Covishield dose interval under discussion: NTAGI working group chairman

Discussions are underway on whether India should have a four or eight weeks interval for Covishield vaccine Chairman of Indias Covid19 Working Group of NTAGI Dr N K Arora saidHe also said that the emerging evidence and reports regarding efficacy of partial versus full immunisation are also under considerationOn the decision to increase the gap between two doses of Covishield from foursix weeks to 1216 weeks he said the move was based on scientific decision and there was no dissenting voice among the National Technical Advisory Group on Immunisation NTAGI membersCOVID19 and the vaccination are very dynamic Tomorrow if the vaccine platform tells us that a narrower interval is better for our people even if the benefit is 51037 the Committee will take the decision on the basis of merit and its wisdom On the other hand if it turns out that the current decision is fine we will continue with it Arora saidThe decision to increase the gap lay in the fundamental scientific reason regarding behaviour of adenovector vaccines a Health Ministry statement quoted him as telling DD NewsIn the last week of April the data released by Public Health England United Kingdomrsquos executive agency of the Department of Health showed that vaccine efficacy varied between 65 and 88 per cent when interval is 12 weeksThis was the basis on which they overcame their epidemic outbreak due to the Alpha variant The UK was able to come out of it because the interval they kept was 12 weeks We also thought that this is a good idea since there are fundamental scientific reasons to show that when interval is increased adenovector vaccines give better response Hence the decision was taken on May 13 to increase the interval to 1216 weeks he saidThis also gives flexibility to the community since everyone cannot come at precisely 12 weeks or so he addedldquoWe have a very open and transparent system where decisions are taken on scientific basis 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 1216 weeks he saidDr Arora said the earlier decision of four weeks was based on 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 gapInitial 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 he saidWhile 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 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 per cent when it is four weeks and about 6037 when it is eight weeksrdquo he saidOn why the NTAGI did not increase the gap earlier to 12 weeks he said ldquoWe decided we should wait for groundlevel data from the UK the other biggest user of AstraZeneca vaccinerdquoHe also said that there were other examples like Canada Sri Lanka and few other countries which are using 1216 weeks interval for AstraZeneca vaccine which is the same as Covishield vaccine the statement saidOn the protection from single dose versus two doses Dr Arora explained how emerging evidence and reports regarding efficacy of partial versus full immunization were being considered by NTAGIldquoTwothree days after we took the decision to increase the dosage interval there were reports from UK that single dose of AstraZeneca vaccine gives only 33 per cent protection and two doses give about 60 per cent protection discussion has been going on since midMay whether India should revert to four or eight weeks he saidHe also said that it was decided to establish a tracking platform to assess the impact of the vaccination programmeWhen NTAGI took this decision we also decided that India will establish a vaccine tracking platform to assess not only the impact of vaccination programme but also type of vaccine and interval between doses and what happens when someone is fully partially immunized This is very important in India since around 1718 crore people have received only one dose while around 4 crore people have received two dosesrdquo he saidDr Arora referred to a study by PGI Chandigarh which compared effectiveness of partial versus full immnunisationA PGI Chandigarh study very clearly shows that vaccine effectiveness was 75 per cent for both partially immunised and fully immunized So at least in the short run effectiveness was similar whether you are partially or fully vaccinated This was in relation to the Alpha variant which had swept Punjab Northern India and came to Delhi This also meant that even if you received only one dose still you are protectedrdquoResults from the CMC Vellore study are similar he saysldquoFew days back another very important study by CMC Vellore Tamil Nadu which covers most of the current epidemic wave India experienced in April and May 2021 shows that if somebody is partially immunised vaccine effectiveness of Covishield is 6137 and with two doses the effectiveness is 6537 and there is very little difference especially since there is some degree of uncertainty involved in these calculationsrdquo he saidDr Arora said that besides PGI and CMC Vellore studies two other studies are coming up from two different organizations within DelhildquoAnd both these studies show that breakthrough infection with one dose is around 4 per cent and around 5 per cent with two doses basically hardly any difference And the other study shows that 15 2 per cent breakthrough infectionsrdquo he saidThis story has been sourced from a third party syndicated feed agencies Midday accepts no responsibility or liability for its dependability trustworthiness reliability and data of the text Midday managementmiddaycom reserves the sole right to alter delete or remove without notice the content in its absolute discretion for any reason whatsoever