New Delhi, June 16
Discussions are underway on whether India should have a four or eight weeks interval for the Covishield vaccine, Chairman of India’s COVID-19 Working Group of NTAGI, Dr N K Arora, said.
He also said that the emerging evidence and reports regarding the efficacy of partial versus full immunisation are also under consideration. On the decision to increase the gap between two doses of Covishield from four-six weeks to 12-16 weeks, he said the move 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 the behaviour of adenovector vaccines, a Health Ministry statement quoted him as telling DD News. In the last week of April, the data released by Public Health England, United Kingdom’s executive agency of the Department of Health, showed that vaccine efficacy varied between 65 and 88 per cent when the interval is 12 weeks.”This was the basis on which they overcame their epidemic outbreak due to the Alpha variant. The UK was able to come out of it because the interval they kept was 12 weeks. We also thought that this is a good idea since there are fundamental scientific reasons to show that when the interval is increased, adenovector vaccines give a better response. Hence the decision was taken on May 13, to increase the interval to 12-16 weeks,” he said.
This also gives flexibility to the community, since everyone cannot come at precisely 12 weeks or so, he added.
“We have a very open and transparent system where decisions are taken on a scientific basis. The COVID Working Group took that decision, with no dissenting voice. This issue was then discussed threadbare at an NTAGI meeting, again with no dissenting notes. The recommendation was that the vaccine interval has to be 12-16 weeks,” he said. 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 the gap between two doses was based on studies that showed higher efficacy with an 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.
