Gap Between Covishield Doses Must be Reduced to 8 Weeks to Maximise Immunity: Study

The UK study, whose findings were published on May 22, found that those vaccinated with the first dose of Covishield in India were only 33 per cent protected against the symptomatic infection caused by Delta variant.

New Delhi: A lot of debate has been held surrounding the time gap between two doses of Covishield vaccine after the government increased it from 6-8 weeks to 12-16 weeks. However, a new study has suggested that the gap between the doses should be reduced again to eight weeks, citing that immunity against the Delta variant (also known as B.1.617.2) of coronavirus is developed only after the second vaccine dose.

Evidence collected from the National Centre for Disease Control and the Institute for Genomics and Integrative Biology, New Delhi, underlined that the Delta variant is “over-represented” (appearing more frequently) in post-vaccination breakthrough infections.

“B.1.617.2 is capable of creating fast-rising outbreaks with vaccination breakthroughs…We would re-emphasise that prior infections… and partial vaccination are insufficient impediments to its spread,” the NCDC-IGIB asserted.

A study published by The Lancet stated that the efficacy of all Covid vaccines against the B.1.617.2 was little to unknown, and the initial analysis has been done based on serological responses to the vaccination.

The UK study, whose findings were published on May 22, found that those vaccinated with the first dose of Covishield in India were only 33 per cent protected against the symptomatic infection caused by Delta variant, whereas those fully immunised with the second dose after three weeks showed 60 per cent protection.

The study, as per The Telegraph, highlighted that this was lower than the 50 per cent efficacy after the first dose that has been prescribed by the WHO and adopted by Indian regulatory authorities.

The UK, which was also administrating the AstraZeneca-Oxford vaccine – known as Covishield in India – cut back the interval to eight weeks

“India should consider the shorter interval between two doses because we know this variant is in wide circulation in the country,” said K Srinath Reddy, president of the Public Health Foundation of India, New Delhi, speaking to The Telegraph.

‘Delta’, the mutant virus that emerged from India, has been declared as Variant of Concern (VOC) by the World Health Organisation (WHO). The variant has triggered explosive outbreaks in India and is being closely monitored in the United Kingdom.

On May 13, India extended the wait time between the first and second doses of Covishield, manufactured by Serum Institute, to 12-16 weeks. However, the country’s vaccine advisors have been hesitant to reduce the gap alongside the UK. The current dose gap provides sufficient time for India’s population to get their first dose.

Meanwhile, the government is looking into the available evidence for the next two to three months and will reconsider the interval, if needed.

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