Scientists are calling for a rethink of the goals of Covid-19 vaccination programmes, saying that herd immunity through vaccination is unlikely to be possible because of the emergence of variants like that in South Africa.

This comes as South Africa which already has one million doses of the AstraZeneca jab and was due to start vaccinating people next week has put its roll-out of the same vaccine on hold after a study showed "disappointing" results against its new Covid variant.

It is reported that the study, which involved around 2,000 people found that the vaccine offered minimal protection against mild and moderate cases of Covid-19.

The University of Oxford and AstraZeneca acknowledged that their vaccine will not protect people against mild to moderate Covid illness caused by the South African variant. 

The findings came from their study followed results from two vaccines, from Novavax and Janssen, which were trialled there in recent months and were found to have much reduced protection against the variant – at about 60%. 

According to reports, Pfizer/BioNTech and Moderna have also said the variant affects the efficacy of their vaccines, although on the basis of lab studies only.

On Sunday, South Africa's Health Minister Zweli Mkhize told an online news conference that his government will wait for further advice on how best to proceed with the Oxford-AstraZeneca vaccine in light of the new findings. 

South Africa was planning to give the AstraZeneca jab to healthcare workers but it now intends to offer them alternative vaccines from Pfizer and Johnson & Johnson (J&J) in the coming weeks.

Mkhize said: "The AstraZeneca vaccine will remain with us, up until the scientists give us clear indications as to what we need to do."

Shabir Madhi, professor of vaccinology at the University of the Witwatersrand who has been chief investigator on a number of vaccine trials in South Africa, is quoted as saying it was time to rethink the goals of mass Covid vaccination.

"These findings recalibrate thinking about how to approach the pandemic virus and shift the focus from the goal of herd immunity against transmission to the protection of all at-risk individuals in the population against severe disease,” he said.

But Prof Andrew Pollard, chief investigator on the Oxford vaccine trial, emphasised the value of the vaccines in reducing the burden on health systems.

"This study confirms that the pandemic coronavirus will find ways to continue to spread in vaccinated populations, as expected, but, taken with the promising results from other studies in South Africa using a similar viral vector, vaccines may continue to ease the toll on health care systems by preventing severe disease,” he said.

Sarah Gilbert, professor of vaccinology at Oxford, said: "We may not be reducing the total number of cases but there’s still protection in that case against deaths, hospitalisations and severe disease,” she said.

"That’s really important for healthcare systems, even if we are having mild and asymptomatic infections. To prevent people going into hospital with Covid would have a major effect.”

Ravi Gupta, professor of clinical microbiology at the University of Cambridge, said that it was pragmatic to adopt the approach that vaccines will prevent severe disease and death rather than enabling herd immunity in countries like South Africa. 

To stop transmission – if it were possible – would mean delivering huge numbers of vaccine doses, which are not working so well, very rapidly.

"We probably need to switch to protecting the vulnerable, with the best vaccines we have which, although they don’t stop infection, they probably do stop you dying,” he said.