India's health ministry on Monday wrote to states asking them to administer second AstraZeneca coronavirus vaccine doses to recipients within six to eight weeks, from the current guideline of four to six weeks.
The government said the vaccine’s protection was enhanced if the second dose of COVISHIELD is administered between 6-8 weeks.
The instruction comes in the middle of the ongoing vaccination drive in the country, as people above the age of 60 and those with illnesses above 45 with are being inoculated.
The revised interval applies only to Serum Institute of India’s Covishield – the vaccine developed by Oxford AstraZeneca and not for Bharat Biotech’s Covaxin, the Centre said.
The current gap between two doses is 28 days. Medical experts point out that it was part of the vaccine Insert that the gap between the two doses should be at least 8 weeks. Efficacy at a four-week interval was only around 50%, at eight weeks it was around 70% and at a 12-week interval it reached 80%.
Experts also point out that the trigger of the immune response improves with a gap in the time period. The difference between 6 to 8 weeks is also significant. The later, the better, they say. The Centre’s letter said it appeared that “protection was enhanced if the second dose of Covishield was administered between six and eight weeks but not later than that”.
Sources in the Health Ministry told News18 that the move had nothing to do with the government “running out of vaccines” as being reported by some outlets. They said there was no vaccine shortage and the decision was based on NTAGI and NEGVAC recommendations.
In the letter by Union Health secretary Rajesh Bhushan, he told states – “In view of the emerging scientific evidence, the interval between two doses of a specific COVID-19 vaccine, Covishield, has been revisited by the National Technical Advisory Group on Immunization (NTAGI) and subsequently by National Expert Group on Vaccine Administration for COVID-19.”
More than 4.50 crore vaccine doses have been administered across the country till date.