The move to the gap was to give flexibility to the community, since everyone cannot come at precisely 12 weeks or so, the chairman of NTAGI in a statement on Wednesday. (PTI)
The move to the gap was to give flexibility to the community, since everyone cannot come at precisely 12 weeks or so, the chairman of NTAGI in a statement on Wednesday. (PTI)

Centre defends vaccine gap amid political row

  • India’s health authorities have been under increasing pressure from experts since last month, when they expanded the gap to 12-16 weeks while the UK, whose data it cited, itself reversed the delay.
By Rhythma Kaul, New Delhi
UPDATED ON JUN 17, 2021 12:30 AM IST

The Union government on Wednesday defended its decision to keep a long gap between two doses of Covishield despite new evidence from other regions that shows second shots need to be given sooner for adequate protection from the prevalent Delta variant, although it admitted that since mid-May it has been discussing, based on the evidence, whether it needs to revert to the originally recommended 4-8 weeks gap.

India’s health authorities have been under increasing pressure from experts since last month, when they expanded the gap to 12-16 weeks while the UK, whose data it cited, itself reversed the delay. The government has been studying the suggestions and new reports suggested a group of experts did not recommend an extension beyond 12 weeks, a fact picked up by opposition leaders such as the Congress’s Rahul Gandhi.

“Decision to increase the gap between administering 2 doses of Covishield has been taken in a transparent manner based on scientific data. India has a robust mechanism to evaluate data. It’s unfortunate that such an important issue is being politicised!” said Union health minister Harsh Vardhan in a tweet, before subsequent posts in which he accused Gandhi of “mythical claims without checking any facts”.


Gandhi, while sharing a portion of a Reuters story, earlier said: “India needs quick & complete vaccination -- not BJP’s usual brand of lies & rhyming slogans to cover-up vaccine shortage caused by Modi Govt’s inaction. GOI’s constant attempts to save PM’s fake image are facilitating the virus & costing people’s lives”.

The Reuters report quoted three members of the National Technical Advisory Group on Immunisation (NTAGI) as saying that the recommendation was to extend the gap between Covishield doses to 8-12 weeks, not beyond. The Union government on May 13 set a minimum of 12 weeks and a maximum of 16 to delay the second doses, altering its earlier schedule of 6-8 weeks.

At the time, it seemed like a good idea given constraints in the supply of vaccines.

That was before the emergence of new data on the Delta variant, and the high likelihood of it being the dominant strain in the country (and responsible for the second wave) .


On May 15, the UK announced the Delta variant (B.1.617.2, seen first in India) may be more resistant to vaccines and went on to cut the delay from 12 weeks to 8 weeks for everyone above 50 the same day, and on June 15, extended this shorter dose interval to anyone over 40.

A week later, Public Health England released data of its tests on two vaccines, Pfizer/BioNTech and AstraZeneca/Oxford, that showed that one dose of the vaccine offered just a 33% protection against infection, and that two doses of the vaccine offered 88% protection in the case of the Pfizer jab and 60%, in the case of the AstraZeneca one.

Subsequent research, released earlier this week, showed that the AstraZeneca/Oxford vaccine was 71% effective in preventing hospitalisation after one dose, and 92% after both.

The AstraZeneca/Oxford shot, made in India as Covishield, accounts for nearly 90% of the 260 million vaccine doses administered in the country, where some states have curtailed vaccination programmes over supply constraints.

The head of NTAGI claimed that the decision to increase the gap was unanimous.

The move to the gap was to give flexibility to the community, since everyone cannot come at precisely 12 weeks or so, the chairman of NTAGI in a statement on Wednesday, clarifying it was a scientific decision with no dissenting voices in the expert group.

“In the last week of April, 2021, the data released by Public Health England, United Kingdom’s executive agency of the Department of Health, showed that vaccine efficacy varied between 65% - 88% when interval is 12 weeks. This 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,” said Dr NK Arora.

Indeed, research on both the Wuhan strain and the Alpha variant seemed to suggest enhanced efficiency when the gap was extended to 12 weeks.

“Hence the decision was taken on May 13, to increase the interval to 12 - 16 weeks. This also gives flexibility to the community, since everyone cannot come at precisely 12 weeks or so… We 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,” he added.

It isn’t clear why NTAGI decided to extend the gap to 16 weeks; Spain extended the gap to 16 weeks in April, but prompted by a decision to conduct tests on mixing vaccines. Canada, too, has a 16-week gap, although several states have started reducing this based on supplies (which prompted the decision in the first place).

According to the statement, the earlier (first) decision of (a) four weeks (gap) was based upon the bridging trial data available at the time, Arora added, referring to the trials carried out by Serum Institute of India, which makes Covishield.

“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,” Arora said. That change was made on March 22.

The government statement said “Canada, Sri Lanka and few other countries are also using 12-16 weeks interval for the AstraZeneca Covid-19 vaccine”.

“2-3 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% protection and two doses give about 60% protection; discussion has been going on since mid-May whether India should revert to four or eight weeks,” Arora added, according to the statement.

“Tomorrow, if the vaccine platform tells us that a narrower interval is better for our people, even if the benefit is 5% - 10%, 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,”

Explaining why NTAGI did not increase the gap to 12 weeks sooner, he said, “We decided we should wait for ground-level data from the UK (the other biggest user of AstraZeneca vaccine).”

There was no mention of vaccine supply difficulties during the month of May, when many vaccination centres across the country were shut down, in the statement.

“Part of the problem earlier was shortage of vaccine supply, but now as the supplies are improving and there is a pandemic to deal with, I would say, for Covishield, 4 weeks gap is good enough. If you are not in a hurry then you could wait for 12 weeks,” said Dr Jacob John, former head, virology department, Christian Medical College, Vellore, Tamil Nadu.




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