Some experts are worried over move to use the same vaccine as booster dose

Some healthcare specialists, who are entitled to get precautionary vaccine doses from January 10, have expressed concern over the government's decision to use the same vaccine as the third dose. "It would probably be wiser to use a different vaccine to enhance antibody generation," said Anoop Misra, chairman, Fortis C-DOC, a Delhi-based hospital. However, he said more data is needed.

Third Dose
The third dose of the Covid-19 vaccine to be given to healthcare workers, frontline workers and those aged 60 years and above with comorbidities will be the same as that of the first two jabs, the government said on Wednesday.


According to Ambrish Mithal, chairman, endocrinology and diabetes, Max Healthcare, the government has "played safe" by sticking to the same vaccine in the absence of data regarding mixing of vaccines.

"Potentially, the best would be to use something like Covovax as a third dose. It's approved but not available yet. And we don't have access to RNA vaccines," he said. Covovax is being manufactured by Pune-based Serum Institute of India and is based on tech from Novavax.

lack of evidence

A member of National Technical Advisory Group on Immunisation (NTAGI), that held a series of meetings before the decision to give the same vaccine as a booster was taken on January 3, said that the decision was based on the fact that if vaccines are mixed reactogenicity increases. Reactogenicity refers to reactions that occur soon after vaccination.

But many experts have a different view. "Amongst the available vaccines produced in India, the best choice of booster evidence-wise would be Covovax and not the same vaccine," said AK Singh, senior consultant endocrinologist at GD Hospital and Diabetes Institute, Kolkata.

Some experts referred to a study by AIG Hospital which found that mixing of Covid-19 vaccines (Covishield and Covaxin) provides higher antibody response and is safe.

However, experts feel that more data is needed. "AIG study was small, so hard to say anything about safety, but different mixed doses give equivalent immunogenicity. More data and numbers would help. Many countries are mixing doses (with exception of mRNA users), and a few are boosting with same vaccine," Gagandeep Kang, top virologist, tweeted.

Senior epidemiologist Giridhara Babu said that in the absence of evidence of using heterologous vaccines in India, it is reasonable to continue with the same vaccine, at least for Covishield. "Based on the UK evidence, AstraZeneca has shown to be effective against hospitalization and death, even with two doses I have not seen data on Covaxin, hence can't comment on that," he said.

Dr Rajeev Jayadevan, vice-chairman of the research cell of Kerala's unit of Indian Medical Association, said clinical outcome studies are needed. "Of which there are none. All outcome studies are based on mRNA third dose which are known to temporarily increase neutralising antibodies about 28-fold."