Study: CoronaVac less effective against Brazilian variant

Study: CoronaVac less effective against Brazilian variant
Health official in Espírito Santo, Brazil, holds a CoronaVac bottle. Photo: Sergio Rangel/Shutterstock

Brazilian researchers found that the Chinese-made CoronaVac vaccine may not provide sufficient protection against the new, more contagious Manaus coronavirus variant. CoronaVac doses make up the bulk of all jabs rolled out in Brazil so far.  

Researchers suggest patients may need a third dose with an updated version of the vaccine. Authors submitted the study to The Lancet magazine and await peer review.

For their research, scientists used 80 samples from patients with the Manaus Covid-19 variant, putting them in contact with plasma from patients who tested positive for Covid-19 in May — before the variant was discovered — and eight volunteers who received CoronaVac shots during clinical trials.

The immune plasma of Covid-19 convalescent blood donors had a neutralizing capacity against the Manaus variant six times lower than against the SARS-CoV-2 B-lineage. “Moreover, five months after booster immunization with CoronaVac, plasma from vaccinated individuals failed to efficiently neutralize [the Manaus variant],” reads the study.

It is believed that the Manaus variant may escape neutralizing antibodies from previous infections, “and thus, reinfection may be plausible with antigenically distinct variants with mutations in spike protein,” a finding potentially corroborated by the outbreak of reinfections in Manaus. 

The researchers warn that its sample size is small and further studies are needed to understand how exposure to other variants may boost immunization rates. Nonetheless, they believe that “updated versions [of vaccines] may be required to halt the transmission of new variants.”

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