Detection and Evaluation of Antibodies to SARS CoV-2 Spike Protein in Healthcare Workers After Inactivated COVID-19 (CoronaVac) Vaccination

Özet

Objective: Antibodies against the S protein are used to investigate post-vaccine and post-infection immunity. In this study, it was aimed to determine the antibody levels and the efficacy of the vaccine after the CoronaVac vaccine in healthcare workers. Methods: Data from 96 healthcare workers who had the CoronaVac vaccine were analyzed. From the first dose, monthly antibody measurements were made over a 5-months period with an interval of 28 days between two vaccine doses. Total antibodies (IgM and IgG) against SARS-CoV-2 were detected by the Electrochemiluminescence method using the Elecsys® Anti-SARS-CoV-2 S kit, which contains recombinant protein representing the receptor-binding site of the S1 antigen. Results: 51% (n=49) of the volunteers aged 22-69 (39.75±11.19) were female. The mean antibody concentration was 8.93 U/mL one month after the first vaccine dose, 171.30 IU/ mL one month after the second vaccine dose, 125.90 IU/mL two months after the second dose, 98.57 IU three months later, and 89.85 IU/mL after four months. Increase in antibody levels in the first and second months; The decreases in antibody levels in the in the following months were statistically significant. The proportion of subjects with antibody positivity ≥0.8 IU/mL and developing neutralizing antibodies (≥15 IU/mL) was 68.75% and 5.21% after the first dose of vaccination. The rate of individuals developing neutralizing antibodies were 100%, 93.8%, 91.7%, and 89.6% with regard to the months after the second dose of vaccination. One person had SARS-CoV-2 D3L-containing variant (UK variant) PCR positivity 9 weeks after the second vaccine dose. Conclusion: In the long-term follow-up, the neutralizing antibody level was found to be significantly higher even at the end of the 5th month, indicating that the vaccine is protective. The decrease in post-vaccination antibody concentrations and the emergence of new SARSCOV- 2 variants suggest that a booster dose may be beneficial.