A medic administers the first dose of Covishield vaccine at a hospital in Bikaner. Photo: PTI
New Delhi: The Centre has written to states and Union Territories saying the results could be better if the second dose of the Covishield vaccine is administered 6-8 weeks after the first. Through this, the government hasn’t done away with the 28-day-gap stipulation but has increased the acceptable inter-dose gap to up to eight weeks.
The revised gap is applicable only for the Oxford-AstraZeneca vaccine, marketed as Covishield, and not for the Bharat Biotech Covaxin, for which the 4-6 week gap still applies.
The Wire Science had reported on March 10 that Indian authorities had elected to go ahead with a shorter gap in spite of a study finding better results to the contrary.
“The analysis, published in The Lancet on February 19, 2021, found Covishield’s efficacy is 55.1% when its two doses are administered less than six weeks apart but 81.3% when administered 12 weeks apart,” The Wire Science had noted. The findings had been made available via a preprint paper in early February.
Experts quoted from various new outlets in the report had said that the scale of India’s vaccination drive had necessitated the shorter gap.
A release by the Press Information Bureau has it that the government’s decision followed a meeting of the National Expert Group on Vaccine Administration for COVID-19 (NEGVAC). NEGVAC took up recommendations from the National Technical Advisory Group on Immunisation, which had revisited the time gap between two jabs, according to the PIB release.
However, official release offers a confusing picture. The first paragraph says:
“During this meeting the recommendation has been revised to provide 2nd dose of Covishield at 4-8 weeks’ interval after the 1st dose, instead of earlier practiced interval of 4-6 weeks.”
It is unclear why the government retained the possibility of second doses being administered in week 4 and week 5, even when it notes in paragraph three:
“Keeping the existing scientific evidence in view, it appears that protection is enhanced if the second dose of Covishield is administered between 6-8 weeks, but not later than stipulated period of 8 weeks.”
Union health secretary Rajesh Bhushan has also urged states and UTs to instruct the concerned officials to undertake the necessary steps to enforce the revised dosing intervals among medical workers and recipients.
The health ministry rolled out India’s countrywide vaccination drive on January 16, with healthcare workers getting inoculated first, followed by frontline workers from February 2, and those older than 60 years and older than 45 with specific comorbidities from March 1.
The communication on the revised gap came on the same day AstraZeneca announced results from a large trial in the US, Chile and Peru of the vaccine – reporting 79% efficacy at preventing symptomatic COVID-19.
Notably, the trial was able to reach its primary efficacy endpoint. This is the number of people in the study who need to get COVID-19 for the results to be able to satisfactorily answer the questions the researchers are asking. In AstraZeneca’s trial, this point was 141 cases.
The trial of the Covaxin vaccine, made by Hyderabad-based pharma giant Bharat Biotech and is the other vaccine in India’s drive, is reportedly grappling with this question.
At a time when Bharat Biotech was signing up people for Covaxin’s phase 3 trials, India was still reporting thousands of new COVID-19 case a day, giving researchers hope that they would be able to reach the trial’s primary efficacy endpoint of 130 cases within a few months.
However, the national epidemic slowed considered around December 2020 or so, and the trial is yet to have 130 COVID-19 cases. Bharat Biotech had designated some backup endpoints at the trial’s start at which its researchers would be able to announce preliminary results.
One such set of results were announced in early March, based on 43 cases against a total participation of 25,800 people. These results indicated that Covaxin has an efficacy of 80.6%. The vaccine’s final efficacy will be based on 130 COVID-19 cases in the trial, whenever that happens.
However, The Hindu reported on March 20 that experts were debating the ethics of continuing the trial at a time when the Indian government had approved both Covaxin and Covishield for restricted use but the trial continued to deny a vaccine to one half of participants.
These are the people assigned to a ‘control group’ so that researchers can compare the vaccine’s effects on the ‘vaccine group’ to a group of people who don’t receive the vaccine.
The paper quotes Anant Bhan, a bioethics researcher in Bhopal, as saying, “The [trial] participants falling in the priority groups can be requested to continue in the study for the successful completion of the trial but participants should be free to withdraw at any point of time.”
However, now that AstraZeneca’s new trial results indicate it was able to continue the trial until it reached its primary efficacy endpoint, Bharat Biotech could do so as well, instead of pausing the trial to allow some eligible participants to receive Covaxin instead of a placebo.