Three scientists of an advisory group on COVID-19 vaccination in the country said that they did not back the government's decision to double the interval between two doses of the Covishield shot, Reuters reported.
Three members of the advisory body told Reuters that the Indian government doubled the gap between the two doses of the AstraZeneca COVID-19 vaccine without the agreement of the scientific group that it said recommended the increase.
MD Gupte, a former director of the state-run National Institute of Epidemiology, told Reuters that the NTAGI had backed increasing the dosing interval to 8-12 weeks, the gap advised by the World Health Organization. But, he added, the group had no data concerning the effects of a gap beyond 12 weeks.
“Eight to 12 weeks is something we all accepted, 12 to 16 weeks is something the government has come out with,” Gupte said. “This may be alright, may not be. We have no information on that.” His NTAGI colleague Mathew Varghese also said that the group’s recommendation was only for 8-12 weeks.
On May 13, the Union Health Ministry increased the gap between two doses of the vaccine, from the recommended interval of six to eight weeks to 12-16 weeks.
Soon after their statements, Chairman of India's COVID-19 Working Group of NTAGI, Dr N K, Arora said that discussions are underway whether India should revert to four or eight weeks interval for Covishield vaccine and the emerging evidence regarding efficacy of partial versus full immunisation is also being considered.
He stressed that the decision to increase the gap between two doses of Covishield from 4-6 weeks to 12-16 weeks was based on scientific decision and there was no dissenting voice among the National Technical Advisory Group on Immunisation (NTAGI) members.
"COVID-19 and the vaccination are very dynamic. Tomorrow, if the vaccine platform tells us that a narrower interval is better for our people, even if the benefit is 5%-10%, the Committee will take the decision on the basis of merit and its wisdom.On the other hand, if it turns out that the current decision is fine, we will continue with it," Arora said.
The decision to increase the gap lay in the fundamental scientific reason regarding behaviour of adenovector vaccines, a Health Ministry statement quoted him as telling DD News.
Dr Arora said the earlier decision of four weeks was based on the bridging trial data available then. He also cited that the increase in gap between two doses was based on studies that showed higher efficacy with increase in gap.
Initial studies on Covishield were very heterogeneous. Some countries like the UK went for a dose interval of 12 weeks when they introduced the vaccine in December 2020, he said.
"While we were privy to this data, when we had to decide our interval, we went for four weeks interval based on our bridging trial data which showed good immune response. Later we came across additional scientific and laboratory data, based on which after six weeks or so, we felt we should increase the interval from four weeks to eight weeks, since studies showed that vaccine efficacy is about 57 per cent when it is four weeks and about 60% when it is eight weeks," he said.
(With inputs from PTI)
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