Why did India increase Covishield dose gap while the UK reduced it?

The Centre recently increased the gap between the doses of Covishield to 12-16 weeks for the second time in 3 months. Before this, the government had increased the gap from 28 days to 6-8 weeks in March saying that the step would give better results. The recent change was done based on the recommendations of the National Technical Advisory Group on Immunisation in India (NTAGI) which fulfils a need for informing decision-making concerning the introduction of new vaccines and strengthening the Universal Immunisation Programme (UIP).

Reason for change in India

The revision in the duration between the Covishield doses in India was based on the real-world data from the UK, said NTAGI chairperson NK Arora. Data published in The BMJ– a peer-reviewed medical journal run by the British Medical Association, showed that infections fell by 65% after the first dose of either AstraZeneca or Pfizer vaccine, and researchers also found no evidence that the two vaccines differed in their ability to reduce infection rates. Apart from this, an expert panel of the World Health Organisation in February had recommended an 8-12 week interval between two doses of AstraZeneca after clinical trials found that vaccines 4-6 weeks apart had around 54% efficacy compared to 79% if the gap was 12 weeks. The data was also supported by The Lancet in March, claiming that the Oxford-AstraZeneca vaccine (also known as Covishield in India) can provide 81.3 per cent efficacy if doses are administered at 12 weeks apart.

The thing that puzzled people more was the UK government’s decision to shorten that window to 8 weeks from 12 weeks, citing concerns over the fast-spreading B.1.617 variant, informally known as the “Indian variant”. The UK government’s decision came shortly after India’s revision of the duration between jabs.

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Reason for change in the UK

Giving reasons for the revision in duration between jabs, British Prime Minister Boris Johnson said, “We have seen larger clusters of the B.1.617 variant first observed in India since last Monday. We believe this variant is more transmissible than the previous one. But we don’t know by how much. We will accelerate vaccination to those over 50 and those who are clinically vulnerable right across the country so that doses come 8 weeks after the first dose.” 

The National Health Service (NHS) had also tweeted about reducing the duration between the jabs saying, “Today the government said Covid vaccine second dose appointments will be brought forward from 12 to 8 weeks. People should continue to attend appointments and don’t need to contact the NHS. Those who should move their appointment forward will be told when they are able to do so.”

Was the decision taken in India due to a shortage of vaccines?

There is a parallel narrative alleging that India’s decision to increase the duration between jabs is due to the shortage of vaccines in the country. There are allegations that if the Centre believed in the scientific data from the UK, why was it late in implementing the same?

Responding to the allegations, V.K. Paul, Chairman, National Expert Group on Vaccine Administration for COVID-19 said, “The standard protocol of vaccine administration is 4-6 weeks. When the U.K. decided to delay their second dose, there was little scientific evidence to justify it at that time. That’s why our own recommendation was first 4-6 weeks and based on newer evidence, it was increased to 6-8 weeks. However, evidence from there has shown that their decision to delay the second dose up to three months has seen 65%-85% protection against severe disease. Also, there was a definite break in transmission of the disease. So that’s the evidence considered by the committee to expand the dosage interval.”

The government had announced that it would vaccinate the country’s largest demographic group (people aged 18-44) from May 1 but several states notified that there is a vaccine shortage while some halted the vaccination drive for the demographic group. In this situation, the decision of increasing the gap between vaccine doses will definitely buy some time to fix the shortage.

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