Correlation between Pertussis Toxin IgG and Severity of Pertussis in Unvaccinated Chinese infant patients with acute pertussis

Correlation between Pertussis Toxin IgG and Severity of Pertussis in Unvaccinated Chinese infant patients with acute pertussis | 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 Article Correlation between Pertussis Toxin IgG and Severity of Pertussis in Unvaccinated Chinese infant patients with acute pertussis Chuan Gan, Gaihuan Zheng This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4789734/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background： Vaccination-induced PT-IgG offers protective effects against pertussis, and there is an inverse correlation between antibody levels and disease severity. However, there is limited research exploring the relationship between PT-IgG levels and disease severity in unvaccinated children with acute pertussis. Method： This study collected data from 302 unvaccinated children with acute pertussis. The aim was to investigate the relationship between disease-induced PT-IgG levels and the severity of pertussis. Result： 302 patients were divided into four groups based on their antibody levels. Most patients (83.77%) had antibody levels below 50.00IU/ml, while a smaller portion (16.23%) had levels above 50.00IU/ml. The length of hospital stay decreased significantly as antibody levels increased (P=0.044). Similar trends were observed for the highest WBC and Lymphocyte count during infection; and these differences were statistically significant (P<0.001 for both). There were no significant differences in the highest heart rate and respiratory rate among the patients (P=0.379 and P=0.963, respectively);Complication, including pneumonia, severe pneumonia, and respiratory failure, also showed no significant differences among the groups (P=0.400, P=0.158, and P=0.131, respectively).Raised C-reactive protein and raised Procalcitonin levels did not differ significantly between the groups (P=0.285 and P=0.170, respectively). Additionally, there were no significant differences in bacterial or viral co-infection rates among the groups (P=0.698 and P=0.623, respectively). Conclusion： In Chinese infant patients with acute pertussis who have not received vaccination, the PT-IgG levels are predominantly below 50.00IU/ml. Despite the protective role of PT-IgG, higher antibody levels do not appear to significantly reduce the severity. Health sciences/Diseases/Infectious diseases/Bacterial infection Biological sciences/Immunology/Antimicrobial responses Biological sciences/Immunology/Applied immunology Biological sciences/Immunology/Infectious diseases Pertussis PT-IgG Unvaccinated Infant Acute 1.Introduction Pertussis, a respiratory infectious disease preventable by vaccination, remains a threat to human health, particularly in children. Widespread vaccination against pertussis has led to a decline in incidence and mortality rates, attributable to the protective effects of PT-IgG following vaccination [ 1 – 2 ] .Serum IgG against pertussis toxin (PT) can be induced by either disease or vaccination. The induction of anti-PT IgG by immunization is mainly due to PT being a component of the acellular pertussis vaccine [ 3 ] .Following infection with Bordetella pertussis, the human body produces a large amount of toxins, such as Pertactin (PRN), Fimbriae (FIM), and Pertussis Toxin (PT). These toxins can also induce the production of corresponding antibodies in the body, among which PT-IgG is a specific antibody against Bordetella pertussis [ 4 ] .Many studies have focused on the value of PT-IgG in protecting the body after immunization, acknowledging its role in preventing the occurrence and progression of disease following vaccination [ 1 , 5 – 6 ] .For unvaccinated patient, PT-IgG is primarily produced following an infection with Bordetella pertussis.A few studies suggest that serum IgG against pertussis toxin (PT), whether induced by disease or vaccination, is both essential and sufficient for immunity to pertussis [ 2 ] .Currently, there are no dedicated studies on the relationship between PT-IgG levels during the acute phase of Bordetella pertussis infection and disease severity in unvaccinated individuals. Therefore, we collected clinical data from 302 unvaccinated acute-phase pertussis patients and tested their PT-IgG levels to investigate the correlation between naturally induced PT-IgG levels and the severity of pertussis in unvaccinated Chinese children. 2.Materials and Methods 2.1 Patient Selection A total of 302 patients under one year of age, diagnosed with pertussis from April 1, 2018 to July 31, 2019 at the Children's Hospital of Chongqing Medical University, were enrolled in this study.Pertussis diagnosis was established based on clinical signs and confirmed via PCR testing, with all patients undergoing PT-IgG testing.Anti-PT IgG was detected using the commercially available ELISA kits (Zhengzhou Yite, China), according to the manufacturer’s instructions.The antibody results were expressed in international units per mini-liter (IU/ml) .PT-IgG Test should be conducted within three weeks from the onset of cough.Patients with severe heart, lung diseases, or other serious underlying conditions were excluded from the study.The patients were categorized into four groups according to their PT-IgG: those with a PT-IgG count of 0.00 IU/ml-5.00 IU/ml were placed in Group A, those with a PT-IgG count between 5.01 IU/ml and 50.00 IU/ml were placed in Group B, those with a PT-IgG count between 50.01 IU/ml and 100.00 IU/ml were placed in Group C, and those with a PT-IgG count of 100.01 IU/ml or more were placed in Group D. Clinical data for each patient, including gender, age of onset, hospital length of stay, highest heart rate (beats/min), highest respiratory rate (breaths/min), complications, C-reactive protein, procalcitonin, co-infection, and results of peripheral blood cell analysis, were collected using big data platforms and electronic medical record systems. 2.2 Variables Recorded and Definitions Pneumonia was diagnosed according to the radiologists’ report based on pulmonary infiltrates or opacities. Severe pneumonia is defined as pneumonia with the occurrence of respiratory failure; Respiratory failure is defined by the presence of clinical manifestations of hypoxia and increased breathing rate(60/ min);pulmonary hypertension is indicated by an echocardiogram showing increased pulmonary artery pressure; Pulmonary consolidation is indicated by imaging studies showing consolidative changes; The diagnostic criteria for cardiovascular failure was as follows: increased heart rate (160/min) and echocardiogram suggesting abnormal cardiac function; Bacterial co-infection is defined as a positive sputum culture and the detection of the relevant bacteria. Viral co-infection is defined as a positive respiratory pathogen antigen test. Raised C-reactive protein is defined as C-reactive protein levels exceeding 8 mg/L; raised procalcitonin is defined as procalcitonin levels exceeding 0.05 ng/ml. 2.3 Statistical Analysis Statistical analyses were performed using SPSS software version 25. Descriptive analyses for non-normally distributed data are presented using the median (interquartile range). Comparisons between two groups were calculated using the Mann-Whitney test, and multigroup comparisons were conducted using the Kruskal-Wallis rank test. Count data are expressed as rates (%), and differences between groups were calculated using the chi-square test. Receiver operating characteristic curve (ROC) analyses and sensitivity and specificity values were calculated using MedCalc version 14. A P-value < 0.05 was considered statistically significant. 3.Result 3.1 Antibody Level Grouping and General Information A total of 302 patients were enrolled in the study and divided into four groups based on their antibody levels(see in Table 1 ): Group A with antibody levels from 0.00IU/ml to 5.00IU/ml, consisting of 167 patients; Group B with antibody levels from 5.01IU/ml to 50.00IU/ml, comprising 86 patients; Group C with antibody levels from 50.01IU/ml to 100.00IU/ml, including 24 patients; and Group D with antibody levels exceeding 100IU/ml, made up of 25 patients. The proportions of patients in these groups were 55.30%, 28.47%, 7.95%, and 8.28%, respectively.The majority (83.77%) had antibody levels below 50.00, with a smaller portion (16.23%) above 50.00. The study included 130 female participants, with female making up 43.05% of the sample; within the four patient groups, females were less represented than males in groups A, B and D, while group C had more females than males. However, there was no significant difference in gender distribution among the groups (P = 0.437).The onset ages of the 302 patients ranged from a minimum of 13 days to a maximum of 353 days. The onset ages for the four patient groups were respectively 79 (55, 112), 71 (43, 123.5), 63 (39.8, 131.3), and 86 (61, 138) days. There was no statistically significant difference in the onset ages among the groups༈P = 0.574༉.The length of hospital stay for the four patient groups was respectively 8 (6, 12), 7 (5, 10), 7.5 (5, 9.8), and 6 (5, 10) days. We observed that as antibody levels increased, the length of hospital stay decreased. The length of hospital stay for the four patient groups was significantly shorter as antibody levels increased (P = 0.044). Clinical indicators such as the highest heart rate and the highest respiratory rate showed no significant differences among the patients (P = 0.379 and P = 0.963, respectively). Table 1 . Table 1 Distribution of Patients Based on PT-IgG Levels and General Information Group Group A Group B Group C Group D Statistical Value p value 167(55.30%) 86(28.47%) 24(7.95%) 25(8.28%) Gender(female,n,%) 44.91% 38.40% 54.16% 36% 2.72 0.437 Age of onset (day), median (IQR) 79(55,112) 71(43,123.5) 63(39.8,131.3) 86(61,138) 1.991 0.574 Hospital length of stay, median (IQR) 8(6,12) 7(5,10) 7.5(5,9.8) 6(5,10) 8.074 0.044 Highest heart rate(beats/min) 130(125,136) 130(122,136) 130(124,135) 130(122,135) 3.085 0.379 Highest respiratory rate(breaths/min) 42(36,52) 41(38,46) 42(34,46) 42(34.5,47.5) 0.285 0.963 3.2 Peripheral Blood Cells and Inflammatory Markers Peripheral blood cell count is the simplest and most commonly used indicator for detecting pertussis in patients. We know that elevated WBC counts and lymphocytosis are common phenomena in patients with pertussis, and an abnormally elevated white blood cell count is an important indicator of the severity of a disease. Therefore, peripheral blood cell counts are typically used as indicators of disease severity, especially for highest WBC count and highest lymphocyte counts. In our study,The peripheral blood cell counts in the four patient groups showed highest WBC counts with medians (IQR) respectively as follows: 16.73(12.54,24.99), 14.73(11.24,21.95), 12.83(10.2,17.60), 12.14(9.07,15.75). As antibody levels increased, the highest WBC count gradually decreased, showing a significant difference (P < 0.001). The highest lymphocyte counts were 12.48(8.28,17.79), 10.17(7.66,16.65), 8.51(5.60,12.39), 8.04(5.77,10.41), respectively, also demonstrating a gradual decrease with significant differences (P < 0.001). reactive protein and procalcitonin are important indicators of the inflammatory state. In our study, only 16 cases showed an increase in C-reactive protein, accounting for a low proportion of 5.29% (16/302). The rates of Raised C-reactive protein among the four patient groups were 5.4%, 4.7%, 12.5%, and 0.0%, respectively, with no statistically significant difference (P = 0.285). Raised procalcitonin was more common, observed in a total of 194 cases, representing 64.24% (194/302). The rates of increased procalcitonin among the four patient groups were 67.1%, 61.6%, 45.8%, and 72.0%, respectively, with no statistically significant difference (P = 0.170). Table 2 . Table 2 Comparison of peripheral blood cell and inflammatory marker results at different antibody level . Pertussis Toxin IgG antibodies Group A Group B Group C Group D Statistical Value p value N = 167 N = 86 N = 24 N = 25 WBC count, highest cells×10 3 /µL, median (IQR) 16.73 (12.54,24.99) 14.73 (11.24,21.95) 12.83 (10.2,17.60) 12.14 (9.07,15.75) 18.312 <0.001 Lymphocyte count, highest cells×10 3 /µL, median (IQR) 12.48 (8.28,17.79) 10.17 (7.66,16.65) 8.51 (5.60,12.39) 8.04 (5.77,10.41) 22.363 <0.001 Raised C-reactive protein (n,%) 9(5.4%) 4(4.7%) 3(12.5%) 0(0.0%) 3.341 0.285 Raised Procalcitonin(n,%) 112(67.1%) 53(61.6%) 11(45.8%) 18(72.0%) 5.031 0.170 3.3 Complications Complications are common indicators of the severity of a disease, including pneumonia, severe pneumonia, respiratory failure, heart failure, and neurological complications. In our study, pneumonia was the most common complication, occurring in 233 out of 302 patients, accounting for 77.15% (233/302), indicating that pneumonia is the most frequent complication among unvaccinated infants with pertussis. The incidence of complications among the four patient groups is presented in Table 3 . Pneumonia was most common in all four groups, with percentages of 79.0%, 70.9%, 79.2%, and 84%, respectively, and the differences were not statistically significant (P = 0.158). Compared to the high incidence of pneumonia, severe pneumonia occurred in only 29 cases, accounting for 9.60% (29/302), significantly lower than the incidence rate of pneumonia (77.15%). Severe pneumonia was observed in four groups, with percentages of 9.6%, 14.0%, 4.2%, and 0.0%, and the differences were not statistically significant (P = 0.158). The incidence rate of respiratory failure was essentially the same as that of severe pneumonia. Respiratory failure rates were observed in four groups, with percentages of 8.4%, 14.0%, 4.2%, and 0.0%, and differences also were not statistically significant (P = 0.131). Complications outside the respiratory system were mainly Cardiovascular failure and neurological complications. In our study, the incidence rates of these two types of complications were extremely low, with only one case occurring for each.Table 3 . Table 3 Patient Complications Complication Group A Group B Group C Group D Statistical Value p value N = 167 N = 86 N = 24 N = 25 Pneumonia(n,%) 132(79.0%) 61(70.9%) 19(79.2%) 21(84%) 2.947 0.400 Severe Pneumonia(n,%) 16(9.6%) 12(14.0%) 1(4.2%) 0(0.0%) 4.847 0.158 Respiratory failure(n,%) 14(8.4%) 12(14.0%) 1(4.2%) 0(0.0%) 5.126 0.131 Cardiovascular failure(n,%) 0(0.0%) 1(1.2%) 0(0.0%) 0(0.0%) / / Seizure(n,%) 0(0.0%) 0(0.0%) 1(4.2%) 0(0.0%) / / 3.4 Co-infections Co-infection is a common phenomenon among patients with pertussis, especially co-infection with bacterial or viral infections. In our study, bacterial co-infection rates were most common in all four groups, with percentages of 46.1%, 38.4%, 45.8%, and 44.0%, respectively, and showed a non-significant trend (P = 0.698). However, the rates of bacterial co-infection among the four patient groups did not decrease with increasing antibody levels, showing no significant difference. This phenomenon was also observed in the incidence of viral co-infections, with rates common in all four groups, with percentages of 22.8%, 30.2%, 25.0%, and 28.0%, respectively, and showed a non-significant trend (P = 0.623). These results suggest that the level of antibodies does not affect the occurrence of bacterial or viral co-infections.Table 4 Table 4 co-infection with bacterial or viral Co-infection Group A Group B Group C Group D Statistical Value p value N = 167 N = 86 N = 24 N = 25 bacterial coinfection(n,%) 77(46.1%) 33(38.4%) 11(45.8%) 11(44.0%) 1.431 0.698 viral coinfection(n,%) 38(22.8%) 26(30.2%) 6(25.0%) 7(28.0%) 1.762 0.623 4. Discussion Pertussis remains a significant public health concern, particularly in regions with lower vaccination rates. Vaccination serves as an effective preventive strategy, fundamentally because it stimulates the production of anti-PT IgG antibodies, which are crucial for protecting against pertussis [ 7 – 8 ] .Following widespread vaccination, the incidence and mortality rates have greatly improved. However, numerous children remain unvaccinated against pertussis due to varying local policies on the minimum age for vaccination, being below the recommended age, illness, and other family-related factors.Those who have not been vaccinated face a higher risk of infection when exposed to pertussis compared to those who have received the vaccine. The severity of the disease is also greater after infection.The primary reason is that persons who lack PT IgG are susceptible to pertussis [ 5 – 6 ] . Among the 302 enrolled Chinese pediatric patients who were not vaccinated, 55.30% of the children had antibody levels of 5.00IU/ml or below, while 83.77% of the patients had antibody levels of 50.00IU/ml or below. Only 16.23% had antibody levels exceeding 50.00IU/ml. This suggests that the acute-phase antibody levels among Chinese children with pertussis who are not vaccinated are generally low.This phenomenon is considered to possibly relate to the generally low antibody levels among the population in our country. Research by Qing-Hong Meng et al. indicates that newborns in Beijing generally lack protective antibodies and are vulnerable to pertussis, with 66.5% of newborns having PT-IgG levels below 5IU/ml [ 9 ] .Zhiyun Chen et.al research indicates that the geometric mean concentration (GMC) and median concentration of anti-PT IgG antibodies were 1.72 IU/mL and 1.43 IU/mL among infants under 3 months of age [ 10 ] .Additionally, there is also a low seropositivity rate for anti-PT IgG, particularly among school-aged children [ 11 ] . Studies indicating that the risk of mortality in severe pertussis, particularly among females, is higher than in males [ 12 ] .In our study, males predominated, with only 130 female participants. There was no significant difference between females and males across the groups (P = 0.437). This may be considered in the context that all patients in our study were from general wards and there were no fatal cases. Previous studies have shown that the severity and mortality rates among females are higher than in males, primarily within the group of severe pertussis patients. Elevated WBC counts and lymphocytosis are common phenomena in patients with pertussis, and significant leukocytosis (Hyperleukocytosis) is a risk factor for death in patients with pertussis [ 13 ] .PT is a central factor driving the pathogenesis of pertussis. It is also considered to be the main cause of leukocytosis [ 14 – 15 ] .However,serum IgG against PT, whether induced by disease or vaccination, was both essential and sufficient for immunity to pertussis [ 2 ] .In our study, we found that the highest WBC count and highest lymphocyte count decreased with increasing antibody levels, and the differences were significant (P < 0.001; P < 0.001). This suggests that higher antibody levels are associated with lower peak values of WBC and lymphocytes, indicating that higher antibody levels may be linked to a lower severity of the disease.In our study, however, we did not observe this phenomenon clinically. We found no significant differences in the highest heart rate and highest respiratory rate among patients (P = 0.379, 0.963), and a similar situation was observed with complications. The incidence rates of pneumonia, severe pneumonia, and respiratory failure were also not significantly different among the groups (P = 0.400, 0.158, 0.131). C-reactive protein and procalcitonin are important indicators of the inflammatory state, especially when the body is in an infectious state. In our study, the rate of Raised C-reactive protein was extremely low, and there was no significant relationship between it and antibody levels. Not only for C-reactive protein, but we also found no significant relationship between the rate of Raised procalcitonin and antibody levels. The study found that compared with simple pertussis infection, the clinical symptoms after co-infection were more severe [ 16 ] , in our study, there was no significant difference in the rate of bacterial or viral co-infection among the four groups of patients, suggesting that the level of antibodies had no significant impact on the occurrence of co-infection, which also indirectly indicates that there is no significant relationship between antibody levels and disease severity. In our study, significant differences were observed in hospital length of stay, highest WBC count, and highest lymphocyte counts, but the incidence rates of clinical complications (pneumonia, severe pneumonia, respiratory failure), the rates of elevated inflammatory markers, and the rates of concurrent bacterial or viral infections showed no significant differences. It is currently believed that the production of a large number of anti-PT IgG antibodies after vaccination or infection should provide sufficient protection [ 17 – 18 ] . However, the neutralizing power of antibodies is overlooked, and it is also believed that high antibody concentrations do not always guarantee good neutralizing ability [ 19 – 20 ] . This seems to explain the phenomenon observed in our study: the level of antibodies did not affect the clinical severity of the disease. It is hypothesized that pertussis antibodies may not play as significant a role in protecting against ordinary rather than severe cases of pertussis. This also reminds us that clinicians should not solely rely on the level of antibodies to predict the severity or prognosis of a patient's disease. In this study, we observed that in unvaccinated pediatric patients with acute-phase pertussis, higher PT-IgG levels are associated with shorter hospital stays, lower WBC counts, and lower lymphocyte counts, indicating an attenuated inflammatory response. However, the PT-IgG levels did not significantly impact the severity of complications, elevation of inflammatory markers, or incidence of coinfections, suggesting that while higher antibody levels can reduce inflammation, they do not necessarily mitigate the overall severity of the disease. This study provides insights into the relationship between PT-IgG levels and pertussis severity in unvaccinated Chinese children. Despite the protective role of PT-IgG, higher antibody levels do not appear to significantly reduce the severity, highlighting the importance of vaccination to prevent the disease rather than relying on natural antibody production post-infection. Further research is needed to fully understand the immunological mechanisms and the potential benefits of higher PT-IgG levels in the management of pertussis. Declarations Funding Declaration : No funding Author Contribution Author (first author): Chuan Gan Contributions: WParticipate in the treatment of patient, acquired, analyzed and interpreted the data and draft the manuscript. Author (corresponding author): Gaihuan ZhengContributions: Revised the important intellectual content in the article; and approved the final submitted version Data Availability All data included in this study are available upon request by contact with the corresponding author References Taranger J, Trollfors B, Lagergård T, Sundh V, Bryla DA, Schneerson R, et al. Correlation between pertussis toxin IgG antibodies in postvaccination sera and subsequent protection against pertussis. J Infect Dis. 2000;181(3):1010–3. doi: 10.1086/315318 . 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Toxins (Basel). 2021;13(8):508. doi: 10.3390/toxins13080508 . Zhang Y., Li Y., Chen Z., Liu X., Peng X., He Q. Determination of serum neutralizing antibodies reveals important difference in quality of antibodies against pertussis toxin in children after infection. Vaccine. 2021;39:1826–1830. doi: 10.1016/j.vaccine.2021.02.045 . Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. 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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-4789734","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":343692710,"identity":"5ba32b18-66c3-4d89-a35a-ad7a67976b21","order_by":0,"name":"Chuan Gan","email":"","orcid":"","institution":"The Infection Department of Children’s Hospital of Chongqing Medical University","correspondingAuthor":false,"prefix":"","firstName":"Chuan","middleName":"","lastName":"Gan","suffix":""},{"id":343692711,"identity":"f72d65f9-1267-4b72-affe-aa0b0989f850","order_by":1,"name":"Gaihuan Zheng","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1klEQVRIiWNgGAWjYFACxjYQycPP3nzgwIcfJGiRkew5lnhwZg9x1rCBCBuDGTnGhznYiFAv73647TFPzR0eA54zHw4z8DDI84sdwK/F8ExiuzHPsWc85uy9Gw4XWDAYzpydQEBLQ2KbNA/bYR7LnrMbDs/gYUgwuE1IS/9DoJZ/h3kMbuQ8OMzDRoQWeQmgLbxtYC0MxGkxkHjYJjm37zAPMJANgIEsQdgv8v3pzyTefDtsD4zKxx8+/LCR55cmZMsBVL4EfuVgWxoIqxkFo2AUjIKRDgAlskh196wnagAAAABJRU5ErkJggg==","orcid":"","institution":"The Infection Department of Children’s Hospital of Chongqing Medical University","correspondingAuthor":true,"prefix":"","firstName":"Gaihuan","middleName":"","lastName":"Zheng","suffix":""}],"badges":[],"createdAt":"2024-07-23 14:59:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4789734/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4789734/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":65189893,"identity":"ff1f3ef3-c88f-4e23-b052-bfef3a450100","added_by":"auto","created_at":"2024-09-24 14:24:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":510637,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4789734/v1/236eae7f-373f-41f7-adc9-9b8ab0ccf430.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Correlation between Pertussis Toxin IgG and Severity of Pertussis in Unvaccinated Chinese infant patients with acute pertussis","fulltext":[{"header":"1.Introduction","content":"\u003cp\u003ePertussis, a respiratory infectious disease preventable by vaccination, remains a threat to human health, particularly in children. Widespread vaccination against pertussis has led to a decline in incidence and mortality rates, attributable to the protective effects of PT-IgG following vaccination\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e.Serum IgG against pertussis toxin (PT) can be induced by either disease or vaccination. The induction of anti-PT IgG by immunization is mainly due to PT being a component of the acellular pertussis vaccine\u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e.Following infection with Bordetella pertussis, the human body produces a large amount of toxins, such as Pertactin (PRN), Fimbriae (FIM), and Pertussis Toxin (PT). These toxins can also induce the production of corresponding antibodies in the body, among which PT-IgG is a specific antibody against Bordetella pertussis\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e.Many studies have focused on the value of PT-IgG in protecting the body after immunization, acknowledging its role in preventing the occurrence and progression of disease following vaccination\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e.For unvaccinated patient, PT-IgG is primarily produced following an infection with Bordetella pertussis.A few studies suggest that serum IgG against pertussis toxin (PT), whether induced by disease or vaccination, is both essential and sufficient for immunity to pertussis\u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e.Currently, there are no dedicated studies on the relationship between PT-IgG levels during the acute phase of Bordetella pertussis infection and disease severity in unvaccinated individuals. Therefore, we collected clinical data from 302 unvaccinated acute-phase pertussis patients and tested their PT-IgG levels to investigate the correlation between naturally induced PT-IgG levels and the severity of pertussis in unvaccinated Chinese children.\u003c/p\u003e"},{"header":"2.Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Patient Selection\u003c/h2\u003e \u003cp\u003eA total of 302 patients under one year of age, diagnosed with pertussis from April 1, 2018 to July 31, 2019 at the Children's Hospital of Chongqing Medical University, were enrolled in this study.Pertussis diagnosis was established based on clinical signs and confirmed via PCR testing, with all patients undergoing PT-IgG testing.Anti-PT IgG was detected using the commercially available ELISA kits (Zhengzhou Yite, China), according to the manufacturer\u0026rsquo;s instructions.The antibody results were expressed in international units per mini-liter (IU/ml) .PT-IgG Test should be conducted within three weeks from the onset of cough.Patients with severe heart, lung diseases, or other serious underlying conditions were excluded from the study.The patients were categorized into four groups according to their PT-IgG: those with a PT-IgG count of 0.00 IU/ml-5.00 IU/ml were placed in Group A, those with a PT-IgG count between 5.01 IU/ml and 50.00 IU/ml were placed in Group B, those with a PT-IgG count between 50.01 IU/ml and 100.00 IU/ml were placed in Group C, and those with a PT-IgG count of 100.01 IU/ml or more were placed in Group D. Clinical data for each patient, including gender, age of onset, hospital length of stay, highest heart rate (beats/min), highest respiratory rate (breaths/min), complications, C-reactive protein, procalcitonin, co-infection, and results of peripheral blood cell analysis, were collected using big data platforms and electronic medical record systems.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Variables Recorded and Definitions\u003c/h2\u003e \u003cp\u003ePneumonia was diagnosed according to the radiologists\u0026rsquo; report based on pulmonary infiltrates or opacities. Severe pneumonia is defined as pneumonia with the occurrence of respiratory failure; Respiratory failure is defined by the presence of clinical manifestations of hypoxia and increased breathing rate(\u0026lt;\u0026thinsp;1 year: \u0026gt;60/ min);pulmonary hypertension is indicated by an echocardiogram showing increased pulmonary artery pressure; Pulmonary consolidation is indicated by imaging studies showing consolidative changes; The diagnostic criteria for cardiovascular failure was as follows: increased heart rate (\u0026lt;\u0026thinsp;1year: \u0026gt;160/min) and echocardiogram suggesting abnormal cardiac function; Bacterial co-infection is defined as a positive sputum culture and the detection of the relevant bacteria. Viral co-infection is defined as a positive respiratory pathogen antigen test. Raised C-reactive protein is defined as C-reactive protein levels exceeding 8 mg/L; raised procalcitonin is defined as procalcitonin levels exceeding 0.05 ng/ml.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Statistical Analysis\u003c/h2\u003e \u003cp\u003eStatistical analyses were performed using SPSS software version 25. Descriptive analyses for non-normally distributed data are presented using the median (interquartile range). Comparisons between two groups were calculated using the Mann-Whitney test, and multigroup comparisons were conducted using the Kruskal-Wallis rank test. Count data are expressed as rates (%), and differences between groups were calculated using the chi-square test. Receiver operating characteristic curve (ROC) analyses and sensitivity and specificity values were calculated using MedCalc version 14. A P-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"3.Result","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Antibody Level Grouping and General Information\u003c/h2\u003e \u003cp\u003eA total of 302 patients were enrolled in the study and divided into four groups based on their antibody levels(see in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e): Group A with antibody levels from 0.00IU/ml to 5.00IU/ml, consisting of 167 patients; Group B with antibody levels from 5.01IU/ml to 50.00IU/ml, comprising 86 patients; Group C with antibody levels from 50.01IU/ml to 100.00IU/ml, including 24 patients; and Group D with antibody levels exceeding 100IU/ml, made up of 25 patients. The proportions of patients in these groups were 55.30%, 28.47%, 7.95%, and 8.28%, respectively.The majority (83.77%) had antibody levels below 50.00, with a smaller portion (16.23%) above 50.00. The study included 130 female participants, with female making up 43.05% of the sample; within the four patient groups, females were less represented than males in groups A, B and D, while group C had more females than males. However, there was no significant difference in gender distribution among the groups (P\u0026thinsp;=\u0026thinsp;0.437).The onset ages of the 302 patients ranged from a minimum of 13 days to a maximum of 353 days. The onset ages for the four patient groups were respectively 79 (55, 112), 71 (43, 123.5), 63 (39.8, 131.3), and 86 (61, 138) days. There was no statistically significant difference in the onset ages among the groups༈P\u0026thinsp;=\u0026thinsp;0.574༉.The length of hospital stay for the four patient groups was respectively 8 (6, 12), 7 (5, 10), 7.5 (5, 9.8), and 6 (5, 10) days. We observed that as antibody levels increased, the length of hospital stay decreased. The length of hospital stay for the four patient groups was significantly shorter as antibody levels increased (P\u0026thinsp;=\u0026thinsp;0.044). Clinical indicators such as the highest heart rate and the highest respiratory rate showed no significant differences among the patients (P\u0026thinsp;=\u0026thinsp;0.379 and P\u0026thinsp;=\u0026thinsp;0.963, respectively). Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\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\u003eDistribution of Patients Based on PT-IgG Levels and General Information\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\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=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGroup A\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGroup B\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGroup C\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGroup D\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eStatistical Value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e167(55.30%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e86(28.47%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e24(7.95%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e25(8.28%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGender(female,n,%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e44.91%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e38.40%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e54.16%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e36%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.437\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge of onset (day), median (IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e79(55,112)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e71(43,123.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e63(39.8,131.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e86(61,138)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.991\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.574\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHospital length of stay, median (IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8(6,12)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7(5,10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.5(5,9.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6(5,10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e8.074\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.044\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHighest heart rate(beats/min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e130(125,136)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e130(122,136)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e130(124,135)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e130(122,135)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.085\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.379\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHighest respiratory rate(breaths/min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e42(36,52)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e41(38,46)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e42(34,46)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e42(34.5,47.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.285\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.963\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Peripheral Blood Cells and Inflammatory Markers\u003c/h2\u003e \u003cp\u003ePeripheral blood cell count is the simplest and most commonly used indicator for detecting pertussis in patients. We know that elevated WBC counts and lymphocytosis are common phenomena in patients with pertussis, and an abnormally elevated white blood cell count is an important indicator of the severity of a disease. Therefore, peripheral blood cell counts are typically used as indicators of disease severity, especially for highest WBC count and highest lymphocyte counts. In our study,The peripheral blood cell counts in the four patient groups showed highest WBC counts with medians (IQR) respectively as follows: 16.73(12.54,24.99), 14.73(11.24,21.95), 12.83(10.2,17.60), 12.14(9.07,15.75). As antibody levels increased, the highest WBC count gradually decreased, showing a significant difference (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The highest lymphocyte counts were 12.48(8.28,17.79), 10.17(7.66,16.65), 8.51(5.60,12.39), 8.04(5.77,10.41), respectively, also demonstrating a gradual decrease with significant differences (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003ereactive protein and procalcitonin are important indicators of the inflammatory state. In our study, only 16 cases showed an increase in C-reactive protein, accounting for a low proportion of 5.29% (16/302). The rates of Raised C-reactive protein among the four patient groups were 5.4%, 4.7%, 12.5%, and 0.0%, respectively, with no statistically significant difference (P\u0026thinsp;=\u0026thinsp;0.285). Raised procalcitonin was more common, observed in a total of 194 cases, representing 64.24% (194/302). The rates of increased procalcitonin among the four patient groups were 67.1%, 61.6%, 45.8%, and 72.0%, respectively, with no statistically significant difference (P\u0026thinsp;=\u0026thinsp;0.170). Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003c/li\u003e \u003c/ul\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\u003e\u003cb\u003eComparison of peripheral blood cell and inflammatory marker results at different antibody level\u003c/b\u003e .\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\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=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePertussis Toxin IgG antibodies\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGroup A\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGroup B\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGroup C\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGroup D\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eStatistical Value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;167\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;86\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;24\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;25\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWBC count, highest cells\u0026times;10\u003csup\u003e3\u003c/sup\u003e /\u0026micro;L, median (IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16.73\u003c/p\u003e \u003cp\u003e(12.54,24.99)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14.73\u003c/p\u003e \u003cp\u003e(11.24,21.95)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e12.83\u003c/p\u003e \u003cp\u003e(10.2,17.60)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12.14\u003c/p\u003e \u003cp\u003e(9.07,15.75)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e18.312\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLymphocyte count, highest\u003c/p\u003e \u003cp\u003ecells\u0026times;10\u003csup\u003e3\u003c/sup\u003e /\u0026micro;L, median (IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12.48\u003c/p\u003e \u003cp\u003e(8.28,17.79)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.17\u003c/p\u003e \u003cp\u003e(7.66,16.65)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.51\u003c/p\u003e \u003cp\u003e(5.60,12.39)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.04\u003c/p\u003e \u003cp\u003e(5.77,10.41)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e22.363\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRaised C-reactive protein (n,%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9(5.4%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4(4.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3(12.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0(0.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.341\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.285\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRaised Procalcitonin(n,%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e112(67.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e53(61.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11(45.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e18(72.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e5.031\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.170\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Complications\u003c/h2\u003e \u003cp\u003eComplications are common indicators of the severity of a disease, including pneumonia, severe pneumonia, respiratory failure, heart failure, and neurological complications. In our study, pneumonia was the most common complication, occurring in 233 out of 302 patients, accounting for 77.15% (233/302), indicating that pneumonia is the most frequent complication among unvaccinated infants with pertussis. The incidence of complications among the four patient groups is presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Pneumonia was most common in all four groups, with percentages of 79.0%, 70.9%, 79.2%, and 84%, respectively, and the differences were not statistically significant (P\u0026thinsp;=\u0026thinsp;0.158). Compared to the high incidence of pneumonia, severe pneumonia occurred in only 29 cases, accounting for 9.60% (29/302), significantly lower than the incidence rate of pneumonia (77.15%). Severe pneumonia was observed in four groups, with percentages of 9.6%, 14.0%, 4.2%, and 0.0%, and the differences were not statistically significant (P\u0026thinsp;=\u0026thinsp;0.158). The incidence rate of respiratory failure was essentially the same as that of severe pneumonia. Respiratory failure rates were observed in four groups, with percentages of 8.4%, 14.0%, 4.2%, and 0.0%, and differences also were not statistically significant (P\u0026thinsp;=\u0026thinsp;0.131). Complications outside the respiratory system were mainly Cardiovascular failure and neurological complications. In our study, the incidence rates of these two types of complications were extremely low, with only one case occurring for each.Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePatient Complications\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eComplication\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGroup A\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGroup B\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGroup C\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGroup D\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eStatistical Value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;167\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;86\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;24\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;25\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePneumonia(n,%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e132(79.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e61(70.9%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e19(79.2%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e21(84%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.947\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.400\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSevere Pneumonia(n,%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e16(9.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e12(14.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1(4.2%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0(0.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.847\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.158\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRespiratory failure(n,%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e14(8.4%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e12(14.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1(4.2%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0(0.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.126\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.131\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCardiovascular failure(n,%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0(0.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1(1.2%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0(0.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0(0.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSeizure(n,%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0(0.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0(0.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1(4.2%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0(0.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Co-infections\u003c/h2\u003e \u003cp\u003eCo-infection is a common phenomenon among patients with pertussis, especially co-infection with bacterial or viral infections. In our study, bacterial co-infection rates were most common in all four groups, with percentages of 46.1%, 38.4%, 45.8%, and 44.0%, respectively, and showed a non-significant trend (P\u0026thinsp;=\u0026thinsp;0.698). However, the rates of bacterial co-infection among the four patient groups did not decrease with increasing antibody levels, showing no significant difference. This phenomenon was also observed in the incidence of viral co-infections, with rates common in all four groups, with percentages of 22.8%, 30.2%, 25.0%, and 28.0%, respectively, and showed a non-significant trend (P\u0026thinsp;=\u0026thinsp;0.623). These results suggest that the level of antibodies does not affect the occurrence of bacterial or viral co-infections.Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eco-infection with bacterial or viral\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCo-infection\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGroup A\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGroup B\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGroup C\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGroup D\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eStatistical Value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;167\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;86\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;24\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;25\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ebacterial coinfection(n,%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e77(46.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e33(38.4%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e11(45.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e11(44.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.431\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.698\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eviral coinfection(n,%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e38(22.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e26(30.2%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6(25.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7(28.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.762\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.623\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003ePertussis remains a significant public health concern, particularly in regions with lower vaccination rates. Vaccination serves as an effective preventive strategy, fundamentally because it stimulates the production of anti-PT IgG antibodies, which are crucial for protecting against pertussis\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e.Following widespread vaccination, the incidence and mortality rates have greatly improved. However, numerous children remain unvaccinated against pertussis due to varying local policies on the minimum age for vaccination, being below the recommended age, illness, and other family-related factors.Those who have not been vaccinated face a higher risk of infection when exposed to pertussis compared to those who have received the vaccine. The severity of the disease is also greater after infection.The primary reason is that persons who lack PT IgG are susceptible to pertussis\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAmong the 302 enrolled Chinese pediatric patients who were not vaccinated, 55.30% of the children had antibody levels of 5.00IU/ml or below, while 83.77% of the patients had antibody levels of 50.00IU/ml or below. Only 16.23% had antibody levels exceeding 50.00IU/ml. This suggests that the acute-phase antibody levels among Chinese children with pertussis who are not vaccinated are generally low.This phenomenon is considered to possibly relate to the generally low antibody levels among the population in our country. Research by Qing-Hong Meng et al. indicates that newborns in Beijing generally lack protective antibodies and are vulnerable to pertussis, with 66.5% of newborns having PT-IgG levels below 5IU/ml\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e.Zhiyun Chen et.al research indicates that the geometric mean concentration (GMC) and median concentration of anti-PT IgG antibodies were 1.72 IU/mL and 1.43 IU/mL among infants under 3 months of age\u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e.Additionally, there is also a low seropositivity rate for anti-PT IgG, particularly among school-aged children\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eStudies indicating that the risk of mortality in severe pertussis, particularly among females, is higher than in males\u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e.In our study, males predominated, with only 130 female participants. There was no significant difference between females and males across the groups (P\u0026thinsp;=\u0026thinsp;0.437). This may be considered in the context that all patients in our study were from general wards and there were no fatal cases. Previous studies have shown that the severity and mortality rates among females are higher than in males, primarily within the group of severe pertussis patients.\u003c/p\u003e \u003cp\u003eElevated WBC counts and lymphocytosis are common phenomena in patients with pertussis, and significant leukocytosis (Hyperleukocytosis) is a risk factor for death in patients with pertussis\u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e.PT is a central factor driving the pathogenesis of pertussis. It is also considered to be the main cause of leukocytosis\u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e.However,serum IgG against PT, whether induced by disease or vaccination, was both essential and sufficient for immunity to pertussis\u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e.In our study, we found that the highest WBC count and highest lymphocyte count decreased with increasing antibody levels, and the differences were significant (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001; P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). This suggests that higher antibody levels are associated with lower peak values of WBC and lymphocytes, indicating that higher antibody levels may be linked to a lower severity of the disease.In our study, however, we did not observe this phenomenon clinically. We found no significant differences in the highest heart rate and highest respiratory rate among patients (P\u0026thinsp;=\u0026thinsp;0.379, 0.963), and a similar situation was observed with complications. The incidence rates of pneumonia, severe pneumonia, and respiratory failure were also not significantly different among the groups (P\u0026thinsp;=\u0026thinsp;0.400, 0.158, 0.131).\u003c/p\u003e \u003cp\u003eC-reactive protein and procalcitonin are important indicators of the inflammatory state, especially when the body is in an infectious state. In our study, the rate of Raised C-reactive protein was extremely low, and there was no significant relationship between it and antibody levels. Not only for C-reactive protein, but we also found no significant relationship between the rate of Raised procalcitonin and antibody levels. The study found that compared with simple pertussis infection, the clinical symptoms after co-infection were more severe\u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e, in our study, there was no significant difference in the rate of bacterial or viral co-infection among the four groups of patients, suggesting that the level of antibodies had no significant impact on the occurrence of co-infection, which also indirectly indicates that there is no significant relationship between antibody levels and disease severity.\u003c/p\u003e \u003cp\u003eIn our study, significant differences were observed in hospital length of stay, highest WBC count, and highest lymphocyte counts, but the incidence rates of clinical complications (pneumonia, severe pneumonia, respiratory failure), the rates of elevated inflammatory markers, and the rates of concurrent bacterial or viral infections showed no significant differences. It is currently believed that the production of a large number of anti-PT IgG antibodies after vaccination or infection should provide sufficient protection\u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e. However, the neutralizing power of antibodies is overlooked, and it is also believed that high antibody concentrations do not always guarantee good neutralizing ability \u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e. This seems to explain the phenomenon observed in our study: the level of antibodies did not affect the clinical severity of the disease. It is hypothesized that pertussis antibodies may not play as significant a role in protecting against ordinary rather than severe cases of pertussis. This also reminds us that clinicians should not solely rely on the level of antibodies to predict the severity or prognosis of a patient's disease.\u003c/p\u003e \u003cp\u003eIn this study, we observed that in unvaccinated pediatric patients with acute-phase pertussis, higher PT-IgG levels are associated with shorter hospital stays, lower WBC counts, and lower lymphocyte counts, indicating an attenuated inflammatory response. However, the PT-IgG levels did not significantly impact the severity of complications, elevation of inflammatory markers, or incidence of coinfections, suggesting that while higher antibody levels can reduce inflammation, they do not necessarily mitigate the overall severity of the disease.\u003c/p\u003e \u003cp\u003eThis study provides insights into the relationship between PT-IgG levels and pertussis severity in unvaccinated Chinese children. Despite the protective role of PT-IgG, higher antibody levels do not appear to significantly reduce the severity, highlighting the importance of vaccination to prevent the disease rather than relying on natural antibody production post-infection. Further research is needed to fully understand the immunological mechanisms and the potential benefits of higher PT-IgG levels in the management of pertussis.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eDeclaration : No funding\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAuthor (first author): Chuan Gan Contributions: WParticipate in the treatment of patient, acquired, analyzed and interpreted the data and draft the manuscript. Author (corresponding author): Gaihuan ZhengContributions: Revised the important intellectual content in the article; and approved the final submitted version\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAll data included in this study are available upon request by contact with the corresponding author\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eTaranger J, Trollfors B, Lagerg\u0026aring;rd T, Sundh V, Bryla DA, Schneerson R, et al. Correlation between pertussis toxin IgG antibodies in postvaccination sera and subsequent protection against pertussis. 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J Infect Dis. 2014;209(7):982\u0026ndash;5. doi: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1093/infdis/jit639\u003c/span\u003e\u003cspan address=\"10.1093/infdis/jit639\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStraney L, Schibler A, Ganeshalingham A, Alexander J, Festa M, Slater A, et al. Burden and Outcomes of Severe Pertussis Infection in Critically Ill Infants. Pediatr Crit Care Med. 2016;17(8):735\u0026ndash;42. doi: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1097/PCC.0000000000000851\u003c/span\u003e\u003cspan address=\"10.1097/PCC.0000000000000851\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStorsaeter J., Hallander H.O., Gustafsson L., Olin P. Levels of anti-pertussis antibodies related to protection after household exposure to Bordetella pertussis. Vaccine. 1998;16:1907\u0026ndash;1916.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVan der Lee S., van Rooijen D.M., de Zeeuw-Brouwer M.L., Bogaard M.J.M., van Gageldonk P.G.M., Marinovic A.B., et al. Robust Humoral and Cellular Immune Responses to Pertussis in Adults after a First Acellular Booster Vaccination. Front. Immunol. 2018;9:681\u0026ndash;690. doi: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3389/fimmu.2018.00681\u003c/span\u003e\u003cspan address=\"10.3389/fimmu.2018.00681\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarkoff AM, Knuutila A, Mertsola J, He Q. Evaluation of Anti-PT Antibody Response after Pertussis Vaccination and Infection: The Importance of Both Quantity and Quality. Toxins (Basel). 2021;13(8):508. doi: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3390/toxins13080508\u003c/span\u003e\u003cspan address=\"10.3390/toxins13080508\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang Y., Li Y., Chen Z., Liu X., Peng X., He Q. Determination of serum neutralizing antibodies reveals important difference in quality of antibodies against pertussis toxin in children after infection. Vaccine. 2021;39:1826\u0026ndash;1830. doi: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.vaccine.2021.02.045\u003c/span\u003e\u003cspan address=\"10.1016/j.vaccine.2021.02.045\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Pertussis, PT-IgG, Unvaccinated, Infant, Acute","lastPublishedDoi":"10.21203/rs.3.rs-4789734/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4789734/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground：\u003c/strong\u003eVaccination-induced PT-IgG offers protective effects against pertussis, and there is an inverse correlation between antibody levels and disease severity. However, there is limited research exploring the relationship between PT-IgG levels and disease severity in unvaccinated children with acute pertussis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethod：\u003c/strong\u003eThis study collected data from 302 unvaccinated children with acute pertussis. The aim was to investigate the relationship between disease-induced PT-IgG levels and the severity of pertussis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResult：\u003c/strong\u003e302 patients were divided into four groups based on their antibody levels. Most patients (83.77%) had antibody levels below 50.00IU/ml, while a smaller portion (16.23%) had levels above 50.00IU/ml. The length of hospital stay decreased significantly as antibody levels increased (P=0.044). Similar trends were observed for the highest WBC and Lymphocyte count during infection; and these differences were statistically significant (P\u0026lt;0.001 for both). There were no significant differences in the highest heart rate and respiratory rate among the patients (P=0.379 and P=0.963, respectively);Complication, including pneumonia, severe pneumonia, and respiratory failure, also showed no significant differences among the groups (P=0.400, P=0.158, and P=0.131, respectively).Raised C-reactive protein and raised Procalcitonin levels did not differ significantly between the groups (P=0.285 and P=0.170, respectively). Additionally, there were no significant differences in bacterial or viral co-infection rates among the groups (P=0.698 and P=0.623, respectively).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion：\u003c/strong\u003eIn Chinese infant patients with acute pertussis who have not received vaccination, the PT-IgG levels are predominantly below 50.00IU/ml. Despite the protective role of PT-IgG, higher antibody levels do not appear to significantly reduce the severity.\u003c/p\u003e","manuscriptTitle":"Correlation between Pertussis Toxin IgG and Severity of Pertussis in Unvaccinated Chinese infant patients with acute pertussis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-27 19:21:25","doi":"10.21203/rs.3.rs-4789734/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"26ce163d-5c40-4c04-a0b2-9d4577a1de56","owner":[],"postedDate":"August 27th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":36419848,"name":"Health sciences/Diseases/Infectious diseases/Bacterial infection"},{"id":36419849,"name":"Biological sciences/Immunology/Antimicrobial responses"},{"id":36419850,"name":"Biological sciences/Immunology/Applied immunology"},{"id":36419851,"name":"Biological sciences/Immunology/Infectious diseases"}],"tags":[],"updatedAt":"2024-09-24T14:24:20+00:00","versionOfRecord":[],"versionCreatedAt":"2024-08-27 19:21:25","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4789734","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4789734","identity":"rs-4789734","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}