Armed Forces Medical Services (AFMS) has published the Vaccine effectiveness among healthcare and frontline Workers of Indian Armed Forces (VIN-WIN) cohort study in Medical Journal Armed Forces India, a peer reviewed scientific journal on July 27, 2021.

The study highlights the impact of protection against COVID-19 by COVISHIELD vaccine by analysing the effect on fresh infections and deaths.

According to the study, there was a 93 per cent reduction in fresh infections and the deaths were reduced by 98 per cent. It is possibly the largest study worldwide on COVID-19 vaccine effectiveness, so far. 

The study was largely conducted on healthy males with few co-morbid illnesses. It did not include children and the elderly.

In the Vin-WIN study, authors calculated incident rate and incident rate ration. Vaccine effectiveness was calculated as one-incident ration. Both crude and corrected rates were estimated and adjusted for the force of pandemic, second wave and the changing numbers in the three groups on the daily basis. The study was achieved at no additional cost by analysing available data. 

Corresponding author of the study, Consultant Medicine & Clinical Immunologist Air Commodore Shankar Subramanian said the biggest challenge was in dealing with the huge numbers while remaining statistically accurate. As the population moved from unvaccinated to partially vaccinated and then fully vaccinated, the numbers in each group changed on a daily basis.