South Africa on Sunday suspended Covid-19 vaccinations after a study showed the AstraZeneca/Oxford University inoculation failed to prevent mild and moderate cases of the virus variant that have appeared in the country.
Africa's hardest-hit nation was due to start its campaign in the coming days with a million doses of the vaccine developed by AstraZeneca and Oxford.
The study of about 2,000 people suggested the shot offered only minimal protection against mild disease of the South African variant.
"It's a temporary issue that we have to hold on AstraZeneca until we figure out these issues," Health Minister Zweli Mkhize said.
A full paper due to be published on Monday, AstraZeneca said that none of the 2,000 participants developed serious symptoms.
That could mean it would still have an effect on severe illness, although not enough data is yet available to make a definitive judgment.
Scientists said the results of the study could mean the UK’s coronavirus restrictions remain in place for longer.
UK Vaccines Minister Nadhim Zahawi urged people to remain confident in the efficacy of the AstraZeneca/Oxford vaccine.
"While it is right and necessary to prepare for the deployment of an updated vaccine, we can take confidence from the current roll out and the protection it will provide all of us against this terrible disease," he wrote in The Telegraph.
"We need to be aware that even where a vaccine has reduced efficacy in preventing infection there may still be good efficacy against severe disease, hospitalisation, and death.”
Mr Zahawi said there was likely to be a follow-up Covid-19 vaccine campaign every year.
“We see very much probably an annual or booster in the autumn and then an annual (jab), in the way we do with flu vaccinations where you look at what variant of virus is spreading around the world, rapidly produce a variant of vaccine and then begin to vaccinate and protect the nation,” he said.
Prof Sarah Gilbert, the vaccine's lead researcher, said a tweaked version of the vaccine designed to combat the South Africa variant was likely to be ready to use in the autumn. ■
Warm, dry and windy conditions, caused by the emergence of a strong cold front from the Rockies will contribute to a critical fire weather threat for parts of southeastern Colorado and southwestern Kansas this afternoon.