New Delhi: Covaxin has maintained its efficacy against B.1.617 — a SARS-CoV-2 variant that was identified in India — researchers from the Indian Council of Medical Research (ICMR), National Institute of Virology and Bharat Biotech International Ltd have found.
To determine whether the Bharat Biotech’s Covid-19 vaccine remained effective against the emerging variants of the novel coronavirus, the researchers collected blood samples of patients who had recovered from Covid along with those who had been vaccinated with Covaxin.
These samples were tested in the laboratory against a number of viral variants circulating in India — including B.1.617 and B.1.117 (variant first identified in the UK that has been found to be more transmissible than the original variant of the coronavirus).
The findings have been published in a correspondence in the journal Clinical Infectious Diseases.
How the study was conducted
The team conducted what is known as the plaque reduction neutralisation test, which is used to quantify the concentration of neutralising antibody for a virus.
In this test, the blood serum sample is diluted and mixed with a viral suspension. The mixture is then left undisturbed to allow the antibody to react with the virus.
This is then poured over a layer of host cells, usually in a petri dish. The surface of the cell layer is covered in a layer of a jelly-like substance called agar to prevent the virus from spreading.
The researchers estimate the regions of infected cells, called plaques, formed after a few days. This can be done either using microscopic observation or specific dyes that react with infected cells.
The concentration of serum to reduce the number of plaques by 50 per cent gives the measure of how much antibody is present or how effective it is.
In other words, the study did not involve clinical trials to test the efficacy of the vaccine against the emerging variants.
What the team found
In serum from 28 vaccinated individuals, the average concentration of neutralising antibodies was less when exposed to the B.1.617 variant as compared to the B.1 and B.1.117 variants.
However, in the study the researchers say the neutralising antibodies levels were still high enough to maintain the efficacy of Covaxin.
For comparison, the researchers used serum samples collected from 17 people who had recovered from Covid. The team found that the levels of neutralising antibodies were higher in those who had been vaccinated for all variants as compared to those who had recovered from Covid.
What experts say on tests
While the results from the study are encouraging, experts said that without data from Phase III clinical trials, the findings are of little consequence in the real world.
While Covaxin was rolled out to Indians in January, the team is yet to publish results from the Phase III clinical trials for the vaccine.
“One cannot tie an efficacy number or effectiveness percentage to how neutralising studies were performed in a lab. There’s no direct and clear correlation established between lab experiments and clinical efficacy yet,” Anirban Mahapatra, US-based microbiologist, told ThePrint.
Soumyadeep Bhaumik, a public health specialist at George Institute for Global Health in New Delhi, explained that public health decisions are all about striking the correct balance between risks and benefits.
“For example, we know that the virus is very deadly for the elderly. If the risk of the serious side effects is lower than the risk of death, then it is deemed feasible to vaccinate the individual,” Bhaumik said. “However, for the younger population — which is not at high risk — we need to ensure that the risk of such adverse events is not worse than the risk of the disease.”
Bhaumik noted that this is why the data from clinical trials were needed. He also said that laboratory studies, though an important first step, aren’t enough to understand the real world efficacy of the vaccines.
The ICMR-Bharat Biotech team said that the study to understand the clinical efficacy of the vaccine against variants is underway.