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ChAdOx1 nCoV-19 Vaccine Does Not Protect Against B.1.351 SARS-CoV-2 Variant

THURSDAY, March 18, 2021 -- A two-dose regimen of the ChAdOx1 nCoV-19 vaccine does not seem to protect against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.351 variant, first identified in South Africa, according to a study published online March 16 in the New England Journal of Medicine.

Shabir A. Madhi, Ph.D., from the University of the Witwatersrand in Johannesburg, South Africa, and colleagues enrolled 2,026 HIV-negative adults in a randomized trial to examine the safety and efficacy of the ChAdOx1 nCoV-19 vaccine in South Africa. Participants were randomly assigned to receive either two doses of vaccine or placebo 21 to 35 days apart (1,011 and 1,010 participants, respectively).

The researchers found that both the pseudovirus and live-virus neutralization assays showed greater resistance to the B.1.351 variant in serum samples obtained from vaccine versus placebo recipients. Mild-to-moderate COVID-19 developed in 3.2 and 2.5 percent of placebo and vaccine recipients, respectively, for an efficacy of 21.9 percent (95 percent confidence interval, −49.9 to 59.8 percent). Among the 42 cases with COVID-19, 92.9 percent were caused by the B.1.351 variant; vaccine efficacy was 10.4 percent (95 percent confidence interval, −76.8 to 54.8) against this variant.

"Deliberations on the utility of the ChAdOx1 nCoV-19 vaccine also need to be made in the context of ongoing global spread and community transmission of the B.1.351 variant and the evolution of other SARS-CoV-2 lineages that include similar mutations," the authors write.

Several biopharmaceutical companies were involved in manufacturing and production of the ChAdOx1 nCoV-19 vaccine; production was funded by AstraZeneca. Several authors disclosed ties to the pharmaceutical industry, including AstraZeneca. Two authors have patents pending for SARS-CoV-2 vaccines.

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