Three scientists of an advisory group on Covid-19 vaccination in the country have said that they did not back the Centre’s decision last month to double the interval between two doses of the Covishield shot, Reuters reported on Tuesday.

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. The Centre had said then that the decision was recommended by the the country’s Covid Working Group and was backed by the National Technical Advisory Group on Immunisation, or NTAGI.

The three scientists, who are part of the 14 “core members” of the NTAGI, have now said that the group did not have enough data to make such a recommendation, according to Reuters.

However, soon after their statements came to light on Tuesday evening, Covid Working Group Chairman NK Arora said the decision was taken on “scientific basis” and without any “dissenting voice”.

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.

Meanwhile, JP Muliyil, a member of the seven-member Covid Working Group, said there had been discussions within the NTAGI on increasing the vaccine dosage interval but that the body had not specifically recommended the 12-16 week gap. “That specific number was not quoted,” he told Reuters.

However, NK Arora told DD News later on Tuesday that the NTAGI recommendation was that the interval has to be 12-16 weeks. “We have a very open, transparent system where decisions are taken on scientific basis,” he said. “The Covid Working Group took that decision, with no dissenting voice... [the] issue was then discussed threadbare at NTAGI meeting, with no dissenting notes.”

Arora added that scientific and laboratory data showed that vaccine efficacy went up from 57% in a four week-interval to 60% in an eight-week interval.

“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] United Kingdom,” Arora said. He added that data from the UK in April last week showed that the vaccine showed 65%-88% efficacy and that the 12-week gap helped the country in dealing with the outbreak of the Alpha variant of the coronavirus.

However, in contrast to Arora’s defence of the dosage regime, the UK had in early May reduced its mandated gap for those above 50, from 12 weeks to eight weeks. The decision was, in fact, taken in order to speed up vaccinations in the country’s bid to deal with the Delta variant of the virus, which was first identified in India.

On Tuesday, the UK reduced the gap for those above 40 too, as the country deals with a surge in Delta variant cases, which has delayed the lifting of Covid-related restrictions by four weeks.

In an interview last week, United States’ top virologist Anthony Fauci had said that extending the gap in vaccine schedule makes people “vulnerable to variants”. He also said that the rise in Delta variant cases in the UK was a result of increasing the gap.

However, days after the Indian government had extended the gap between two doses of the Covishield vaccine, Fauci had backed the move, referring to it as a “reasonable approach” to take when faced with a shortage of doses. “It is very unlikely that it would have a negative effect on the efficacy of the vaccine,” he had said.