Anti-nucleocapsid Antibody Response After Two Doses of CoronaVac® Among Healthcare Workers

Introduction: The Coronavirus disease-2019 (COVID-19) pandemic that started over two years ago has led to high mortality and morbidity. Vaccine studies have been initiated worldwide to end the pandemic, and the CoronaVac (R) vaccine was first administered to healthcare workers at high risk of COVID-19 in Turkey. In our study, we aimed to investigate serum antibody levels after vaccination. Materials and Methods: Volunteer healthcare workers without COVID-19 disease who received two doses of CoronaVac (R) vaccine 28 days apart and were at least 14 days after the last dose of vaccine were included in this study. Assessment of antibodies against Severe acute respiratory syndrome-Coronavirus-2 (SARS-CoV-2) in blood samples from participants was performed using the Elecsys (R) anti-SARS-CoV-2 electrochemiluminescence immunoassay. Samples with a cut-off index (COI) (COI;signal sample/cut-off) <1.0 were considered negative;whereas samples with COI >= 1.0 were deemed positive. Results: A total of 269 healthcare workers, 168 women (62.5%), were included in our study. The mean age of the participants was 37.7 +/- 8.6 (minimum-maximum: 21-62). Antibody levels were positive in 188 (69.9%) of the participants. The median antibody level was 9.2 COI (interquartile ranges=3-34.7). In terms of mean age, the mean age of participants with negative antibodies was higher with a statistically significant difference (p=0.001). The antibody positivity rate of women was higher than that of men (p<0.001). No statistically significant association was found between the time elapsed after vaccination, presence of comorbidities, development of post-vaccine side effects, and antibody levels. It was found that one or more side effects developed in 45.7% of the participants after vaccination. Conclusion: Our study showed that seropositivity developed significantly in healthcare workers after the CoronaVac (R) vaccine. It emphasizes the importance of maintaining infection prevention and control measures and administering the SARS-CoV-2 vaccine for healthcare workers at high risk.