Assessing breakthrough infections: Covishield (late schedule) versus Covaxin - A prospective comparative analysis in the general population.

Abstract

Breakthrough infections (BTI) threaten the progress of the COVID-19 vaccination program towards pandemic control. To better understand the future vaccine, knowing the BTI in the general population over a while is important. The study aimed to compare the BTI among the general population after 1 year of completion of the primary series of Covishield and Covaxin. This hospital-based prospective study was conducted among the general population beneficiaries of a COVID-19 vaccination center. Clients aged 18 years or above who had completed second vaccine dose were enrolled using systematic random sampling and followed up for 1 year. Using a semi-structured questionnaire, participants were telephonically interviewed within 1 month, 6 months, and 12 months of the second vaccine dose. Out of 1682 participants who completed the study, 958 (57.0%) and 724 (43.0%) participants received Covaxin and Covishield, respectively. Twenty-nine (3.0%) Covaxin recipients and 25 (3.5%) Covishield recipients reported BTI after 1 year of follow-up with no statistically significant difference among both groups (<i>p</i>-0.624). The binary logistic regression model showed that participants with either diabetes or hypertension had 1.22 times the risk of BTI compared to those without comorbidities (aOR: 1.219, CI: 0.072-20.716, <i>p</i>-0.891). BTI was not significantly associated with the type of vaccine, sex, employment status, and age category of the participants. The study suggests that regardless of the type of vaccine received, the population will be at the same risk and require similar future containment strategies.