Increase Covishield dose interval to 4-8 weeks: Centre tells states

Protection enhanced if the second dose of Covishield is administered between 6-8 weeks, says Health Ministry

The government has increased the time interval between the two doses of Covishield — the Oxford-AstraZeneca vaccine against Covid-19, being manufactured locally by Serum Institute of India — from four-six weeks to four-eight weeks in view of the “emerging scientific evidence”.

The recommendation came from the National Technical Advisory Group on Immunisation, which revised its view on the issue, and subsequently by the National Expert Group on Vaccine Administration for Covid-19, the Union health ministry said on Monday.

The ministry said in a statement that keeping the existing scientific evidence in mind, it appeared that protection from the vaccine was enhanced if the second dose of Covishield was administered between six and eight weeks, but “not later than the stipulated period of eight weeks”. The revised interval was only applicable to Covishield, and not Covaxin, it clarified.

Health Secretary Rajesh Bhushan has written to all chief secretaries to ensure that states follow the revised dose interval. They have been told to instruct the officials concerned in this regard and take necessary steps to widely disseminate the message among programme managers, vaccinators, and recipients of the Covishield vaccine.
 

"This helps us to prioritise the vaccine use as we can actually give the first dose to a larger number of people faster," Praveen Gupta, director (neurology), Fortis Memorial Research Institute, said.

The technical advisory group in its interim advice had said the doses should continue to be given at a four-week interval. The group has thereafter studied extensive data including the bridging study done by Serum Institute in India on 1,600 volunteers. Last week, V K Paul, member-health, Niti Aayog, had said if there was any revision of opinion based on some changes in the data, then the government would embrace it.

Oxford-led clinical trials from the UK, Brazil, and South Africa confirmed the vaccine had 76 per cent efficacy three weeks after the first dose that is maintained to the second dose. The efficacy increased up to 82 per cent with longer inter-dose interval of at least 12 weeks or more. According to a study published in a British medical journal, the vaccine's efficacy reached 82.4 per cent after a second dose in people with a dose interval of 12 weeks or more. If the two doses were given less than six weeks apart, the efficacy was only 54.9 per cent.