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AstraZeneca COVID-19 Vaccine is Inefficacious Against the South Africa Variant

A 2-dose vaccination regimen did not show protection against mild-to-moderate disease due to the B.1.351 variant.

In what could be viewed as confirming previous data and reporting, the modified adenovirus-based vaccine ChAdOx1 nCoV-19 (AZD1222) produced by AstraZeneca was found to be only 10% efficacious against the B.1.351 (South Africa) variant, according to a new study.

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

“The incidence of mild-to-moderate COVID-19 more than 14 days after the second injection did not differ between placebo (81.9 per 1000 person-years) and vaccine (73.2 per 1000 person-years) recipients; vaccine efficacy was 10.6% (95% CI, −66.4 to 52.2),” the investigators reported. “...In this trial, we found that two doses of the ChAdOx1 nCoV-19 vaccine had no efficacy against the B.1.351 variant in preventing mild-to-moderate COVID-19.”

The study’s enrollment coincided with the peak of the first COVID-19 wave in South Africa, according to investigators. In the study's totality, 1010 participants received the vaccine and 1011 received the placebo. For the primary analysis, the study had a total of 1467 seronegative participants (750 assigned to the vaccine and 717 to placebo).

In terms of some positive results, there were no hospitalizations for severe COVID-19, and the vaccine has previously showed a 75% efficacy in preventing mild-to-moderate COVID-19 prior to the arrival of the B.1.351 variant.

Back in February, South Africa announced it had halted its use of the AstraZeneca vaccine and decided to begin using the Janssen Pharmaceutical Companies of Johnson & Johnson's Ad26.COV2.S COVID-19 vaccine for its front-line health care workers and will use it in a study to see what protection it offers this cohort.