South Africa has put its rollout of the Oxford-AstraZeneca vaccine on hold after a study showed “disappointing” results against its new Covid variant.
Scientists say the variant accounts for 90% of new Covid cases in South Africa.
The trial, involving some 2,000 people, found that the vaccine offered “minimal protection” against mild and moderate cases.
But experts are hopeful that the vaccine will still be effective at preventing severe cases.
South Africa has recorded almost 1.5 million coronavirus cases and more than 46,000 deaths since the pandemic began – a higher toll than any other country on the continent.
The country has received one million doses of the Oxford-AstraZeneca jab and was preparing to start vaccinating people.
Health Minister Zweli Mkhize said his government would wait for further advice on how best to proceed with the AstraZeneca vaccine in light of the findings.
In the meantime, he said, the government would offer vaccines produced by Johnson & Johnson and Pfizer in the coming weeks.
The trial was carried out by researchers at the University of the Witwatersrand in South Africa and the UK’s Oxford University, but has not yet been peer reviewed.
The trial’s chief investigator, Prof Shabir Madhi, said it showed that “unfortunately, the AstraZeneca vaccine does not work against mild and moderate illness”.
Prof Madhi said the study had not been able to investigate the vaccine’s efficacy in preventing more serious infections, as participants had an average age of 31 and so did not represent the demographic most at risk of severe symptoms from the virus.
The vaccine’s similarity to one produced by Johnson & Johnson, which was found in a recent study to be highly effective at preventing severe disease in South Africa, suggested it would still prevent serious illness, according to Prof Madhi.
“There’s still some hope that the AstraZeneca vaccine might well perform as well as the Johnson & Johnson vaccine in a different age group demographic that I address of severe disease,” he told the BBC.
Other experts were also hopeful that the vaccine remained effective at combating more serious cases.
“What we’re seeing from other vaccine developers is that they have a reduction in efficacy against some of the variant viruses and what that is looking like is that we may not be reducing the total number of cases, but there’s still protection in that case against deaths, hospitalisations and severe disease,” Prof Sarah Gilbert, Oxford’s lead vaccine developer, told the Andrew Marr Show on Sunday.
She said developers were likely to have a modified version of the injection against the South Africa variant, also known as 501.V2 or B.1.351, later this year.
Ministers in the UK have sought to reassure the public over the effectiveness of the Oxford-AstraZeneca vaccine. Vaccines Minister Nadhim Zahawi said the injection appeared to work well against dominant variants in the UK, while Health Minister Edward Argar said there was “no evidence” the vaccine was not effective at preventing severe illness.
Early results from Moderna suggest its vaccine is still effective against the South Africa variant, while AstraZeneca has said its vaccine provides good protection against the UK variant first identified late last year.
Early results also suggest the Pfizer-BioNTech vaccine protects against the new variants.
