [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], and to provide written informed consent. Exclusion criteria were: i) Symptoms suggestive of bacterial infection (tonsillitis or tonsillar exudate, cervical lymphadenitis, otitis media or scarlatiniform rash); ii) preterm infants or those weighting \u0026lt; 2500gr at birth; iii) failure to thrive (as per WHO standards); iv) use of antibiotics, antivirals or probiotics for \u0026gt; 48h within 2 weeks of study entry (applied to infants and mothers of breastfed participants); v) history of ≥ 2 invasive infections (meningitis, osteomyelitis, sepsis); vi) history of recurrent, severe respiratory infections (upper or lower) within 12 months of study entry; vii) chronic diarrhea or gastroesophageal reflux disease; viii) congenital heart, respiratory or digestive disease; ix) primary or secondary immunodeficiency; and, x) asthma.\u003c/p\u003e\u003cp\u003e\u003cb\u003eProcedures\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe study consisted of a 15-day intervention phase (Visits 1 to 2) plus a 45-day follow-up phase (Visits 3 and 4, Supplementary Fig.\u0026nbsp;1). A computer-generated 1:1 (probiotic:placebo) randomization list, of block size 4, was prepared by personnel not directly participating in the study and kept in a sealed envelope until study completion. Study investigators recruited and allocated patients and performed all study procedures. Investigators, parents and pediatric participants were blinded to treatment allocation. Probiotic and placebo capsules looked identical, both contained an off-white powder, and both were delivered in undistinguishable, anonymous boxes.\u003c/p\u003e\u003cp\u003eAt Visit 1 (baseline, day 0), parents of eligible participants who provided informed consent received the allocated intervention and were briefed both on product administration and use of the patient diary for daily recording of: i) symptoms (axillary temperature (ºC), FLACC score, and presence/absence of each of cough, rhinorrhea and nasal congestion); ii) comedication; and iii) adverse events (AEs). A nasopharyngeal swab (Copan, Italy) was taken and stored at -20ºC in Universal Transport Medium for posterior analysis of causative agents. At Visit 2 (day 15 from enrolment), patient diaries were returned, investigators verified study compliance and assessed clinical status of participants and unsolicited AEs. Clinical status of participants and unsolicited AEs were assessed again during follow-up at Visits 3 and 4 (30 and 60 days from enrolment ± 3 days, respectively). Analysis of causative agents was performed in batch at Grupo Diagnostico Aries (Mexico), using the Respiratory Flow multiplex PCR (Vitro SA, Spain).\u003c/p\u003e\u003cp\u003e\u003cb\u003eInterventions\u003c/b\u003e\u003c/p\u003e\u003cp\u003eAll treatments were taken orally. Probiotic or equally looking placebo were taken twice daily (morning and evening). Probiotic capsules contained lyophilized \u003cem\u003ePediococcus acidilactici\u003c/em\u003e strain KABP021 (CECT7483) and \u003cem\u003eLactiplantibacillus plantarum\u003c/em\u003e strains KABP022 (CECT7484), KABP023 (CECT7485) and KABP033 (CECT30292), totaling ≥ 2\u0026nbsp;billion CFUs (colony-forming units, as per plate counting in MRS medium), in a dextrin carrier. Placebo capsules contained the dextrin carrier only. Microbial quality was verified as described elsewhere [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Parents were instructed to open the capsules and dissolve the content in water or lukewarm milk, right before administration.\u003c/p\u003e\u003cp\u003eStudy participants could also receive standard of care for pediatric URIs, consisting of ibuprofen as antipyretic drug (10 mg/Kg of body weight per day) and/or cetirizine as antihistamine drug (0.25 mg/Kg of body weight per day) as rescue medication. Should study participants develop symptoms of bacterial infection after study entry, investigators could prescribe rescue antibiotics: amoxicillin clavulanate (at 45mg/Kg of body weight per day), or clarithromycin (at 7.5 mg/Kg of body weight per day) in case of allergy to beta-lactams. No antivirals were used during the study.\u003c/p\u003e\u003cp\u003e\u003cb\u003ePredefined outcomes\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe co-primary study outcomes were the number of days with fever (\u003cem\u003ei.e.\u003c/em\u003e highest daily axillary temperature \u0026gt; 37.5ºC) and the number of days with pain/discomfort score \u0026gt; 3 (as measured with the FLACC score)[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] during the intervention period. Secondary outcomes included: i) Area Under the Curve (AUC) of body temperature and FLACC score during the intervention period; ii) number of days with cough, nasal congestion, rhinorrhea, use of antipyretic (ibuprofen), use of antihistamine (cetirizine) and use of antibiotics, during the intervention period; iii) number of unscheduled medical visits during the intervention period as reported by parents at Visit 2; iv) occurrence of each of the different symptoms (axillary temperature \u0026gt; 37.5ºC, FLACC \u0026gt; 3, cough, rhinorrhea and nasal congestion) and their total number, as assessed by investigators at Visits 3 and 4; v) number of unscheduled medical visits as reported by parents at Visits 3 and 4. Because participants attended Visit 2 (day 15) at different times of the day (morning, afternoon or evening), only data from finished days (\u003cem\u003ei.e.\u003c/em\u003e 1 to 14) was used in outcomes related to the intervention period to ensure comparability between participants.\u003c/p\u003e\u003cp\u003e\u003cb\u003ePower calculation and statistical analysis\u003c/b\u003e\u003c/p\u003e\u003cp\u003eSample size was calculated to allow detecting a difference in duration of 1 day with a standard deviation (SD) of 1.2 days, a statistical power of 90% and alpha of 2.5% (\u003cem\u003ei.e.\u003c/em\u003e multiplicity-adjusted for two co-primary endpoints), leading to 36 participants per group. This number was increased to 45 per group to allow for a drop-out rate of 20%.\u003c/p\u003e\u003cp\u003eStatistical analysis was performed on all randomized patients (intent-to-treat) by allocated group, using IBM SPSS Statistics program (version 22). Differences in baseline characteristics between groups were not formally assessed using p-values, following CONSORT 2010 and European Medicines Agency (EMA) guidelines. Differences between study groups for the co-primary endpoints (days of highest axillary temperature \u0026gt; 37.5ºC and of FLACC score \u0026gt; 3) were assessed with generalized linear models (GLM), with baseline temperature or FLACC score as covariates (respectively); normality of residuals was verified by Q-Q plots. Differences between groups for secondary endpoints were assessed by Mann-Whitney test (exact version) for continuous or ordinal data, and Chi-Squared test (with N-1 correction)[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] for categorical data. In exploratory analyses, GLMs for the co-primary endpoints were adjusted for detection rhinovirus (yes/no), detection of coronaviruses (yes/no), detection of RSV (yes/no), age (up to 12 months \u003cem\u003evs\u003c/em\u003e. older), sex (male/female) and number of URIs in the previous two months. Spearman test was used to assess bivariate correlations. All tests were two-sided.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cb\u003eParticipants\u003c/b\u003e\u003c/p\u003e\u003cp\u003eFrom October 2022 to February 2023, 75 pediatric participants were recruited, underwent the 15-day intervention and were followed-up until the last study visit, 2 months from randomization (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). As no dropouts were observed, recruitment was stopped before reaching 90 participants once target statistical power was achieved for the co-primary outcomes. Median age was 15 months and 39 (52.0%) were female. Other than fever (\u0026gt;\u0026thinsp;37.5\u0026ordm;C) and a FLACC score\u0026thinsp;\u0026gt;\u0026thinsp;3 as per entry criteria, the most common URI symptom was rhinorrhea (82.7%), and most participants were already taking ibuprofen (93.3%). Baseline characteristics were well-balanced between study groups (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eBaseline characteristics of study participants.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePlacebo (n\u0026thinsp;=\u0026thinsp;38)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eProbiotic (n\u0026thinsp;=\u0026thinsp;37)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge (months; median, range)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14.5 (6\u0026ndash;59)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e15.0 (6\u0026ndash;53)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWeight at birth (Kg; mean, SD)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3.16 (0.25)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.23 (0.31)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSex (female; N, %)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e16 (42,1%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20 (54,1%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBorn by C-section (N, %)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e16 (43.2%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e14 (37.5%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBreastfed until 6 months of age (N, %)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e32 (84.2%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e32 (86.5%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCompleted scheduled vaccines by age (N, %)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e38 (100%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e37 (100%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCurrent weight (Kg; median, range)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10.1 (6.8\u0026ndash;24.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10.1 (6.5\u0026ndash;22.1)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCurrently attending kindergarten (N, %)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e32 (84.2%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e29 (78.4%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNumber of URIs within two months (mean, SD)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.5 (1.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.8 (0.8)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBody temperature at baseline (\u0026ordm;C; mean, SD)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e37.8 (0.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e37.7 (0.8)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFLACC score at baseline (median, range)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8.0 (4\u0026ndash;9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.0 (4\u0026ndash;9)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresence of other URI symptoms baseline:\u003c/p\u003e\u003cp\u003e\u0026bull; Rhinorrhea (N, %)\u003c/p\u003e\u003cp\u003e\u0026bull; Nasal congestion (N, %)\u003c/p\u003e\u003cp\u003e\u0026bull; Cough (N, %)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026nbsp; \u003c/p\u003e\u003cp\u003e33 (86.8%)\u003c/p\u003e\u003cp\u003e22 (57.9%)\u003c/p\u003e\u003cp\u003e22 (57.9%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026nbsp; \u003c/p\u003e\u003cp\u003e29 (78.4%)\u003c/p\u003e\u003cp\u003e20 (54.1%)\u003c/p\u003e\u003cp\u003e22 (59.5%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUsing antipyretics at baseline (N, %)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e35 (92.1%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e35 (94.6%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUsing antihistamines at baseline (N, %)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e12 (31.6%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10 (27.0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHours since the onset of symptoms (mean, SD)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e21.8 (11.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22.2 (12.0)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOxygen saturation at baseline (SpO\u003csub\u003e2\u003c/sub\u003e; mean, SD)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e95.4 (1.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95.0 (1.8)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNumber of viruses detected (mean, SD)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.4 (1.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.3 (0.8)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eAll patients provided nasopharyngeal swabs. Most frequent etiologic agents were rhinoviruses (36.0%), coronaviruses (28.0%, mostly SARS-CoV2) and respiratory syncytial virus (RSV, 25.3%). Several patients were positive for more than one virus. Overall distribution of viruses did not differ between study groups (\u003cb\u003eSupplementary Fig.\u0026nbsp;1\u003c/b\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003ePrimary Outcomes\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThere were 1.1 less days of fever (95%CI 0.5 to 1.7; p\u0026thinsp;=\u0026thinsp;0.001) and 0.7 days less of pain/discomfort (95%CI 0.2 to 1.2; p\u0026thinsp;=\u0026thinsp;0.006) in the probiotic group, compared to placebo (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Higher temperature and FLACC score at study entry resulted in more days of fever and of pain/discomfort, respectively (\u003cem\u003ei.e.\u003c/em\u003e baseline effect, both p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eSecondary Outcomes\u003c/b\u003e\u003c/p\u003e\u003cp\u003eDuring the intervention phase, AUC for body temperature and FLACC score were significantly lower in probiotic group \u003cem\u003evs.\u003c/em\u003e placebo (both p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), but no differences were found in the duration of other symptoms (rhinorrhea, nasal congestion and cough). Likewise, days of use of antipyretic and of antihistamine did not differ between study groups. During the six-week follow-up phase, incidence of nasal congestion and total number of symptoms were significantly lower in probiotic group at Visit 3 compared to placebo (\u003cem\u003ei.e.\u003c/em\u003e 15 days after completing the intervention, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), but not at Visit 4. Noteworthy, all participants displaying symptoms at Visit 3 had already achieved axillary temperature\u0026thinsp;\u0026lt;\u0026thinsp;37.5\u0026ordm;C and a FLACC score of 0 at Visit 2. The complete list of secondary endpoints is reported on Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSecondary outcomes. Median (range) or number of participants (% within group).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePlacebo (n\u0026thinsp;=\u0026thinsp;38)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eProbiotic (n\u0026thinsp;=\u0026thinsp;37)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntervention phase (reported at Visit 2)\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAUC temperature (\u0026ordm;C)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e517 (505\u0026ndash;525)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e515 (505\u0026ndash;522)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e0.021\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAUC FLACC score\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e39.5 (10.0-53.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e31.0 (7.0\u0026ndash;51.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e0.002\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDays with cough\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (0\u0026ndash;14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2 (0\u0026ndash;13)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.488\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDays with nasal congestion\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.5 (0\u0026ndash;12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1 (0\u0026ndash;12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.522\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDays with rhinorrhea\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7 (0\u0026ndash;13)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5 (0\u0026ndash;13)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.267\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDays of use of antipyretic (ibuprofen)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (2\u0026ndash;7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4 (2\u0026ndash;6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.108\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDays of use of antihistamine (cetirizine)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5.5 (0\u0026ndash;12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4 (0\u0026ndash;13)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.630\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParticipants using antibiotics\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (2.6%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.324\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParticipants with emergency medical visits\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.000\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eFollow-up days 16 to 30 (reported at Visit 3)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresence of fever (\u0026gt;\u0026thinsp;37.5 \u0026ordm;C)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7 (18.4%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4 (10.8%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.355\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresence of pain/discomfort (FLACC\u0026thinsp;\u0026gt;\u0026thinsp;3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7 (18.4%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5 (13.5%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.565\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresence of cough\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2 (5.3%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2 (5.4%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.978\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresence of nasal congestion\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7 (18.4%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1 (2.7%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e0.029\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresence of rhinorrhea\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8 (21.1%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4 (10.8%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.230\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNumber of symptoms\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (2\u0026ndash;5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3 (1\u0026ndash;4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e0.019\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParticipants with emergency medical visits\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (2.6%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.324\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eFollow-up days 31 to 60 (reported at Visit 4)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresence of fever (\u0026gt;\u0026thinsp;37.5 \u0026ordm;C)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8 (21.1%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9 (24.3%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.783\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresence of pain/discomfort (FLACC\u0026thinsp;\u0026gt;\u0026thinsp;3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8 (21.1%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9 (24.3%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.737\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresence of cough\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10 (26.3%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5 (13.5%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.169\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresence of nasal congestion\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7 (18.4%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9 (24.3%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.535\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresence of rhinorrhea\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8 (21.1%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10 (27.0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.547\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNumber of symptoms\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5 (1\u0026ndash;5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4 (1\u0026ndash;5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.215\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParticipants with emergency medical visits\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1 (2.7%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.311\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003ea) Data from patient diaries, except for number of emergency medical visits; b) Among symptom-positive participants at Visit 3 (probiotic n\u0026thinsp;=\u0026thinsp;6, placebo n\u0026thinsp;=\u0026thinsp;8); c) Among symptom-positive participants at Visit 4 (probiotic n\u0026thinsp;=\u0026thinsp;13, placebo n\u0026thinsp;=\u0026thinsp;11).\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eExploratory Outcomes\u003c/b\u003e\u003c/p\u003e\u003cp\u003ePost-hoc analyses were conducted to assess the impact of the most frequently detected viruses (rhinovirus, coronaviruses and RSV), age, sex and number of recent URIs (ranging 0 to 3) on co-primary endpoints. Probiotic intervention was still superior to placebo after adjusting for each of these factors, both for fever and for pain/discomfort (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01, \u003cb\u003eSupplementary Table\u0026nbsp;1\u003c/b\u003e). Patients positive for coronaviruses (n\u0026thinsp;=\u0026thinsp;21) had 0.7 more days of fever on average (p\u0026thinsp;=\u0026thinsp;0.041). Conversely, patients positive for RSV (n\u0026thinsp;=\u0026thinsp;19) had 0.8 more days of pain/discomfort on average (p\u0026thinsp;=\u0026thinsp;0.004). Other variables assessed did not influence the duration of fever or pain. Days of use of antipyretic correlated with days of fever (rho\u0026thinsp;=\u0026thinsp;0.56, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and of pain/discomfort (rho\u0026thinsp;=\u0026thinsp;0.71, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), while days of use of antihistamine correlated with days of rhinorrhea (rho\u0026thinsp;=\u0026thinsp;0.85, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Days of fever and of pain/discomfort markedly correlated one another (rho\u0026thinsp;=\u0026thinsp;0.78, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), while days of rhinorrhea and of congestion mildly correlated one another (rho\u0026thinsp;=\u0026thinsp;0.26, p\u0026thinsp;=\u0026thinsp;0.022). Bivariate correlations can be found on \u003cb\u003eSupplementary Table\u0026nbsp;2\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e\u003cb\u003eSafety\u003c/b\u003e\u003c/p\u003e\u003cp\u003eNo severe AEs or hospitalizations were reported during the study. All reported AEs were of gastrointestinal type, mild and self-limited, and their numbers did not differ between study groups (\u003cb\u003eSupplementary Table\u0026nbsp;3\u003c/b\u003e).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this randomized, placebo-controlled study, probiotic intervention was associated with a shorter duration of fever and pain/discomfort, in children with an upper respiratory infection (URI) of likely viral origin with pharyngitis, as diagnosed by a pediatrician. On average, the duration of fever was shortened to 1.6 days \u003cem\u003evs.\u003c/em\u003e 2.7 in the placebo (\u003cem\u003ei.e.\u003c/em\u003e 1.1 less days, a 40% reduction), and pain/discomfort was shortened to 3.7 days \u003cem\u003evs\u003c/em\u003e. 4.4 in the placebo (\u003cem\u003ei.e.\u003c/em\u003e 0.7 less days, a 19% reduction). Results were robust to a variety of sensitivity analyses, including type of virus and participant\u0026rsquo;s age, sex and recent history of URIs. Particularly, intervention was efficacious regardless of whether patients were infected with coronaviruses or not, thus generalizing results from a previous randomized trial with the same probiotic in adult patients with Covid19 (original Wuhan strain), also with specialist and molecular diagnosis. In said study, median symptom duration was shortened to 13 days \u003cem\u003evs.\u003c/em\u003e 18 in the placebo (\u003cem\u003ei.e.\u003c/em\u003e 5 less days, a 28% reduction) [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Our findings are also consistent with a recent study in pediatric URIs by Bettocchi et al., in which a probiotic mixture shortened the duration of fever from 5 days in the placebo group to 3 days in the treatment group, \u003cem\u003ei.e.\u003c/em\u003e a 40% decrease [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Interestingly, the absolute reduction of the duration of symptoms seems to change depending on the natural duration of the URI, yet the percent of reduction seems more comparable across studies with probiotics. This shortening of symptoms is noteworthy as antipyretics do not seem to reduce the overall duration of the disease [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], suggesting specific probiotics could be an interesting add-on to current treatments for URIs.\u003c/p\u003e\u003cp\u003e\u003cem\u003eLactiplantibacillus plantarum\u003c/em\u003e (formerly \u003cem\u003eLactobacillus plantarum\u003c/em\u003e) and closely related Lactobacillaceae bacteria such as Pediococci, are common endophytes, living in wild vegetables and frequently ingested by herbivores and omnivores [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. As such, the immune systems of the latter evolved under repeated intestinal exposure to the former, regardless of said bacteria behaving as nomadic commensals or successfully engrafting in the intestine (\u003cem\u003ei.e.\u003c/em\u003e becoming autochthonous). A seminal randomized trial in more than 4,000 newborns, comparing \u003cem\u003eL. plantarum\u003c/em\u003e strain ATCC202195 to placebo, found a significant reduction in lower respiratory tract infections and sepsis [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The formula used in the current study, containing \u003cem\u003eL. plantarum\u003c/em\u003e (strains KABP022, KABP023 and KABP033) and \u003cem\u003eP. acidilactici\u003c/em\u003e (strain KABP021), was previously tested in a randomized clinical trial in 300 adults with PCR-confirmed, symptomatic Covid19, resulting in reduced duration of symptoms and viral load [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. However, as the study population ranged 18 to 60 years old, evidence was missing in pediatric patients. Besides, \u003cem\u003ein vitro\u003c/em\u003e studies found this same probiotic formula induced type-I interferon response in phagocytic cells [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Noteworthy, gut microbiota modulation of the host\u0026rsquo;s tonic type-I interferons seems to mediate systemic antiviral effects in mouse models [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. In our study, a reduction in the incidence of nasal congestion and in the total number of symptoms per patient was also observed at two weeks, but not six weeks, after completing the 15-day intervention (\u003cem\u003ei.e.\u003c/em\u003e 30 days but not 60 days from baseline). Thus, immune-stimulating effects were seemingly maintained for a limited time once probiotic ingestion stopped, a finding deserving further investigations.\u003c/p\u003e\u003cp\u003ePrevious randomized trials of probiotics for URIs in children have mostly relied on parent/caregiver diagnosis [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. This introduces a potential confounder, every patient in the study being diagnosed by a different, untrained person. In this regard, a recent large trial found no effect of \u003cem\u003eL. rhamnosus\u003c/em\u003e DSM33153 (\u003cem\u003ea.k.a.\u003c/em\u003e ATCC53103) on URIs diagnosed by a physician and confirmed by laboratory tests [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], despite the same strain showing positive effects in previous trials that relied on parental diagnosis and did not identify etiologic agent [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Therefore, proper diagnosis by a physician and use of molecular methods seems relevant to increase the reliability of such clinical trials. Conversely, other recent probiotic studies relying on diagnosis by specialists alone [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] or specialist and molecular methods [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] found a significant effect against URIs, using different strains [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. This apparent disparity may be explained by the fact that probiotic effects are often strain-specific, particularly immune-effects, and should not be extrapolated one strain to another [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. In this regard, URI in our study were diagnosed by pediatricians based on clear clinical criteria (pharyngitis accompanied by fever) and confirmed by molecular method, thereby enhancing the robustness of our findings.\u003c/p\u003e\u003cp\u003eNo single causative agent dominated our study population. Rhinovirus (36.0%), coronaviruses (28.0%, two thirds being SARS-CoV2) and RSV (25.3%) were the most prevalent, in line with recent studies [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Human metapneumovirus (14.6%) and adenoviruses (10.7%) were moderately prevalent, while influenza, parainfluenza and human bocavirus had a prevalence\u0026thinsp;\u0026lt;\u0026thinsp;10% each. A recent study in children found infections with rhinovirus, RSV or metapneumovirus resulted in higher severity and/or a risk of hospitalization, underscoring the importance of effective therapies for these viruses [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Of note, causative agents are seldom reported in URI trials with probiotics [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], yet their diversity introduces a potential confounder, unless properly accounted for: as the number of causative agents increases, so do the chances of a random imbalance between study groups (especially in moderately sized studies). Moreover, having several infectious agents in the same study entails the possibility of high efficacy against some viruses to mask low efficacy against others. Therefore, sensitivity analyses seem desirable to rule out such confounders. In this regard, our study is a first in probiotic research for URIs, to our knowledge.\u003c/p\u003e\u003cp\u003eAll adverse events (AEs) in the study were mild and of gastrointestinal (GI) type. Previous studies have noted that GI symptoms are common among URI patients [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. In our study, several patients reported GI symptoms already at baseline. Unfortunately, such baseline info was not collected in a systematic, solicited manner, thus preventing a proper analysis of treatment-emergent AEs for all patients. Nevertheless, AE incidence did not differ between study groups, suggesting the probiotic intervention was well-tolerated.\u003c/p\u003e\u003cp\u003eSeveral study limitations should be pointed out. First, several URI symptoms were rated as present/absent (instead of a severity scale), and were not required as entry criteria, thus reducing our capacity to detect differences between groups. A better assessment of these secondary endpoints could have been obtained with a more precise symptoms scale, such as the WURSS. However, the pediatric version of this scale has only been validated for children 4 years and older [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Second, a causative virus could not be identified in 10 patients (13.3%) despite using a large panel identifying up to 19 viruses. These cases could be false negatives, viruses not in our panel and/or bacterial infections resembling viral infections, yet they were fairly balanced between study groups. Third, the prevalence of common viruses such as influenza or adenoviruses was low in our population. Nevertheless, most prevalent viruses in our population coincided with a recent meta-analysis [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], and sensitivity analyses indicated efficacy in our study was not dependent on these prevalent viruses. Fourth, recording of highest daily temperature is affected by timing of the measurement, while FLACC score measures both pain and distress or discomfort [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] and is dependent on subjective assessment. However, the concurrent effect in both co-primary endpoints, below the multiplicity-adjusted threshold of p\u0026thinsp;=\u0026thinsp;0.025, helps strengthen our conclusions. Moreover, days of use of ibuprofen markedly correlated with both endpoints, adding internal validity. Finally, no fecal microbiota analysis was included in our study. However, the previous randomized trial with the same probiotic found significant clinical effects despite no significant taxonomical changes in fecal microbiota [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], akin to other publications [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn conclusion, our study suggests the specific probiotic formula containing strains \u003cem\u003eP. acidilactici\u003c/em\u003e KABP021 and \u003cem\u003eL. plantarum\u003c/em\u003e KABP022, KABP023 and KABP033 helps shorten the duration of fever and pain/discomfort in children with URI with pharyngitis of diverse viral origin. This formula may also reduce the severity of relapses or new infections for a limited time after completing the intervention. Said results warrant replication in larger, multi-centric, randomized trials.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eAE Adverse Event; AUC Area Under the Curve; CFU Colony-Forming units; CONSORT Consolidated Standards of Reporting Trials; FLACC Face, Legs, Activity, Crying and Consolability; GLM Generalized Linear Model; RSV Respiratory Syncytial Virus; SPSS Statistical Package for the Social Sciences; URI Upper Respiratory Infection.\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eThis work was fully sponsored by AB-Biotics, S.A (Kaneka Corp.).\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003cp\u003eJE-M, JVC and MR-P are full-time employees of AB-Biotics SA (Kaneka Group), the company that funded the study. DA-P and MGM-F declare no competing interests for this work.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003ch2\u003eEthics approval:\u003c/h2\u003e\u003cp\u003e The study was conducted in accordance with the Declaration of Helsinki, and approval was obtained from Hospital Medica Sur research ethics boards.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConsent to participate:\u003c/strong\u003e\u003cp\u003e Parents of all participants provided written informed consent.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eDA-P, JE-M and MR-P conceptualized and designed the study. DA-P and MGM-F recruited and treated patients, and collected data. JE-M analyzed the data. JE-M and JVC drafted the initial manuscript. DA-P and MR-P critically reviewed the manuscript. All authors approved the final manuscript as submitted.\u003c/p\u003e\u003ch2\u003eData availability:\u003c/h2\u003e\u003cp\u003eAll data used in the current publication are available (duly anonymized) from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eSirota SB, Doxey MC, Dominguez R-MV, Bender RG, Vongpradith A, Albertson SB, Novotney A, Burkart K, et al (2024) Global, regional, and national burden of upper respiratory infections and otitis media, 1990\u0026ndash;2021: a systematic analysis from the Global Burden of Disease Study 2021. Lancet Infect Dis. https://doi.org/10.1016/S1473-3099(24)00430-4\u003c/li\u003e\n\u003cli\u003eLaurent GJ, Shapiro SD (2006) Encyclopedia of Respiratory Medicine, 1st ed. 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J Med Virol 94:6103\u0026ndash;6110. https://doi.org/10.1002/JMV.28031\u003c/li\u003e\n\u003cli\u003eMinodier L, Masse S, Capai L, Blanchon T, Ceccaldi PE, van der Werf S, Hanslik T, Charrel R, et al (2017) Clinical and virological factors associated with gastrointestinal symptoms in patients with acute respiratory infection: a two-year prospective study in general practice medicine. BMC Infect Dis 17:. https://doi.org/10.1186/S12879-017-2823-9\u003c/li\u003e\n\u003cli\u003eNewman KL, Wolf CR, Logue JK, Englund JA, Boeckh M, Chu HY (2023) Nausea, Vomiting, and Diarrhea Are Common in Community-Acquired Acute Viral Respiratory Illness. Dig Dis Sci 68:3383\u0026ndash;3389. https://doi.org/10.1007/S10620-023-07976-4\u003c/li\u003e\n\u003cli\u003eSchmit KM, Brown R, Hayer S, Checovich MM, Gern JE, Wald ER, Barrett B (2021) Wisconsin Upper Respiratory Symptom Survey for Kids: Validation of an Illness-specific Quality of Life Instrument. Pediatr Res 90:1207\u0026ndash;1214. https://doi.org/10.1038/S41390-021-01395-9\u003c/li\u003e\n\u003cli\u003eBabl FE, Crellin D, Cheng J, Sullivan TP, O\u0026rsquo;Sullivan R, Hutchinson A (2012) The use of the faces, legs, activity, cry and consolability scale to assess procedural pain and distress in young children. Pediatr Emerg Care 28:1281\u0026ndash;1286. https://doi.org/10.1097/PEC.0B013E3182767D66\u003c/li\u003e\n\u003cli\u003eWie\u0026euml;rs G, Belkhir L, Enaud R, Leclercq S, Foy J-MP de, Dequenne I, Timary P de, Cani PD (2019) How Probiotics Affect the Microbiota. Front Cell Infect Microbiol 9:454. https://doi.org/10.3389/FCIMB.2019.00454\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-pediatrics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejpe","sideBox":"Learn more about [European Journal of Pediatrics](https://www.springer.com/journal/431)","snPcode":"431","submissionUrl":"https://submission.nature.com/new-submission/431/3","title":"European Journal of Pediatrics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Upper respiratory infection, virus, probiotic, Lactiplantibacillus plantarum, Pediococcus acidilactici","lastPublishedDoi":"10.21203/rs.3.rs-7214019/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7214019/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eUpper respiratory infections (URIs) are highly prevalent, especially among young children. We aimed to investigate the efficacy and safety of a specific probiotic formula in shortening the duration of pediatric URIs of viral origin.\u003c/p\u003e\n\u003cp\u003eA randomized, double-blind clinical trial was conducted in children aged 6 months to 5 years, with URI with pharyngitis as diagnosed by a specialist. Participants were allocated to probiotic (strains \u003cem\u003eL. plantarum\u003c/em\u003e KABP022, KABP023 and KABP033, and \u003cem\u003eP. acidilactici\u003c/em\u003e KABP021) or placebo, twice daily for 15 days, and further followed up at 30 and 60 days from baseline. Antipyretic (ibuprofen) and antihistamine (cetirizine) were allowed as comedication and controlled. Co-primary outcomes were days of fever (axillary temperature \u0026gt;37.5ºC) and days of pain/discomfort (Face, Legs, Activity, Cry and Consolability [FLACC] score \u0026gt;3), as recorded in a diary. Causative viruses were identified by PCR in nasopharyngeal swabs.\u003c/p\u003e\n\u003cp\u003e75 children were randomized and included in the analysis. Most frequent causative agents were rhinoviruses, coronaviruses and respiratory syncytial virus. Compared to placebo, duration of fever and of pain/discomfort were reduced by 1.1 days (95%CI 0.5-1.7; p=0.001), and by 0.7 days (95%CI 0.2-1.2; p=0.006) in probiotic group, respectively. Sensitivity analyses by detected virus, age, sex and recent URI episodes produced similar results. Use of comedication and other symptoms did not differ between study groups. No significant differences were found in the number of adverse events between the groups.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e Intervention with this probiotic formula was associated with shorter duration of fever and pain/discomfort in pediatric URIs with pharyngitis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTrial Registration:\u003c/strong\u003e Prospectively registered on Oct 5\u003csup\u003eth\u003c/sup\u003e, 2023, as ISRCTN-66122782.\u003c/p\u003e","manuscriptTitle":"A Probiotic Containing L. Plantarum and P. Acidilactici Strains for Treating Upper Respiratory Infection in Children Aged 6 Months to 5 Years: A Randomized, Double-Blind Trial","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-04 08:11:47","doi":"10.21203/rs.3.rs-7214019/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-09-09T18:52:07+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-08T19:47:34+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"192758766667857347644504719077331570812","date":"2025-08-04T10:48:19+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-03T17:29:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"151487501750077424958618227102422206507","date":"2025-07-28T14:32:59+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-28T14:01:47+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-28T00:47:32+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-28T00:26:28+00:00","index":"","fulltext":""},{"type":"submitted","content":"European Journal of Pediatrics","date":"2025-07-25T11:39:59+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-pediatrics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejpe","sideBox":"Learn more about [European Journal of Pediatrics](https://www.springer.com/journal/431)","snPcode":"431","submissionUrl":"https://submission.nature.com/new-submission/431/3","title":"European Journal of Pediatrics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"9285a31f-3886-4a18-b40b-761cd88ecca8","owner":[],"postedDate":"August 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-01T16:13:00+00:00","versionOfRecord":{"articleIdentity":"rs-7214019","link":"https://doi.org/10.1007/s00431-025-06587-7","journal":{"identity":"european-journal-of-pediatrics","isVorOnly":false,"title":"European Journal of Pediatrics"},"publishedOn":"2025-11-26 15:58:06","publishedOnDateReadable":"November 26th, 2025"},"versionCreatedAt":"2025-08-04 08:11:47","video":"","vorDoi":"10.1007/s00431-025-06587-7","vorDoiUrl":"https://doi.org/10.1007/s00431-025-06587-7","workflowStages":[]},"version":"v1","identity":"rs-7214019","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7214019","identity":"rs-7214019","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}