SARS-CoV-2 Infection Elicits A Greater Humoral Immune Response In The Second Wave Than The First Wave In Morocco

Purpose: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the ongoing pandemic of coronavirus disease 2019 (COVID-19). One year has passed since the first COVID-19 case, and concerns have emerged regarding new variants, meaning that characterizing antibody-mediated immune response dynamics is of paramount importance. Here, we evaluated the humoral immune response against SARS-CoV-2 in subjects during the first and second waves of the pandemic in Morocco. Methods: We assessed humoral immune response in samples from 94 seropositive individuals in the first wave (February to August 2020) and 596 seropositive individuals in the second wave (December 2020 to January 2021). Plasma samples were collected from volunteer blood donors and their levels of serum IgG to SARS-CoV-2 nucleoprotein (NP) were determined using architect SARS-CoV-2 IgG chemiluminescence microparticle immunoassay. Results: Our results revealed an increase of humoral immunity during the second wave than first wave (3.897 ± 0.079 vs. 2.842 ± 0.153, respectively, p<0.0001). Notably, we found an age-related gradient in antibody level, with higher antibody index in subjects at 45 years old and above (p= 0.01451). However, no significant difference was found according to gender (p= 0.8629). Conclusions: Our data highlighted an important issue regarding antibody-mediated immune response against SARS-CoV-2 infection during the second wave and this issue might have arisen due to the dynamics of different strains circulating during the progress of the pandemic.