Breakthrough COVID-19 Infection Among the General Community, Frontline Workers, and Healthcare Workers During the Second and Third Wave in North India: A Longitudinal Study.

Background: Vaccination is among the most important public health tools for preventing the harm caused by communicable diseases. This was particularly true in the case of COVID-19 vaccination during the COVID-19 pandemic. However, no vaccine is 100% effective, and all carry the risk of breakthrough infection in vaccinated individuals.

Methods: This longitudinal observational study was done on COVID-19-vaccinated individuals at a vaccination site in a tertiary care hospital. The study participants were categorized into the general community, frontline workers, and healthcare workers and were followed up during the study period from June 2021 to May 2022 post-vaccination. They were interviewed by telephone regarding adverse effects and breakthrough infections post-vaccination during the second and third wave of the COVID-19 pandemic in India. Incidence of breakthrough infection was calculated in all three categories after they received their first, second, and booster doses of vaccination.

Results: Fever was the most common adverse effect among all the categories of participants after the first and second doses. Incidence of breakthrough infection after the second dose of vaccination among frontline workers (RR: 5.7, 95% CI: 0.7-44.2) and healthcare workers (RR: 18.9, 95% CI: 2.6-138.6) was observed to be higher compared to the general community, but no such difference was observed among the three categories after the first dose of vaccination.

Conclusions: The incidence of breakthrough infection was found to be the highest in healthcare workers, followed by frontline workers compared to the general community, justifying their work profile and the risk associated with it.