GENEVA (AP) — The head of the World Health Organization said Monday the emergence of new COVID-19 variants has raised questions about whether or not existing vaccines will work, calling it “concerning news” that the vaccines developed so far may be less effective against the variant first detected in South Africa. 

Tedros Adhanom Ghebreyesus said at a media briefing that South Africa’s decision on Sunday to suspend its vaccination campaign using the AstraZeneca vaccine is “a reminder that we need to do everything we can to reduce circulation of the virus with proven public health measures.”