As reports of dissent from technical experts about increasing the gap between two Covishield doses emerged, the Union Health Ministry said a decision on the matter was taken on scientific reasoning and following a recommendation from the National Technical Advisory Group on Immunisation (NTAGI).
A Reuters report cited three experts, including Dr JP Muliyil, Dr Mathew Varghese and Dr MD Gupte, who said the government had decided to double the gap between the two doses of the AstraZeneca COVID-19 vaccine to up to 16 weeks without their consent and only discussions had taken place within the NTAGI on increasing the interval. They also said the group had no data concerning the effects of a gap beyond 12 weeks.
Even as the government asserted that it was a unanimous move, the issue taken a controversial turn and questions are being raised about why the gap between the two doses matter so much and on what grounds are demands now being made to narrow down the same. The Centre on May 13 had approved extending the gap between the two doses of the Covishield vaccine from six to eight weeks to 12 to 16 weeks at a time when reports of massive shortage of vaccine was being reported from across the country days after the immunization programme was opened for all adults.
NTAGI chairman NK Arora the decision to expand the gap to up to 16 weeks had been taken to provide “flexibility” for those who may not be able to get the second dose at 12 weeks.
Widening The Gap
The government has said the decision to raise gap was based on scientific reason about the behaviour of adenovector vaccines. Based on the real-life evidences, particularly from the United Kingdom, the COVID-19 Working Group agreed to increase the interval between two doses of Covishield Vaccine to 12 to 16 weeks, the Health Ministry said in a statement.
Why Gap Matters?
The first shot of Covishield increases antibodies while the second shot is a booster dose if the second shot is delayed, the first shot gets more time to work. In April, Public Health England had said efficacy of the vaccine rises when the interval is 12 weeks.
Days after the Union government raised the latest gap between the two doses of Covishield, new studies suggested the single dose of Covishield gives only 33 per cent protection, not 65 or 85 per cent as estimated earlier. Several countries have started reducing the interval.
What Indian Research Says?
A study conducted at the National Centre for Disease Control and the CSIR Institute of Genomics and Integrative Biology (IGIB) in New Delhi found the second wave surge in cases in the national capital was mainly caused by the Delta variant. It reportedly found that the Delta variant is 50 per cent more transmissible than the Alpha variant, or B.1.1.7 or the UK variant that had caused an earlier surge in that country.
It added that prior infection and partial vaccination were “insufficient impediments” for checking the spread of the Delta variant. Further, the researchers said that the Delta variant was “over-represented”, that is, more common, in post-vaccination breakthrough cases.
What Govt Says?
Dr Arora further said 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 was quoted as saying.
Dr Arora said any reversion in the current protocol would happen only the vaccine platform suggests any benefit out of the same. “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 five to 10 per cent, 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.
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