Hyderabad: A study found that COVID-19 vaccines reduce mortality by 50 per cent in patients infected with the Delta variant of the virus. It also found that mortality in individuals who had received only one dose of vaccine was similar to those who were unvaccinated and added that both Covishield and Covaxin are effective in preventing disease severity and mortality against the Delta variant in vaccinated people.

The study, titled "Clinical outcomes in vaccinated individuals hospitalized with Delta variant of SARS-CoV-2", was conducted by AIG Hospitals, Hyderabad, CSIR-Centre for Cellular and Molecular Biology, and Asian Healthcare Foundation.

The study also said that the preliminary results indicate that both Covishield and Covaxin offer protection and have comparable efficacies against the Delta variant resulting in a reduction of the disease severity and mortality among patients administered both doses of vaccines. "Rapid and complete vaccination of the population, therefore, remains our only hope in mitigating the deadly pandemic," it added.

Study findings

The hospital-based cohort study analyzed clinical profiles and outcomes of 1,161 COVID-19 hospitalized patients in Hyderabad between 24 April and 31 May. The total number of patients vaccinated with Covishield and Covaxin was 495 and the total number of unvaccinated patients was 666. Out of 495 vaccinated patients, 251 received Covishield (168 single dose and 83 two doses) and 203 received Covaxin (99 single dose and 104 two doses). The vaccine type or the number of doses was not known for the remaining 41. A significantly higher number of patients in the vaccinated group had comorbidities such as diabetes, hypertension, and cardiovascular disease as compared to the unvaccinated group.

Viral genome sequencing revealed that above 90 per cent of patients in both groups were harbouring the Delta variant of COVID-19. Vaccinated individuals showed higher neutralizing antibodies and significantly decreased Ferritin and LDH as compared to the unvaccinated group. The severity of the disease (3.2 per cent vaccine group Vs 7.2 per cent unvaccinated group) and requirement of ventilatory support (2.8 per cent vaccine group Vs 5.9 per cent unvaccinated group) were significantly low in the vaccinated group despite the fact that these individuals had significantly higher age and risk factors.

Within the vaccinated group, neutralizing antibody response and total leukocyte counts were significantly higher, and serum Ferritin levels were significantly lower in those who received Covishield (both doses) than those who received Covaxin (both doses).

A trend of increasing antibody levels and decreasing inflammatory markers was noted in individuals who received both the doses when compared with those who received a single dose. Individuals having higher antibody titres in the unvaccinated group were found to have IgM antibodies suggesting that these were acute infections and not reinfections or breakthrough infections

"These results become even more significant in the light of higher comorbidities and age in the vaccinated group. Majority of deceased in completely and partially-vaccinated individuals had no/minimal antibody response which was comparable to unvaccinated individuals. Strategies targeting these non-responders to vaccination like additional booster doses or change of vaccine type need to be explored further," said the study.

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