Should a third booster dose be scheduled after two doses of CoronaVac? A single-center experience.

Introduction In the tenth month of the pandemic, COVID-19 vaccination was given first to healthcare workers in Turkey after receiving emergency use approval from the Ministry of Health. This study, which was performed at the COVID-19 reference center in Ankara (the capital of Turkey) aimed to evaluate the seroconversion rate of the CoronaVac vaccine. The anti-spike immunoglobulin G response to the two-dose vaccination was retrospectively examined in healthcare workers who had no previous history of SARS-CoV-2 infection. Methods The post-vaccine seroconversion rate was investigated by measuring the antibody levels of healthcare workers who had received CoronaVac. Vaccination was administered as 600 SU in 28-day intervals. The healthcare workers' anti-SARS-CoV-2 immunoglobulin G levels were used to determine the seroconversion rate two months after the second dose of the vaccine. Results Of the healthcare workers, 22.9% (n = 155) were seronegative. The younger the age of the participant, the higher the level of anti-SARS-CoV-2 immunoglobulin G. Furthermore, anti-SARS-CoV-2 immunoglobulin G levels were much higher in women than men. Conclusion This study provided strong evidence for the administration of a booster dose. To the best of the authors' knowledge this is the first study in the literature on the decrease of anti-SARS-CoV-2 immunoglobulin G levels in older people. This article is protected by copyright. All rights reserved.