First real-world all-India study confirms effectiveness of Covishield and Covaxin
The results of the first comprehensive real-world study in India of the effectiveness of Covishield and Covaxin have confirmed the results of the clinical trials, though to a lesser degree of efficacy, but which, according to the lead investigator, was expected. The findings also underline the importance of continued expansion of the two-dose vaccination coverage.
A recent scientific paper has confirmed for the first time, through a comprehensive study, the effectiveness of both the COVID-91 vaccines, Covishield and Covaxin in a real-world Indian setting.
The findings are a result of an analysis by the Indian Council of Medical Research (ICMR) in 11 hospitals across 10 cities between May and July 2021, which studied severely ill and hospitalised COVID-19 patients. A total of 1,143 cases of severe infection and 2,541 negative cases were studied. The ten cities were Bhubaneswar, Chennai, Jodhpur, Kochi, Mysore, Nagpur, New Delhi, Puducherry, Rishikesh and Surat.
The study—not peer-reviewed yet but released on an online archive of research preprints, and submitted to The Lancet for publication—showed the real-world effectiveness of Covishield and the home-made Covaxin to be 80 per cent and 69 per cent, respectively. Although lower than the protection reported in clinical trials, the figures are still considered to be good.
The findings also underline the importance of continued expansion of the two-dose vaccination coverage. But the recommended gap between the two doses as per the study differs from that of the current vaccination policy.
According to the study, effectiveness was the highest with a gap of six to eight weeks between two shots, for both Covishield and Covaxin. The current vaccination policy, on the other hand, recommends a dose gap of 12 weeks for Covishield and four-to-six weeks for Covaxin.
Importantly, efficacy estimates were similar against the Delta strain and its sub-lineages: 81 per cent with Covishied and 64 per cent with Covaxin, but after two doses. After a single dose, the effectiveness was 73 per cent and 44 per cent, respectively.
Tarun Bhatnagar, an epidemiologist with the National Institute of Epidemiology (ICMR-NIE) and principal investigator for the study, told The Telegraph that the lower efficacies in the real-world studies, as compared to those documented during clinical trials, was expected.
He also said that the higher effectiveness of the vaccines with the six-to-eight-week gap is “an interesting finding”, but there is insufficient data yet to recommend that Covishield’s gap should be shortened from the 12 weeks that is officially recommended. Bhatnagar reasoned that other studies and biological principles suggest the 12-week gap has greater efficacy. It is possible that some of the people observed in the real-world study had already been infected with the coronavirus and thus carried antibodies before they received vaccinations.
