Evaluation and follow-up of antibody formation after CoronaVac vaccine

OBJECTIVE: The aim of this study was to monitor the time-dependent change by evaluating the antibody levels at the 4th, 7th, 10th, 13th, and 16th weeks after the second dose of the CoronaVac vaccine. METHODS: The study group (n=65) were between 21 and 60 years old and received two doses of the CoronaVac vaccine. Blood samples were collected after 4th, 7th, 10th, 13th, and 16th weeks of the second dose of the vaccine administration. There was a coronavirus disease 2019 recovered group (n=29) who were SARS-CoV-2 real-time PCR test result positive before the vaccination period, and no coronavirus disease 2019 history group (n=36). Age, BMI, gender, smoking, comorbidity, coronavirus disease 2019 contact history, and working in the coronavirus disease 2019 service history of the individuals were recorded. RESULTS: No statistically significant difference was found in the descriptive findings of the individuals according to coronavirus disease 2019 recovered group and no coronavirus disease 2019 history group. It was observed that antibody levels in the coronavirus disease 2019 recovered group were found to be higher for each period of serum collection compared to the no coronavirus disease 2019 history group, which were statistically significant. The distribution curves of the antibody levels according to the timing of blood collection in coronavirus disease 2019 recovered group, no coronavirus disease 2019 history group, and total subjects were extrapolated, and it was observed that the estimated time for the antibodies to reach the threshold value of the test was 214, 145, and 166 days after vaccination. CONCLUSION: It is important to make booster doses, as the CoronaVac vaccine will lose its effect after the fifth month due to the decrease in Ab levels. In addition, since the antibody levels decrease later in those who have a history of coronavirus disease 2019 infection and are vaccinated, individuals who have no previous history of coronavirus disease 2019 should be given priority for vaccination.