PremiumThe statement came in the backdrop of reports claiming that the central government doubled the gap between Covishield shots without the agreement of the scientific group
The interval between two dosages of the Covishield Covid-19 vaccine was extended based on scientific evidence and the decision was taken in a transparent manner, said NK Arora, the chairman of NTAGI, on Tuesday.
"We have a very open, transparent system where decisions are taken on a scientific basis. The Covid Working Group took that decision, with no dissenting voice. The issue was then discussed threadbare at the NTAGI meeting, with no dissenting notes," said Arora.
The chair of the National Technical Advisory Group on Immunisation explained the process that culminated in the decision.
"Initial studies on Covishield were very heterogeneous. Some countries like the UK went for 12 weeks dose interval when they introduced the vaccine. While we were privy to this, when we decided our interval, we went for four weeks interval based on our bridging trial data," he added.
He said that the bridging data showed a good immune response.
"Later, we came across additional scientific and laboratory data. Based on that after six weeks or so, we felt we should increase interval from four weeks to eight weeks since studies showed that vaccine efficacy is about 57% when it is four weeks and about 60% when it is eight weeks," said the NTAGI chair.
"At that time, we discussed why we don't increase it to 12 weeks, but we decided we should wait for ground-level data from the UK," he added.
Apart from India, the UK is the other biggest user of the AstraZeneca Covid shots.
"In April's last week, Public Health England data showed that when the interval is 12 weeks, vaccine efficacy was varying between 65-88%. UK was able to come out of it because the interval they kept was 12 weeks," said Arora.
Extended interval
The government had on 13 May said it has accepted the Covid-19 Working Group's recommendation and extended the gap between the two doses of the Covishield vaccine from 6-8 weeks to 12-16 weeks.
The recommendation of the Covid-19 Working Group was accepted by the National Expert Group on Vaccine Administration for Covid-19 (NEGVAC), headed by Dr V K Paul, member (health), Niti Aayog.
Explaining the reason behind the extension, Paul had said at a press conference as per studies, initially, the interval between two doses of Covishield was four to six weeks.
But then as more data became available secondary analysis showed increasing the dosage interval to 4 to 8 weeks can have some advantage.
Paul said the UK by that time had already extended it to 12 weeks and WHO also had said the same, but many nations still did not change the dosage pattern.
"At that time, our science-based technical committee anchored by ICMR along with DBT, by looking at the available data, felt breakthrough infections may increase if the gap is increased (to 12 weeks)," he said.
"So in good faith, based on their capability, without any pressures, they increased the dosage interval to 4 to 8 weeks. The issue was reviewed periodically again and again," he added.
Paul explained that the decision to extend the interval further was taken based on the available real-live evidence, particularly from the UK.
"This is a dynamic decision and part of periodic review," he had said.
Dissenting voices
Arora's recent statements came in the backdrop of reports claiming that the central government doubled the gap between Covishield shots without the agreement of the scientific group.
According to a Reuters reports, the NTAGI scientists, classified by the government as three of the 14 "core members", said the body did not have enough data to make such a recommendation. when the decision was announced.
MD Gupte, a former director of the state-run National Institute of Epidemiology, said the NTAGI had backed increasing the dosing interval to 8-12 weeks - the gap advised by the World Health Organization. But he added that 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," he added. "This may be alright, may not be. We have no information on that."
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