The Indian government’s decision to double the interval between two doses of the Covishield vaccine was taken in a “transparent manner” and “based on scientific data”, Union Health Minister Harsh Vardhan said on Wednesday.

His comments came after three scientists of the National Technical Advisory Group on Immunisation said they did not support the decision to increase the gap. These three scientists were classified by the government as three of the 14 “core members” of the advisory group. But, they said that the body did not have enough data to make such a recommendation.

“India has a robust mechanism to evaluate data,” Vardhan tweeted. “It is unfortunate that such an important issue is being politicised!”

On May 13, the health ministry increased the gap between two doses of the Covishield vaccine, from the recommended interval of six to eight weeks, to 12-16 weeks. The Centre had claimed that the extended gap was recommended by the National Technical Advisory Group on Immunisation, based on real-life evidence mainly from Britain.

In his tweet on Wednesday, Vardhan also attached a statement from the health ministry that quoted NK Arora, chief of the National Technical Advisory Group on Immunisation, about the changes.

Arora said the United Kingdom also kept the interval between two doses of the AstraZeneca vaccine, which is manufactured as Covishield in India, at 12 weeks.

“In the last week of April, 2021, the data released by Public Health England, United Kingdom’s executive agency of the Department of Health, showed that vaccine efficacy varied between 65% to 88% when interval is 12 weeks,” Arora said.

Arora cited the United Kingdom’s decisions related to increase in vaccine doses as it dealt with a surge in infections caused due to the Alpha variant found in the country’s Kent county. “The UK was able to come out of it because the interval they kept was 12 weeks,” the government official said. “We also thought that this is a good idea, since there are fundamental scientific reasons to show that when interval is increased, adenovector vaccines give better response.”

However, 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 United Kingdom reduced the gap for those above 40, amid a surge in Delta variant cases. The Boris Johsnon-led government has also delayed the lifting of Covid-related restrictions by four weeks.

Follow today’s live updates on the Covid-19 crisis here.

Meanwhile, Arora on Wednesday said there was no opposition to the COVID Working Group and National Technical Advisory Group on Immunisation’s decision to increase the gap.

The expert pointed out that the government’s earlier decision to maintain a gap of four to six weeks between two doses of Covishield was based on bridging trial data that was available then.

“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% when it is four weeks and about 60% when it is eight weeks.”

Arora added that the gap between doses was not extended to 12 weeks then because experts were waiting for ground-level data from the UK.

The government’s medical expert said that any decision on reducing the gap between the doses will be taken scientifically. “Covid-19 and the vaccination are very dynamic,” Arora said. “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.”

Serum Institute of India’s Covishield and Bharat Biotech’s Covaxin are the two vaccines being used in India’s inoculation drive.

The Centre has been facing pressure to speed up its inoculation drive to bring the Covid-19 situation under control. It has been criticised for the poorly-planned vaccination programme as states grappled with acute shortages of doses.

On June 7, Prime Minister Narendra Modi announced that the Centre would take charge of procuring vaccines and providing them to the states.

India recorded 62,224 new coronavirus cases on Wednesday morning, taking its overall tally to 2,96,33,105 since the pandemic broke out in January 2020. The toll rose by 2,542 to 3,79,573. The number of active cases fell below 9 lakh. India now has 8,65,432 active cases.