Mutant variants: Whole virus vaccines better?

Mutant variants: Whole virus vaccines better?

Indian vaccine experts say that whole-virus vaccines such as Covaxin made by Bharat Biotech can work better against new variants of a virus, compared to vaccines that target only a part of the virus.

All the three major global vaccines — those from the Pfizer and BioNTech partnership, the Oxford University-AstraZeneca team and from Moderna — are based on the spike protein used by SARS-CoV-2 to enter the host cell. However, viruses can undergo mutations in the spike protein as well.

On the other hand, vaccines made from the whole virus (killed) are more likely to act against the mutant strain too, according to Dr Balram Bhargava, Director General of Indian Council of Medical Research (ICMR). ICMR, along with Pune-based National Institute of Virology, has collaborated with Bharat Biotech for developing such a vaccine.

Even if one or two points undergo mutations, the whole virus will still have many other regions to generate a response, unlike mRNA vaccines that target specific areas and may not work as well when those areas mutate, he added.

Experts, however, say this argument is still theoretical. No trial, they point out, demonstrated that a whole virus- or inactivated virus-based vaccine can be more effective than a nucleic acid vaccine to stop the attack of a mutant strain.

This was one of the considerations for the government drug regulator’s subject expert committee (SEC) as it recommended conditional approval for the ICMR-Bharat Biotech vaccine in spite of the fact that phase III safety and efficacy clinical trials have not yet been completed.

“This approval ensures India has an additional vaccine shield in its arsenal, especially against potential mutant strains in a dynamic pandemic situation — a strategic decision for our vaccine security,” tweeted India’s health minister, Harsh Vardhan.

Now ICMR researchers are testing whether antibodies found in the blood of people vaccinated with Covaxin are effective at blocking a variant that emerged in the United Kingdom, called B.1.1.7, which is now circulating in India, too. The results are expected soon.

After testing Covaxin against the B.1.1.7 variant, the ICMR will move on to investigating the vaccine made by the UK-based University of Oxford and AstraZeneca, which is being produced by Serum Institute of India in Pune, and an as-yet unapproved shot made by Zydus Cadila in Ahmedabad.

Chinese vaccine maker Sinopharm has also tested whether a specific mutation in the B.1.1.7’s spike protein could compromise their inactivated vaccine. They report that antibodies produced by vaccinated monkeys and people can neutralize the variant, and the results have been submitted for publication. The company has yet to release detailed efficacy data from clinical trials.

The other vaccine makers, Pfizer and Moderna, are also testing whether mutations in the B.1.1.7 variant and one that originated in South Africa, called 501Y.V2, weaken the performance of their vaccines. A preprint published on 7 January found that a mutation known as N501Y, which has been identified in both variants, did not alter the activity of antibodies produced by people who had been vaccinated with the Pfizer–BioNtech vaccine.

Straight Talk

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