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

Introduction: 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.

Aims And Objectives: The study aimed to compare the BTI among the general population after 1 year of completion of the primary series of Covishield and Covaxin.

Materials And Methods: 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.

Results: 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 (-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, -0.891). BTI was not significantly associated with the type of vaccine, sex, employment status, and age category of the participants.

Conclusion: 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.