Covaxin 50% effectiveness against Delta Covid 'not bad': Experts
November 26, 2021 12:06
The decline in the effectiveness of Covaxin, India's indigenous COVID-19 vaccine, from 77.8 per cent to 50 per cent during a Delta-driven case surge in April and May this year is neither bad nor surprising, say scientists.
The differing figures led to some concern, particularly among those who had received Covaxin, but several scientists allayed the misgivings, pointing to the potency of the Delta strain, the intensity of the second Covid wave in India and the level of exposure among healthcare workers.
The results of the first real-world assessment of Covaxin published in The Lancet Infectious Diseases journal on Wednesday showed that two doses of the vaccine, also known as BBV152, are 50 per cent effective against the symptomatic disease.
The study assessed 2,714 hospital workers at the All India Institute of Medical Sciences (AIIMS) in Delhi, from 15 April to 15 May, who were symptomatic and underwent RT-PCR tests.
Earlier, an interim study based on Phase 3 clinical trials showed that two Covaxin doses had 77.8 per cent efficacy against symptomatic disease and present no serious safety concerns.
One possible reason for this drop is also infection period when Delta variant was the most prominent. The original 77 per cent figure is for Wuhan strain.
In general, all vaccines are at least marginally less effective against the Delta variant as compared to Wuhan strain, said Vineeta Bal from Pune's Indian Institute of Science Education and Research. Immunologist Satyajit Rath added that it is not clear whether the decrease in protection between the two studies is a real difference. -- PTI
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