AstraZeneca vaccine far less effective against South African Covid-19 variant

The Oxford/AstraZeneca Covid-19 vaccine, of which South Africa received one million doses earlier this month, is far less effective against the 501Y.V2 variant.

The vaccine has previously been shown to have an efficacy of between 63% and 90% on two doses, but to date it was not certain how efficient it would be against new Covid-19 variants.

Financial Times has now reported the Oxford/AstraZeneca Covid-19 vaccine does not seem to protect against mild and moderate disease relayed to the new variant.

Citing a recent study, which has not been peer reviewed or published yet, Financial Times said the vaccine “showed significantly reduced efficacy against the 501Y.V2 viral variant”.

AstraZeneca confirmed the report, saying its vaccine appears to only provide limited protection against mild disease caused by the “South African variant” based on early data from a study conducted by the University of the Witwatersrand and Oxford University.

Some good news is that the vaccine is expected to protect against severe disease and death thanks to its neutralising antibody activity similar to other vaccines.

AstraZeneca said they are currently adapting the vaccine to protect against the 501Y.V2 variant and that the clinical development is expected to advance rapidly.

The Oxford/AstraZeneca Covid-19 vaccine is based on a chimpanzee adenovirus vaccine vector. This is a harmless, weakened adenovirus that usually causes the common cold in chimpanzees.

It was chosen as the most suitable vaccine technology for a Covid-19 vaccine as it has been shown to generate a strong immune response from one dose in other vaccines.

It has been genetically changed so that it is impossible for it to grow in humans. This also makes it safer to give to children, the elderly and anyone with a pre-existing condition such as diabetes.

Chimpanzee adenoviral vectors are a very well-studied vaccine type, having been used safely in thousands of subjects.