AZ Vaccine Doesn’t Protect Against Mild-to-Moderate COVID-19 Infection From South African Variant

In another blow to AstraZeneca’s (AZ) COVID-19 vaccine, a peer-reviewed study has found that it failed to protect against mild-to-moderate infections caused by the virus’ South African variant.

Researchers from AZ, the University of Oxford, the University College London and other organizations conducted a phase 1b/2 trial in South Africa involving 2,021 participants, with approximately half getting at least one dose of the vaccine and the other half getting a placebo.

The study, published in the New England Journal of Medicine, found that mild-to-moderate COVID-19 developed in 23 placebo recipients (3.2 percent) and 19 vaccine recipients (2.5 percent). Among the 42 participants who contracted the virus, nearly all of the cases (39) were caused by the South African variant, and the researchers calculated that the vaccine’s efficacy against the variant was a dismal 10.4 percent.

“In this trial, we found that two doses of the [AZ] vaccine had no efficacy against the B.1.351 variant in preventing mild-to-moderate COVID-19,” the researchers said. “The lack of efficacy against the B.1.351 variant should be considered in the context of the 75 percent efficacy in preventing mild-to-moderate COVID-19 with onset at least 14 days after even a single dose … that was observed before the B.1.351 variant emerged in South Africa.”

Although none of the infected participants progressed to hospitalization or death, Shabir Madhi, leader of the trial in South Africa, said that the study’s findings make a strong argument for revamping vaccines to protect against mutations.

“Despite the disappointing finding that the AZ vaccine did not protect against mild COVID infection because of the [South African variant], peer review and publication of our research validates the findings and makes a compelling case for the development of second-generation vaccines worldwide," he said.

More than a dozen European countries have halted inoculations with the AZ vaccine after blood clots were reported in some vaccinated patients (DID, March 16). Although the European Medicines Agency (EMA), the World Health Organization (WHO) and the company itself have concluded it is highly unlikely the vaccine caused the safety issues, the EMA will hold an emergency meeting today to formally issue a determination.

Despite its apparent lack of protection against the South African strain, Madhi praised the vaccine, noting that it could still help prevent hospitalization or death in high-risk patients with co-morbidities and called it “essential in the arsenal against this virus.”

Read the study findings here: bit.ly/3tnoc1s. — James Miessler