The Indian Council of Medical Research-National Institute of Epidemiology (ICMR-NIE) has concluded that even a single dose of the COVID-19 vaccine is effective in preventing deaths.
"Our analysis indicated that COVID-19 vaccination, even with a single dose, was effective in preventing deaths. It is necessary to increase coverage of COVID-19 vaccines, regardless of the type of the vaccines, to reduce the mortality in current, as well as in future waves of COVID-19 epidemic," the ICMR study stated.
The study was conducted on the Tamil Nadu Police. The department had been documenting vaccination of its workforce (as aggregate numbers with 0, 1, and 2 doses) and COVID-19 deaths during the second wave, along with the details of the date of hospitalization and vaccination.
In the study, the data (personal communication) were used to estimate the incidence of deaths due to COVID-19 among the vaccinated and unvaccinated police personnel.
"There are 1,17,524 police personnel working with the department of Police in Tamil Nadu. Between February 1, 2021, and May 14, 2021, 32,792 received a single dose, 67,673 received two-doses while the 17,059 did not receive any vaccine dose," the study said.
As per the ICMR study, 31 COVID-19 deaths were reported among these police personnel between April 13, 2021, and May 14, 2021 (median age: 52 yr, range: 34-58, 29 males).
"Of these 31 COVID-19 deaths, four had taken two doses of the vaccine, seven had taken one dose and the rest 20 were unvaccinated. The incidence of COVID-19 deaths among the vaccinated with zero, one, and two doses were 1.17, 0.21, and 0.06 per 1000 police personnel respectively," the study stated.
Compared to unvaccinated individuals, the relative risk of COVID-19 deaths among those receiving one and two doses was 0.18 and 0.05 respectively," it added.
The vaccine's effectiveness in preventing COVID-19 deaths with one and two doses was 82 per cent and 95 per cent respectively.
The published results of the phase-3 clinical trial of the Oxford AstraZeneca vaccine indicated an efficacy of 97.5 per cent against hospitalization.
"Observational studies conducted in different countries also indicated high effectiveness of the vaccine in preventing severe outcomes. The interim results of the BBV152 trial indicate high efficacy against preventing symptomatic disease. A cohort study conducted among healthcare workers from a tertiary care hospital in Tamil Nadu indicated a strong protective effect of two doses of vaccines against hospitalization, the need for oxygen therapy, and the need for ICU care. The results of our analyses are consistent with the published studies showing effectiveness against severe disease," it further added.
The analysis, however, has certain limitations as potential confounders, including age, comorbidities and previous exposure to COVID-19 infection could not be adjusted for, as the vaccination details were collected as aggregated numbers.
Also, the effectiveness could not be estimated separately for each vaccine.
( With inputs from ANI )
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