SARS-COV-2 vaccine: First-month results of a six-month follow-up study

Background/aim Various COVID-19 vaccines are being developed around the world. Important questions to be answered regarding vaccines are efficacy, safety, and whether antibodies are protective when used in different communities. This study aimed to determine seroconversion rates of the inactivated SARS-CoV-2 vaccine in healthcare workers in a hospital and short-term adverse events due to the vaccine. Materials and methods The study carried out in Cukurova University, Turkey, comprised 282 healthcare workers who received two doses of the inactivated SARS-CoV-2 vaccine administered in two 3 µg doses, 28 days apart. On day 28 after the second dose, anti-S-RBD IgG and total anti-spike and anti-nucleocapsid IgM and IgG antibodies against SARS-CoV-2 were detected by using in vitro chemiluminescence immunoassay method. Results The mean age of participants was 39.06±10.65 (min 21; max 65) with 43.6% males and 56.4% females. On day 28 after the second dose, the seroconversion rates were found to be 92.9% for total anti-spike and anti-nucleocapsid IgG and 15.2% for IgM and 98.2% for anti-S-RBD IgG antibodies and having natural COVID-19 prior to vaccination, age and comorbidity were found to be significant factors for immunogenicity. The incidence of at least one adverse event was found as 29.8% after the first dose and 24.1% after the second dose, with the most common events being pain at the injection site, weakness, fatigue and headache. Conclusion On day 28 after the second dose of 3 ?g of the inactivated SARS-CoV-2 vaccine administration, a high rate of seroconversion was observed with no serious adverse event. Prior natural COVID-19 history, age and comorbidity were significant contributors to the formation of a strong immune response. It can be concluded that a third dose may be considered in people aged 50 years and older and those with comorbidities.