Incidence and severity of SARS-CoV-2 virus post COVID-19 vaccination: A cross-sectional study in India

Several sociodemographic variables, including ethnic inequality, have been identified as potentially influencing the uptake of COVID-19 vaccinations. To develop herd immunity against COVID-19, at least 70-85% of the population must be vaccinated. As the situation with COVID-19 changes, the public's perception keeps fluctuating. We designed a survey to determine the prevalence of vaccinated individuals and the rate of infectivity post-vaccination. We also aimed to study the clinical manifestations and infectivity of the SARS-CoV-2 virus post-vaccination.

A cross-sectional study was conducted from May 10, 2021 to July 10, 2021 across India through a pre-tested validated semi-structured self-administered electronic questionnaire, to the study subjects with objectives explained and the confidentiality of the data and results had been assured. The questionnaires were prepared using Google forms and the link was sent across social media platforms such as WhatsApp, Facebook, and various social platforms where people are actively engaged following the restrictions and protocols of social distancing. General demographic data, followed by their lifestyle and comorbid conditions, and data on their vaccination, infectivity, and side effects were collected.

We included 2334 participants in the study, of which the majority of the study participants were in the age group of 25-34 years (38.6%). 1729 were vaccinated individuals of which 80.7% had received Covishield and 17.8% had received Covaxin. Around 61.1% have received both doses among 1729 vaccinated individuals and 38.9% had received only one dose of vaccine. The majority of the fully vaccinated individuals had a gap of 4-5 weeks for the second dose (37.1%) followed by 5-6 weeks (11.2%). Post-vaccination 50.8% had experienced muscle pain, 46% had experienced fatigue, 36.5% weakness, and 12.3% back pain. Among vaccinated 26% turned out to be COVID-19 positive and 44.5% non-vaccinated got infected. The odds of infection among non -vaccinated individuals was 2.27 times higher than vaccinated individuals. Individuals who encountered the viral antigen for the second time experienced either through vaccination or infection demonstrated exaggerated inflammatory response which is explained by the antibody-dependent enhancement phenomenon without life-threatening complications.

Although more than 50% of the vaccinated individuals experienced some form of musculoskeletal side effects, we noted a high acceptance rate (74%) of vaccination among the participants. The vaccinated individuals were two times safer from infection compared to the non-vaccinated individuals.