Covid vaccines 95% effective in preventing deaths, data from Tamil Nadu Police shows

Researchers from ICMR & CMC Vellore who studied the data said the number of Covid deaths among those not vaccinated was 1.17 for every 1,000 people.

Representative Image | A health worker draws out a vaccine dose from a vial | Bloomberg

New Delhi: Vaccine effectiveness in preventing Covid deaths with two doses is as high as 95 per cent, with even a single dose of both Covaxin and Covishield having the potential to lower the risk of death from the infection, according to a study by ICMR and CMC Vellore researchers.

The researchers analysed data from police personnel in Tamil Nadu for the study, published in the Indian Journal of Medical Research (IJMR).

While clinical trials have been conducted for both vaccines, information regarding the real world effectiveness of Covid vaccines, especially for preventing severe disease, is currently limited in India.

According to the researchers, such data would also help address the issue of vaccine hesitancy, which has been a major hurdle for the vaccination drive in Tamil Nadu.

The Tamil Nadu Police department has been documenting vaccination of its workforce and Covid deaths during the second wave, along with details of the date of hospitalisation and vaccination.

Vaccine & mortality rate

In the IJMR study, this data was used to estimate the incidence of deaths due to Covid-19 among vaccinated and unvaccinated police personnel.

The incidence of mortality among vaccinated and unvaccinated individuals was compared to calculate the relative risk of mortality associated with Covid-19 vaccination.

Of the 117,524 police personnel working with the police department in Tamil Nadu, 32,792 received one dose, while 67,673 received two doses between 1 February 2021 and 14 May 2021. The remaining 17,059 did not receive even a single dose.

There were a total of 31 Covid deaths reported among these police personnel between April 13 and May 14 this year.

Of these 31 deaths, four had taken two doses of the vaccine, seven had taken one dose and the remaining 20 were unvaccinated.

This means the number of Covid deaths among those not vaccinated was 1.17 for every 1,000 people. Among those who had received one dose, the death rate was 0.21 per 1,000 people. After both doses of the vaccine, 0.06 deaths per 1,000 police personnel were recorded.

Most of the Indian population have received either the ChAdOx1 vaccine — Oxford-AstraZeneca vaccine manufactured by the Serum Institute of India — or BBV152 (Covaxin), developed by ICMR and Bharat Biotech.

Vaccine effectiveness

According to the researchers, the vaccine effectiveness in preventing Covid deaths with single and both doses was 82 per cent and 95 per cent, respectively.

The published results of phase 3 clinical trial of Oxford-AstraZeneca vaccine indicated an efficacy of 97.5 per cent against hospitalisation.

“The results of our analyses are consistent with the published studies showing effectiveness against severe disease,” the team wrote in the report.

The researchers acknowledged certain limitations to the study. They were not able to gather details about comorbidities and previous Covid infections.

The effectiveness of the two different vaccines could not be estimated separately.

However, the team reiterated that even a single dose of Covid vaccination was effective in preventing deaths.

“It is necessary to increase coverage of COVID-19 vaccines, regardless of the type of vaccines, to reduce mortality in current as well as future waves of COVID-19 epidemic,” the study noted.