Single-dose of Covishield 61% effective; Revisit vaccination interval with new data: NTAGI chief

New Delhi: A single dose of Covishield is 61% effective over the “Delta” variant, noted Dr NK Arora, who is the expert chair of the National Immunization Technical Advisory Group (NTAGI). On the ongoing debate on the vaccination interval, he said the group would review the new data and make their decision based on it.

Regarding the decision to increase the gap between two doses of Covishield from four-six weeks to 12-16 weeks, he said the decision was based on a scientific decision and that there was no dissenting voice among members of the National Immunization Technical Advisory Group (NTAGI). .

“COVID-19 and 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 make the decision based on merit and wisdom. On the other hand, if it turns out that the current decision is correct, we will continue with it, ”said Arora.

Arora explained that the basis for increasing the interval between doses of vaccine was the basic scientific reason for “adenovector vaccines”. The UK Department of Health’s agency Public Health England released data during the last week of April and said that when there is a 12-week gap between doses of the vaccine, its effectiveness wanes. between 65 and 88%.

“This was the basis on which they overcame their outbreak due to the Alpha variant. The UK was able to get by because the interval they kept was 12 weeks. We also thought that it was ‘was a good idea because there are basic scientific reasons to show that when the interval is increased, the adenovector vaccines give a better response. Therefore, the decision was made on May 13 to increase the interval to 12- 16 weeks, ”he said.

“While we were aware of this data, when we had to decide on our interval, we opted for a four-week interval based on our transition test data which showed a good immune response. Later, we encountered additional scientific and laboratory data, based on which, after about six weeks, we estimated that we should increase the interval from four weeks to eight weeks, as studies have shown that the effectiveness of the vaccine is about 57% when it’s four weeks and about 60% when it’s eight weeks, he says.

On why the NTAGI did not increase the gap earlier to 12 weeks, he said: “We have decided that we should wait for the UK ground level data (the other largest user of the AstraZeneca vaccine). ” He also said there were other examples like Canada, Sri Lanka and a few other countries that use a 12-16 week interval for the AstraZeneca vaccine, which is the same as the Covishield vaccine, the statement said. .

Regarding single-dose versus two-dose protection, Arora explained how the emerging evidence and reports regarding the efficacy of partial versus full immunization were being considered by the NTAGI.

Arora referred to a study by PGI Chandigarh that compared the effectiveness of partial vaccination with full vaccination. A study by PGI Chandigarh shows very clearly that the efficacy of the vaccine was 75 percent for both partial and full vaccines. So at least in the short term, the effectiveness was similar whether you were partially or fully vaccinated. It was in connection with the Alpha variant which had swept through Punjab, northern India, and arrived in Delhi. It also meant that even if you only received one dose, you are still protected.

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