Breakthrough Infection With Severe Acute Respiratory Syndrome Coronavirus 2 Among Healthcare Workers in Delhi: A Single-Institution Study.

Introduction This study aimed to determine the breakthrough infection rate of coronavirus disease 2019 (COVID-19) (severe acute respiratory syndrome coronavirus 2 {SARS-CoV-2}) infection in healthcare workers (HCWs) vaccinated with either BBV152 or AZD1222 (ChAdOx1-S) vaccine. Methods A cross-sectional analysis was conducted at a medical college and hospital complex in Delhi, India, through telephonic interviews among HCWs who had received at least one dose of a COVID-19 vaccine during January-March 2021. Breakthrough infections were operationally defined as the occurrence of COVID-19 infection ≥14 days after administration of two doses of either COVID-19 vaccine. Data were entered in Epidata 3.1 (Odense, Denmark: EpiData Association) (single entered) and analyzed with IBM SPSS version 25 (Armonk, NY: IBM Corp.). A p-value < 0.05 was considered statistically significant. Results We enrolled 325 HCWs with a mean (SD) age of 29.1 (9.9) years including 211 (64.9%) males and 114 (35.1%) females. A total of 37 (13.3%, 95% CI 9.8, 17.7) COVID-19 breakthrough infections were observed in the HCWs. Additionally, 20 (6.1%) non-breakthrough infections were reported in the HCWs who were vaccinated with at least a single dose of a COVID-19 vaccine, or both doses, but prior to 14 days since the administration of the second dose. Most breakthrough infections were mild without needing supplemental oxygen for recovery. Conclusion Nearly one in seven HCWs experienced a COVID-19 breakthrough infection in the present study. A history of SARS-CoV-2 natural infection followed by at least one dose of COVID-19 vaccination was associated with significant protection against breakthrough infections.