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South African Covid variant may thwart vaccine

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A laboratory study suggests that the South African variant of the coronavirus may reduce antibody protection offered by the Pfizer-BioNTech vaccine by two-thirds, and it is not clear if the shot will be effective against the mutation, the companies said.

The study found the vaccine was still able to neutralise the virus and there is not yet evidence from human trials that the variant reduces vaccine protection, the companies said on Wednesday.

Still, they are making investments and talking to regulators about developing an updated version of their mRNA vaccine or a booster shot, if needed.

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For the study, scientists from the companies and the University of Texas Medical Branch (UTMB) developed an engineered virus that contained the same mutations carried on the spike portion of the highly contagious coronavirus variant first discovered in South Africa, known as B.1.351. The spike, used by the virus to enter human cells, is the primary target of many Covid vaccines.

Researchers tested the engineered virus against blood taken from people who had been given the vaccine, and found a two-thirds reduction in the level of neutralising antibodies compared with its effect on the most common version of the virus prevalent in trials in the United States.

Their findings were published in the New England Journal of Medicine.

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Because there is no established benchmark yet to determine what level of antibodies are needed to protect against the virus, it is unclear whether that two-thirds reduction will render the vaccine ineffective against the variant spreading around the world.

However, UTMB professor and study co-author Pei-Yong Shi said he believes the Pfizer- BioNTech vaccine will likely protect against the variant.

“We don’t know what the minimum neutralising number is. We don’t have that cutoff line,” he said, adding that he suspects the immune response observed is likely to be significantly above where it needs to be to provide protection.

That is because in clinical trials, both the Pfizer-BioNTech vaccine and a similar shot from Moderna Inc conferred some protection after a single dose with an antibody response lower than the reduced levels caused by the South African variant in the laboratory study.—Al Jazeera

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