The science behind increasing gap between Covishield doses
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The government extended the interval between two doses of Serum Institute of India’s Covishield vaccine to 12-16 weeks from four to eight weeks earlier, following a recommendation from a panel responsible for immunization.

~ What has happened?

The National Technical Advisory Group on Immunization (NTAGI) recommended increasing the interval between two doses of Covishield to 12-16 weeks from four to eight weeks earlier. However, two days later the UK government, which was earlier using a 12-week interval, reduced the gap to eight weeks amid concern about the spread of the B.1.617 variant of the virus that originated in India.

~ Why was the interval changed?

NTAGI chairperson N.K. Arora said that the interval was changed following three sets of real-world data from the UK which showed that the vaccine was 65-88% effective. The data he was referring to was published in The BMJ, a peer-reviewed medical journal run by the British Medical Association. The study was conducted between 1 December and 3 April, when the B.1.7 variant, first discovered in UK, was dominant.

There had been indications over three months back that a longer interval provided better protection. AstraZeneca's updated analysis of its UK trial in February showed that the vaccine is more effective when the interval between the two doses is longer. Vaxzevria has a higher efficacy rate for an interval of 12 weeks or more at 80%.

~ What are breakthrough infections, and is there a risk of such infections with longer intervals?

Breakthrough infections are illnesses in which a vaccinated individual becomes sick from the same illness that the vaccine is meant to prevent. Surveillance study in the BMJ gave the panel confidence to increase the dosage interval, Arora says. The panel wanted to understand the balance between putting a vaccinee at risk and benefit of better protection.

~ Are allegations of increasing dosing interval due to shortage true?

There have been allegations that the dosing interval was increased because of the current shortage of vaccines, including Covishield. Arora denies it, saying that it is not going to cut off the need for a second dose either way. “What would be the point to it? Instead of giving it a month from first dose, the second dose will have to be given three months later, but it will still have to be given," Arora said.

Dr. T●●●●z H●●●●●●i and 10 others like this5 shares
Dr. S●●●●p N●●h
Dr. S●●●●p N●●h Internal Medicine
LOL. Covering up things. By the way what' s the qualification of N K Arora
May 18, 2021Like
P●●●●●k g●●d
p●●●●●k g●●d General Medicine
Pediatrician I guess
May 20, 2021Like