New Delhi: Little is known about the behaviour of the Omicron variant of the SARS-CoV-2 virus, but it is possible that as a whole virion (a complete virus particle) vaccine, Covaxin may have a better chance of being effective against it than the other, more targeted ones, a senior ICMR official has said.
Omicron, the latest variant of the virus first detected in South Africa, is believed to be its most mutated form ever.
“A lot of what we are saying about vaccines and the new variant right now is conjecture. We are assuming a lot about the structure function relationship of the virus and the vaccine. But it is a plausible conjecture to say that the virus may have less chances of escaping the immunity given by Covaxin than for other more targeted vaccines where the focus is principally on the spike protein,” Dr Samiran Panda, head of epidemiology and infectious diseases, ICMR, told ThePrint.
The mRNA vaccines, such as those of Pfizer and Moderna, are designed to produce a portion of the spike protein inside the cell by transcribing it from the codes contained in the piece of mRNA. Thus the body learns to identify the virus using that part of it. However, Omicron has about 50 mutations, many of them on the spike protein and its receptor binding domain (RBD).
“The RBD had two mutations in the Delta variant and here there are 10. If the structure of the domain changes then how well the lock and key arrangement works with other vaccines is a question. In the case of Covaxin it is a little like a Bruce Lee assault, when three different and potentially fatal sites are targeted at the same time,” Panda said.
However, he conceded that mRNA vaccines have the advantage that they can be tweaked very quickly to tailor them to variants. The AstraZeneca vaccine manufactured in India as Covishield by the Serum Institute of India also uses genetic instructions for building the virus’s spike protein to familiarise the body with the SARS-CoV-2 antigen.
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‘Seems to be more transmissible’
The World Health Organization maintains that it is not yet clear whether Omicron is more transmissible. However, Panda said that going by the rapid increase in case numbers in South Africa it does seem that it is more transmissible.
“You have to understand that all our vaccines are disease modifying and not disease preventing. I have been talking to my colleagues in South Africa and what we have come to know is that even in unvaccinated people infected with Omicron, the disease is mild. However, going by how fast cases have increased in South Africa, it does look like we are dealing with a more infectious variant,” he said.
Another senior government official, also a member of the National Expert Group on Vaccines Against Covid-19 (NEGVAC), told ThePrint that “it is possible” that Covaxin, being a whole virion vaccine, would work better against this latest variant. “Do wait for full characterisation of Omicron. We need to be sure in the laboratory as well,” he said.
Covaxin was approved with variants in mind
In January this year, when Bharat Biotech’s Covaxin was first approved by the Drug Controller General of India (DCGI), efficacy data for it was not available. However, one of the considerations that had influenced the decision was the hope that as a whole virion vaccine, it would work better against emerging variants.
“We know that the virus has undergone mutations, including in the spike protein. Pfizer has said that they will need six weeks to modify the vaccine. But because Covaxin is basically the whole virus killed, it is more likely to act against the mutant strain too. Simply put, if there are say 1,000 points in a vaccine, of which two have mutated, this (vaccine) is still going to have 998 points to generate a response, unlike others such as mRNA vaccines, which target specific areas and may not work as well when those areas mutate,” Dr Balram Bhargava, Director General, ICMR, had said then.
(Edited by Saikat Niyogi)
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