The study from South Africa's University of the Witwatersrand and Oxford University showed the vaccine had significantly reduced efficacy against the South African variant, according to a Financial Times report published earlier in the day.
"In this small phase I/II trial, early data has shown limited efficacy against mild disease primarily due to the B.1.351 South African variant," an AstraZeneca spokesman said in response to the FT report."However, we have not been able to properly ascertain its effect against severe disease and hospitalization given that subjects were predominantly young healthy adults," the AstraZeneca spokesman said.
The trial, which involved 2,026 people of whom half formed the placebo group, has not been peer-reviewed, the FT said.