Covishield and Covaxin both induce an immune system response against the B.1.617 variant but produce only half the number of antibodies, an early research by the Indian Council of Medical Research (ICMR) has found.
The variant, first identified in India, with critical mutations that make it more infectious and elusive to the immune system, has been a driving force in India’s unprecedented second Covid-19 wave, sparking fears that existing vaccines may not be as effective against it. The reports authored by scientists at the ICMR-National Institute of Virology, Pune, indicate a reduction in antibodies but scientists say the vaccines still provide protection.
The scientists found that when the B.1.617 was tested against the blood serum of someone with two doses of Covaxin, it produced 55% fewer antibodies than those stimulated against the B1 variant that had become the dominant strain in India last April. The results were roughly the same for Covishield.
When antibody levels were compared with the variant that emerged out of the United Kingdom, there was only a 6% drop, whereas against the Brazilian strain, they reduced by a half.
However, scientists have allayed fears over vaccines’ reduced effectiveness against the variant, saying protection against the variant does not solely depend on the number of antibodies they produce but also on the generation of T cells, a type of white blood cells that launch a far more specific attack against the virus.
“The antibody tests don't account for the T-cell response,” Samiran Panda told The Hindu. “Moreover, these tests were done on a very small number of individuals. The average level of antibodies don't always capture the true range of antibody production.”
International scientific opinion on the vaccines’ potency against the variant is split, with some medical experts more willing to err on the side of caution. Professor Anthony Harnden, who advises the United Kingdom government on vaccinations, told the BBC that existing vaccines were likely less effective against the variant but there was no evidence so far of more severe illness or that the variant had evaded the vaccine.