The health ministry asserted that discussions are underway whether India should revert to four or eight weeks interval for Covishield vaccine and the emerging evidence regarding efficacy of partial versus full immunisation is also being considered.
“India has a robust mechanism to evaluate data. Decision to increase the gap between administering 2 doses of Covishield has been taken in a transparent manner based on scientific data,” Harsh Vardhan said on Twitter.
Decision to increase the gap between administering 2 doses of #COVISHIELD has been taken in a transparent manner ba… https://t.co/LYUXgIh6GL
— Dr Harsh Vardhan (@drharshvardhan) 1623822974000
Clarifying government’s stand on increasing the gap between Covishield doses, chairman of India’s Covid-19 working group of NTAGI, Dr NK, Arora said the decision was taken “scientifically, giving paramount importance to health and protection of the community.”
“The Covid Working Group took that decision, with no dissenting voice. This issue was then discussed threadbare at an NTAGI meeting, again with no dissenting notes. The recommendation was that the vaccine interval has to be 12 – 16 weeks,” he asserted.
#LargestVaccinationDriveNTAGI Chair Dr N K Arora: Decision regarding enhancing interval between two doses of… https://t.co/nWDe9FMqlr
— Ministry of Health (@MoHFW_INDIA) 1623774895000
Dr Arora said that the earlier decision of four weeks was based upon the bridging trial data available then. He also cited that the increase in gap between two doses was based on studies that showed higher efficacy with increase in gap.
“Initial studies on Covishield were very heterogeneous. Some countries like the UK went for a dose interval of 12 weeks when they introduced the vaccine, in December 2020. While we were privy to this data, when we had to decide our interval, we went for four weeks interval based on our bridging trial data which showed good immune response,” he said.
“Later we came across additional scientific and laboratory data, based on which after six weeks or so, we felt we should increase the interval from four weeks to eight weeks, since studies showed that vaccine efficacy is about 57% when it is four weeks and about 60% when it is eight weeks,” he added.
Speaking about why the NTAGI did not increase the gap earlier to 12 weeks, he said, “We decided we should wait for ground-level data from the UK (the other biggest user of AstraZeneca vaccine).”
He also said that there were other examples like Canada, Sri Lanka and few other countries which are using 12-16 weeks interval for AstraZeneca vaccine which is the same as Covishield vaccine.