The head of the World Health Organization (WHO) Monday said that the emergence of new coronavirus variants has raised major questions about the efficacy of existing Covid-19 vaccines.

WHO Director-General Tedros Adhanom Ghebreyesus comments came a day after South Africa announced it was temporarily suspending the rollout of the Oxford-AstraZeneca vaccine after a relatively small study revealed it provided reduced protection against the variant first identified in the country.

A role for the public and manufacturers

Tedros described the development as “concerning news,” though noting important caveats related to the study.

“These results are a reminder that we need to do everything we can to reduce circulation of the virus with proven public health measures," he said, speaking during WHO’s latest press briefing in Geneva.

“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," he added.

Severe illness questions

The Oxford-AstraZeneca vaccine is among several found to be effective in preventing severe disease, hospitalization and death from Covid-19, said Tedros.

The South African study showed it was minimally effective at preventing mild to moderate illness caused by the variant first identified there, known as 501Y.V2.

“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," he told journalists.