NEW DELHI: The Indian government on Monday revised the interval between two doses of Covishield vaccines to 4-8 weeks, from the existing 4-6 weeks, after evidence showed higher efficacy following a longer gap between the shots.
The union health ministry said, in view of the emerging scientific evidence, the interval between two doses of Covishield was revisited by National Technical Advisory Group on Immunisation (NTAGI) and by National Expert Group on Vaccine Administration for covid-19 (NEGVAC) in its 20th meeting this month.
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"During this meeting the recommendation has been revised to provide second dose of Covishield at 4-8 weeks’ interval after the first dose, instead of earlier practiced interval of 4-6 weeks. This decision of revised time interval between two doses is applicable only to Covishield and not to covaxin caccine," the health ministry said in a statement.
Union health secretary Rajesh Bhushan said, accordingly states have been advised to maintain an interval of 4-8 weeks before administrating the second dose of Covishield vaccine to beneficiaries.
"Keeping the existing scientific evidence in view, it appears that protection is enhanced if the second dose of Covishield is administered between 6-8 weeks, but not later than stipulated period of 8 weeks," Bhushan said.
The dosage interval of AstraZeneca vaccine, manufactured by the Serum Institute of India (SII), has been a matter of debate, and recently the World Health Organization’s (WHO) Strategic Advisory Group of Experts on Immunisation (SAGE) had said in the light of the observation that two-dose efficacy and immunogenicity increase with a longer inter-dose interval, WHO recommends an interval of 8 to 12 weeks between the doses. However, it also said that if the second dose is inadvertently administered less than 4 weeks after the first, the dose does not need to be repeated.
AstraZeneca in February had submitted clinical trial data of its vaccine, co- developed with the Oxford University, after requests by various regulators and authorities across the world.
AstraZeneca had indicated that increasing the interval between two doses will be an added advantage for India in covering more people. "There is data available for administration of the second dose up to 12 weeks after the first dose from the overseas studies," a company spokesperson had told Mint.
India started its nationwide covid-19 vaccination programme on 16 January.
According to the WHO, so far, more than 20 million doses of the AstraZeneca vaccine have been administered in Europe and more than 27 million doses of the Covishield vaccine--AstraZeneca shots produced by Serum Institute of India--have been administered in India.
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