The British drugmaker says its vaccine has shown “limited effectiveness against minor illnesses” caused by the South African variant of the coronavirus.
The COVID-19 vaccine developed by AstraZeneca and the University of Oxford appears to offer limited protection against mild illnesses caused by the South African variant of the coronavirus, said a spokesman for the British pharmaceutical company.
The statement on Saturday came after the Financial Times reported that the vaccine failed to prevent mild and moderate illnesses caused by the variant first identified in South Africa.
The newspaper cited the first data from a test conducted by the University of Witwatersrand in South Africa and the University of Oxford, whose findings are due to be published on Monday.
The FT noted that none of the more than 2,000 mostly healthy and young study participants had been hospitalized or died. The results have not yet been peer-reviewed.
Responding to the FT report, an AstraZeneca spokesman said: “In this small phase I / II trial, initial data showed limited efficacy against minor illnesses mainly due to the South African variant B.1.351.
“However, we were unable to adequately determine its effect against serious illness and hospitalization, as the subjects were predominantly healthy young adults.”
The company said it believed its vaccine could protect against serious illnesses, since the neutralizing antibody’s activity was equivalent to that of other COVID-19 vaccines that have shown protection against serious illnesses.
The spokesman also said that AstraZeneca has started to adapt its vaccine against the South African variant and “will rapidly advance in clinical development so that it is ready for delivery in the fall, if necessary”.
Although thousands of individual changes have emerged as the virus has evolved into new variants, only a small minority is likely to be important or change the virus appreciably, according to the British Medical Journal.
Among the variants of the coronavirus currently of most concern to scientists and public health specialists are the so-called “South African”, “British” and “Brazilian” variants, which appear to spread more quickly than others.
Other vaccine developers, including Johnson & Johnson and Novax, also said their vaccines have shown reduced effectiveness in clinical trials conducted in South Africa.
The Johnson & Johnson vaccine was 57 percent effective in South Africa, compared with 72 percent in the United States and 66 percent in Latin America. Novax, meanwhile, said its vaccine was 89.3 percent effective in a trial conducted in the UK, but showed only 50 percent effective in a trial conducted in South Africa.
Moderna also reported a reduced immune response from her vaccine against the South African variant, and said she would test a new booster injection targeting that variant.
Scientists say the mutations underscore the need to speed up vaccination efforts before new and even more dangerous variants emerge.