Effectiveness of COVID-19 Vaccines against SARS-CoV-2 Infection in a Healthcare Worker Cohort: A Prospective Study

Introduction: A vaccine's ability to protect against disease acquisition is considered one of its most important aspects of effectiveness. The present study aimed to determine the effectiveness of COVID-19 vaccines among healthcare workers (HCWs). Materials and Methods This was a prospective cohort study conducted with HCWs from April 2021 to May 2022. We investigated the effectiveness of the AZD1222, Sinopharm, and Sputnik V vaccines against SARS-CoV-2 infection (diagnosed by PCR testing). For this purpose, vaccination data from 3365 HCWs were collected, and vaccine effectiveness was estimated via multivariable Cox models and the incidence rate of SARS-CoV-2 infection per 100,000 person-time. Result Among the 3365 participants, all individuals received at least one dose, 95.3% received at least two doses, and 36.7% of those who received two doses also received three doses of the COVID-19 vaccine. The overall vaccine effectiveness after three doses was estimated to be 92% (95% confidence interval: 81–97). The effectiveness of the AZD1222, Sinopharm, and Sputnik V vaccines after three doses was estimated to be 98% (95% confidence interval: 96–97), 93% (95% confidence interval: 42–99), and 83% (95% confidence interval: 13–97), respectively. Conclusion The results of this study indicate that completing vaccination and receiving second and third doses significantly increased vaccine effectiveness and was highly effective in preventing SARS-CoV-2 infection in HCWs. Furthermore, among the vaccines investigated, vaccination with three doses of the AZD1222 vaccine showed the highest effectiveness.