KINETICS OF ANTI-SARS-COV-2 IGG ANTIBODIES POST-COVID-19 -VACCINATION

INTRO: During the pandemic of COVD-19, several vaccines have been developed and are currently used worldwide. However, head-to-head studies comparing various vaccines are limited. Therefore, This single-center, prospective, realworld study. head-to-head study of compared the effectiveness of BNT162b2 (Pfizer BioNTech), mRNA-1273 (Moderna) ChAdOx1-S (Astra Zeneca) vaccines. The kinetics of SARS-CoV2 spike antibodies were monitored post-vaccination and following two booster doses in COVID-19 naïve and previously infected adults. METHODS: The primary outcome was the emergence of virologically positive COVID-19 cases after vaccine completion. The secondary outcome was the occurrence of postvaccination COVID-19-related hospitalizations. The titers of anti-SARS-CoV-2 IgG antibodies against the S1 subunit of the virus's spike protein were measured after the first and second doses of the three vaccines and the booster doses. FINDINGS: The current study enrolled and followed 1550 participants who received ChAdOx1-S or BNT162b2, or mRNA-1273, and 1550 non-vaccinated subjects between March 2021 and February 2022. After completing two vaccine doses, the effectiveness in preventing COVID-19 cases was 89.2%, 95.5%, and 94.6% for ChAdOx1-S or BNT162b2, or mRNA-1273, respectively. Four COVID-19-related hospitalizations (0.26%) were reported in the vaccinated versus 648 (41.81%) non-vaccinated participants (P<0.0001). Following the Pfizer booster dose, no COVID-19-positive cases or hospitalizations were reported. In the three vaccines, SARS-CoV2 antibody titers increased gradually after the first dose, peaked 3-4 weeks after the second dose, then declined after 28-32 weeks. Enhanced antibody response was observed after the booster dose and was maintained until the end of follow-up. Comorbidities were associated with lower antibody titers, particularly diabetes, autoimmune diseases, and advanced renal diseases. CONCLUSION: The study showed that the three COVID-10 vaccines effectively reduced the risk of virologically confirmed COVID-19 disease and prevented severe illness and hospitalizations in COVID-19 naiive and previously infected. Booster doses enhance the SARS-CoV2 antibody response and decrease the incidence of virologically proven severe COVID-19.