Covid-19: Centre panel to study mixing doses, Covishield single shot

Experts welcome the news but have reservations about testing a single-dose Covishield regimen.

Government scientists will study various combinations of doses for coronavirus vaccines to see if the use of a different brands leads to better efficacy and look at how well they work if given only in a single dose or even as a shot after the booster dose to further aid the immunity of fully vaccinated people, a top official said on Monday.

An elderly woman gets inoculated against Covid, at a vaccination centre in Mumbai on Monday. (ANI Photo)

The vaccines India uses at present have a two-dose regimen. Similar studies have been carried out in other countries but independent experts said the one-dose approach, particularly for Covishield, should be made with caution since current evidence suggests it may not provide adequate protection.

“We will be looking at the feasibility of testing two dose Covid-19 vaccine regimen but with different vaccines, for which testing may start in few weeks. Dosing interval will also be examined, that includes whether a single dose or a dose followed by a booster shot or so on works better, said Dr NK Arora, chairman, Covid-19 working group, National Technical Advisory Group on Immunisation (NTAGI), Delhi.

Arora said the exercise could be expanded to other vaccines like Covaxin or Zydus Cadilla’s ZyCov-D, which is in the trials phase at present. “The idea is to study and find the most appropriate dosing interval that provides maximum protection with the number of variants circulating around,” Arora said, adding that a single dose could be worked out too, “but that’s definitely not the only focus”.

“Different type of beneficiary mix is currently available for us to examine in the form of what is called is the real-world data,” he added.

Vaccine experts have welcomed the news but have reservations about testing a single-dose Covishield regimen. “For mixed doses testing, it is a good move. But for the single dose testing, it should not be tried outside a very careful evaluation where people can be closely monitored, and sequencing can be done quickly. I am encouraged by the Johnson & Johnson vaccine but wary of the B1.617.2 virus variant,” said Dr Gagandeep Kang, physician-scientist at Christian Medical College, Vellore.

Recently, about 20 people in Uttar Pradesh’s Siddharth Nagar district were accidentally given Covaxin shots as second dose after being given Covishield jabs. Experts have been following up with them, and so far, there seem to be no safety concerns.

In the UK, an analysis of infections among people infected with the Delta variant, which was first found in India, showed a sharp drop in vaccine efficacy. The reduction was particularly stark among groups that had only one shot of Oxford-AstraZeneca (the same as Covishield) or Pfizer dose.

A single dose of either vaccine, this data suggested, led to a mere 30% protection, down from 60% efficacy after two doses of AstraZeneca and 80% efficacy after two shots of the Pfizer vaccine.

Dr Arora said that the county will have 200-300 million vaccines per month in the coming weeks as vaccine manufacturers are ramping up production. “By the end of July, we will have 200 million doses per month, and from August, we should get overall 250-300 million doses per month that would give us the capacity to inoculate close to 10 million people a day,” he said.

The Union health ministry has said that efforts are on to increase the production capacity of Covaxin to 60-70 million vaccines in July-August. By September, the country expects to produce nearly 100 million doses a day of Covaxin.

Production of Covishield that comprises almost 90% of the jabs given under the national Covid-19 immunisation programme so far is also being ramped up.

Serum Institute of India’s chief executive officer, Adar Poonawalla, had said earlier that the monthly output will be raised to 100-120 million Covishield vaccines by July-August.

SII locally manufactures Oxford-AstraZeneca vaccine under the brand name Covishield. Covaxin, on the other hand, is co-developed by Bharat Biotech and Indian Council of Medical Research.