WHO Director-General Tedros Adhanom Ghebreyesus.

The World Health Organization (WHO) has raised concerns after reports casting doubts on the efficacy of a coronavirus vaccine emerged.

In a statement on Tuesday, the health body said that the Oxford-AstraZeneca vaccine is one of the several that has shown to be effective in preventing severe disease, hospitalisation and death from Covid-19.

Yesterday, South Africa announced that it was putting a temporary hold on the rollout of the Oxford-AstraZeneca vaccine after a study showed it gave minimal protection against the country’s coronavirus variant.

The variant accounts for 90 per cent of new Covid-19 cases in South Africa, according to scientists.

But WHO Director-General Tedros Adhanom Ghebreyesus, has said data used in the study was from a limited sample size and the participants were younger and healthier.

“Given the limited sample size of the trial and the younger, healthier profile of the participants, it is important to determine whether or not the vaccine remains effective in preventing more severe illness,” the health body said.

WHO acknowledged that manufacturers of vaccines will have to adapt to mutations of the coronavirus so that the vaccines remain effective.

“It also seems increasingly clear that manufacturers will have to adjust to the evolution of the virus, taking into account the latest variants for future shots, including boosters,” Tedros said.