‘Covaxin effective against Covid-19 variants’: ICMR study
- The research, which is yet to be peer reviewed, also discovered that the vaccine is thrice as effective in creating antibodies as a previous Covid infection. To be sure, other research has shown that a previous infection does confer stronger immunity .
The indigenously developed Covaxin vaccine is effective against variants of the SARS-CoV-2 virus that causes Covid-19, including the delta variant that was first sequenced in India, a study by the Indian Council of Medical Research has found.
The research, which is yet to be peer reviewed, also discovered that the vaccine is thrice as effective in creating antibodies as a previous Covid infection. To be sure, other research has shown that a previous infection does confer stronger immunity .
The research found out that Covaxin creates 2.7 times less neutralising titre against the delta variant and three times less neutralising titre against the beta variant of the virus first reported from South Africa. The neutralising titre refers to the level of antibodies created.
But the vaccine remained effective against both strains.
“Our study demonstrated that despite a reduction in neutralisation titres with BBV152 (Covaxin) sera against B.1.351 (beta) and B.1.617.2 (delta), its neutralisation potential is well established. Lastly, the broad epitope (large number of binding sites) coverage of an inactivated vaccine decreases the magnitude of reduced neutralisation against emerging variants,” the study concluded.
Dr Pragya Yadav, senior scientist at the National Institute of Virology-Pune and the lead author of the paper, said, “Although there is a minor reduction in the neutralisation titre, it (Covaxin) will still be able to protect the vaccinated individual and eventually lessen the severity of the disease.”
Epidemiologist and vaccine expert Dr Chandrakant Lahariya said the antibody titres are not predictive of the efficacy of a vaccine. “Even if the antibody level is 1, the person is thought to be seroconverted and protected from the infection. That is what the researchers have shown: despite the reduction in antibody titres, the vaccine works,” he said.
Lahariya said that one likely impact of the lower titres could be that the antibodies might diminish sooner. “But, with Covid-19, protection against the virus is complex. Studies have shown that even after the decline in antibody levels, there is T-cell immunity. A study from the University of Washington has said that this immunity might be life-long for those who had mild infection.”
Covaxin, which was developed by Bharat Biotech in association with ICMR, is one of the three vaccines that have so far been approved for Covid-19 immunisation in India, the other two being Covishield made by Serum Institute of India and Sputnik V of Russia.
Covaxin uses an inactivated whole virus to elicit an immune response.
Covaxin accounts for at least 11% of the vaccine shots given in the country so far, according to data on the government’s CoWIN platform. The company is in the process of scaling up its production, including by licensing its technology, and is likely to contribute a higher share of immunisation in the future.