The COVID-19 vaccine developed by AstraZeneca and the University of Oxford appeared to offer only limited protection against mild disease caused by the South African variant of the coronavirus, a spokesman for the British drugmaker has said.

The statement on Saturday came after the Financial Times reported that the vaccine failed to prevent mild and moderate disease caused by the variant first identified in South Africa.

The newspaper cited early data from a trial conducted by South Africa’s University of the Witwatersrand and the University of Oxford, the findings of which are due to be published on Monday.

The FT noted that none of the more than 2,000 mainly healthy and young participants in the trial had been hospitalised or died. The findings are yet to be peer-reviewed.

Responding to the FT report, an AstraZeneca spokesman said: “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.

“However, we have not been able to properly ascertain its effect against severe disease and hospitalisation given that subjects were predominantly young healthy adults.”

The company said it believed its vaccine could protect against severe disease, given that the neutralising antibody activity was equivalent to that of other COVID-19 vaccines that have demonstrated protection against severe disease.

The spokesman also said AstraZeneca has started adapting its vaccine against the South African variant and “will advance rapidly through clinical development so that it is ready for Autumn delivery should it be needed”.

While thousands of individual changes have arisen as the virus mutates into new variants, only a tiny minority are likely to be important or change the virus in an appreciable way, according to the British Medical Journal.

Among coronavirus variants currently most concerning for scientists and public health experts are the so-called “South African”, “British” and “Brazilian” variants, which appear to spread more swiftly than others.

Other vaccine developers including Johnson & Johnson and Novax have also said their vaccines showed reduced efficacy 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 United Kingdom, but only showed 50 percent effectiveness in a trial carried out in South Africa.

Moderna also reported a reduced immune response from its vaccine against the South African variant, and has said it will test a new booster shot aimed at that variant.

Scientists say the mutations underscore the need to accelerate vaccination efforts before new and even more dangerous variants arise. (AL JAZEERA AND NEWS AGENCIES)