Breakthrough Infections: Clinical Profile and Outcomes of COVID-19 Vaccinated and Unvaccinated People From a Tertiary Care Hospital.

Introduction Despite the availability of a vaccine and extensive vaccination, breakthrough infections are commonly noted, which is jeopardizing the vaccine-based protection against COVID-19. The present study aims to evaluate COVID-19 breakthrough infections and to compare the clinical profile and outcomes of the vaccinated and unvaccinated populations.  Methods A retrospective observational study was conducted for two months (March-April 2021), and all cases reported during the study period were included in the study. Socio-demographic details, COVID-19 profiles, clinical outcomes, vaccination statuses, and types of vaccine were collected from the patients. Further, COVID-19-positive samples were screened for lineages using next-generation sequencing (NGS). Results Of the total 103 patients included in the study, 79 (76.7%) were symptomatic and 24 (23.3%) were asymptomatic. Only 32% were vaccinated and 68% were unvaccinated. 29.2% were hospitalized due to COVID-19 and all of them were unvaccinated. The mortality among hospitalized patients was extremely high (60%). The time to positivity after complete vaccination was noted to be 37.09±23.74 days. The unvaccinated study participants showed lower Cycle threshold (Ct) values (E Gene/N Gene: 17.38±4.53) as compared to the vaccinated people (E Gene/N Gene: 22±4.25). The Delta (B. 1.1. 629) (76.7%) was the predominant variant among the study population followed by AY.4 (20.4%) and Kappa (2.9%) variants. Conclusion Although the vaccination does not restrict/avoid infection, it appears to protect the vaccinated people from severe forms of COVID-19. Also, the higher Ct values among vaccinated people indicate that the viral load among such people may be lower and, therefore, minimizes viral transmission.