Explained: Why there are demands to cut the gap between two Covishield doses

The gap between the two doses of Covishield has become a contentious issue in India as many experts have now cast doubt over India's latest decision to extend the gap between the two doses of Covishield to 12 to 16 weeks from six to eight weeks. According to a Reuters report, some scientists of the government panel did not back the decision to expand the gap, which the government on Wednesday refuted and asserted that it was a unanimous decision. But why does the gap matter so much? What is the controversy all about? And why are there demands to now narrow down the gap? Here is all you need to know.

Why does the gap matter?

The gap between the two shots matters because that's how the vaccine works. The first shot increases antibodies while the second shot is a booster one. If the second shot is delayed, the first shot gets more time to work. In April, Public Health England said the vaccine efficacy increases when the interval is 12 weeks. The United Kingdom also overcame the surge caused by the Alpha variant keeping the gap at 12 weeks.

Why are there new demands to reverse the gap?

Two-three days after India increased the gap between the two Covidhsield doses, new studies emerged claiming that the single dose of Covishield gives only 33 per cent protection, not 65 to 85%, which was estimated earlier. Several countries are now reducing the gap once again.

From 4 weeks to 4-6 weeks to 12 to 12 to 16 weeks: govt clarifies

In a detailed statement, the chairman of the National Technical Group on Immunisation, Dr NK Arora said all this decision to change the gap between the two doses have been based on studies available at hand.

The first decision to keep a gap of four weeks between the two doses of Covishield was based on the bridging trial data. "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. 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% when it is four weeks and about 60% when it is eight weeks.” Dr Arora said.

Will India now reduce the gap between the doses of Covishield?

The government has said whatever decision is taken, paramount importance will be given to the health and protection of the community. “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," he said.

Sign on to read the HT ePaper epaper.hindustantimes.com