Real life vaccine effectiveness against COVID-19: Proof of the pudding!

Abstract

In the current COVID-19 pandemic, where most anti-viral and anti-inflammatory drugs have fallen short of passing the stringent test of Randomized Controlled Trials, therapeutic options are unfortunately limited. With variable (and often suboptimal) acceptance of public health interventions and strained/limited health infrastructure, vaccines against SARSCOV2 virus seem to be our shining hope in controlling the pandemic. Over 200 vaccine candidates are in various stages of development, with Emergency Use Authorization (EUA) having been granted to nine of themworldwide. In India, COVISHIELD® (Astra Zeneca) and COVAXIN (Bharat Biotech) were granted EUA in January 2021. While the former is a viral vector vaccine (adenovirus) carrying the genetic material of spike protein of SARS-COV-2 the latter is an inactivated SARS-COV-2 vaccine with intact proteins. Other vaccines are expected to follow. How does one assess if a vaccine is effective? This is determined by vaccine efficacy and effectiveness studies. Both types of study calculate the risk of infection and disease among vaccinated and unvaccinated persons, and determine the reduction in risk. While vaccine efficacy is studied in an ideal setting, as a prospective randomized control trial (where effect of vaccination in prevention of infection or disease can be proven), vaccine effectiveness studies are done in real world settings in prospective cohort or retrospective caseecontrol studies. While the cohort studies compare the incidence