Analysis of antibody titers according to anti-SARS-CoV-2 vaccination schedules, assessed through protein S, discriminated according to history of Covid-19 disease, comorbidities, age and sex. City of San Lorenzo, period October-November 2021

Introduction: Coronavirus 2019 (Covid-19) is a severe acute respiratory syndrome caused by a new coronavirus called SARS-CoV-2. Rapid and effective transmission led to its global spread, with the World Health Organization declaring it a pandemic on March 11, 2020. In spite of the little and recent information on this new disease, it was a race against time for many countries to create vaccines that would reduce the mortality rate, the hospitalization period and the rate of contagion worldwide. Viral surface protein S was identified as an optimal antigen for vaccine development.Objectives: To describe the humoral response to different anti-SARS-CoV-2 vaccination schedules, assessed by protein S, in the population of San Lorenzo, Santa Fe, Argentina.Material and Methods: The present study, of a descriptive and cross-sectional nature, was carried out based on the sampling of people who voluntarily attended the DetectAR Campaign, organized by the Municipality of San Lorenzo during the months of October and November 2021. In the selection of the sample, those who complied with the complete vaccination schedule (two doses of SP, SP+MO, AZ or SINO) were included and the measurement of antibodies in serum was performed by means of the Elecsys® Anti-SARS-CoV-2 test.Results: 319 participants were included, age was 52 ± 14 years. Anti-S antibody titers developed in 99.3% of the participants, with the exception of 0.6%, vaccinated with Sinopharm scheme. The median antibody titer against the RBD domain was 250 U/mL (250-233.4). The minimum value was 1 U/mL. Levels ≥ 250 U/mL (maximum reported level of antibody determined by the test) were found in 74.3% of participants. The SINO scheme yielded a median of 169.5 U/mL (250-33.8) and a mean of 142.2 ± 105.3 U/mL, comparatively lower than the rest of the schemes. The female sex presented a median of 203.8 ± 83.7 U/mL, while that of the male sex was 213.5 ± 78.9 U/mL. The median in participants ≥ 65 years was 250 U/mL (250-250) and in subjects ≤ 64 years was 250 U/mL (250-195.2). 76.5% of participants with comorbidities (n: 34) achieved peak antibody titers. 72.8% of participants who denied having had the disease (n:196) developed titers greater than 250 U/ml.Conclusions: All participants developed Anti-S antibody titers, with the exception of two participants vaccinated with Sinopharm scheme. The population with Covid-19 (+) background presented higher antibody titers. However, no differences were found in the quantification of the Anti-S humoral response according to the variables sex, associated comorbidities or in persons ≥ 65 years with respect to the rest of the sample