New Delhi: The Russian-made Sputnik V vaccine is about six times less effective against the Beta variant of SARS-CoV-2 than the original strain, a new study has found.
Published Monday in the Nature Communications journal, the study suggests that it could be necessary to update vaccines to tackle emerging variants.
Researchers from the US and Argentina collected blood samples from people who received both doses of Sputnik V, and tested the ability of the samples to neutralise different variants of the virus.
The team noted that while the Alpha (B.1.1.7) variant shows enhanced transmissibility and severe disease, it does not appear to be consistently resistant to neutralising responses elicited by the vaccines or natural infection.
They further said that the most concerning variants are those with multiple mutations in the receptor binding domain (RBD) — which helps the virus gain entry into host cells — that give it enhanced affinity for the ACE2 receptor (the protein that provides an entry point to the virus) and ability to escape neutralising antibody response.
These include the Beta (B.1.351) and Gamma (P.1) variants, which have three common mutations in the RBD — K417N/T, E484K and N501Y.
Vaccines have shown a reduction in their neutralising activity against the Beta variant, which was first identified in South Africa, in earlier studies as well.
The study authors cited past research and said that the blood samples from AstraZeneca vaccine recipients in South Africa exhibited up to 32.5-fold reduction in neutralising activity against B.1.351.
Even recipients of Moderna and Pfizer vaccines showed a similar, albeit smaller, reduction in neutralisation at 6.5-fold and 8.6-fold, respectively.
The latest study, meanwhile, revealed that for recipients of the Sputnik vaccine in Argentina, the neutralising antibody response was 6.1 times less against the Beta variant.
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Reduced response to E484K mutation
Another significant finding of the study is the 2.8-fold reduction in Sputnik’s response to the E484K mutation.
The E484K mutation is present in B.1.351 and P.1 and many other lineages, which were first detected in South America, such as the Zeta (P.2) variant. The E484K mutation is the only RBD mutation in P.2.
The researchers noted that it was surprising that the mutation alone could confer such a significant degree of resistance to the antibody response of the vaccine.
However, they added, data suggests higher levels of antibodies can overcome the resistance.
But this is not the case with B.1.351, which can resist neutralisation even with higher antibody levels because of its multiple mutations.
According to the study, other emerging variants like B.1.617 (parent lineage of Delta and Kappa variants) also have RBD mutations L452R and E484K/Q that could confer a degree of neutralisation resistance.
However, it added, that laboratory tests measuring neutralisation ability does not always translate to real world efficacy of the vaccine.
Studies have shown that all vaccines are effective against most variants, the researchers said, adding that the Sputnik vaccine is likely to retain strong efficacy at preventing severe Covid-19, even among emerging variants of concern.
However, the study raises concerns about the potential of the Beta variant and the E484K mutation to escape vaccine-elicited antibodies.
“Given the crucial roles neutralizing antibodies play in preventing infection, our results suggest that updated SARS-CoV-2 vaccines may be necessary to eliminate the virus,” the study said.
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