Covid-19: Experts vouch for mix-and-match vaccine policy

‘Update booster policy’

Indian SARS-CoV-2 Genomics Consortium (INSACOG) ex-chairperson Dr Shahid Jameel, in a statement to South First, insisted that people with vulnerabilities take the booster doses.

“India should use science to update its booster policy. The current policy is not making the best use of evidence and availability of vaccine choices,” he said.

Renowned epidemiologist and Karnataka’s Technical Advisory Committee member Dr Giridhara R Babu concurred that it was time to revise the booster policy.

He said preliminary evidence suggests that heterologous boosting, where a different vaccine is given at various stages of immunisation, results in more robust immune responses than homologous boosting, where the same vaccine is given in all the doses.

He added that it is a fact that the third dose of all approved vaccines can significantly increase one’s immunity against the virus. “So, the third dose of any approved vaccine is better than nothing,” he adds.

Alternate viewpoint

On the other hand, an epidemiologist and a member of the Covid working group of the National Technical Advisory Group (NTAGI) Dr Jayaprakash Muliyil opines that there is no need to change the booster policy.

Dr Muliyil insists that the body doesn’t care how the exposure to infection occurs —through vaccines or natural infection.

He said that when a new variant enters an immunised body, it has to face the built-in immunity and T cell memory developed due to earlier exposure.

“Booster shows antibodies going up, which means the previous infection is alive and is responding. So there is no need for the booster or mix and match of vaccines,” he said.

A senior virologist who did not want to be named said that the US regulators recently advised the vaccine makers to develop boosters targeting the latest Omicron strains BA.4 and BA.5.

However, he says, “by the time this is done, the virus would have mutated further and moved on to new variants. So, it’s better to develop a broader-acting shot that could provide long-term protection.”

India’s first heterologous booster

The Drugs Controller General of India has also approved Corbevax, a vaccine with Biological E’s protein sub-unit Covid-19, to be the country’s first heterologous booster for adults.

Studies have shown that antibodies against Omicron were neutralised in about 91 percent of the recipients of Covishield booster dose and in about 75 percent of recipients of Covaxin booster dose.

But despite the approval, the vaccine is awaiting clearance from NTAGI, the final body that evaluates vaccine data.

It can be noted that the study by Vellore’s Christian Medical College (CMC) on mixing Covishield and Covaxin has shown that taking Covishield after a dose of Covaxin has far superior results.

However, India continues to use only Covaxin as the booster dose for those who have already been vaccinated twice with the same.