The head of the World Health Organization has again warned rich nations against administering booster shots widely, until people in poor countries have access to vaccines. WHO Director-General Tedros Adhanom Ghebreyesus said Wednesday about 20% of the world’s vaccine supply is being used for booster shots.

Tedros Adhanom Ghebreyesus: “Blanket booster programs are likely to prolong the pandemic rather than ending it, by diverting supply to countries that already have high levels of vaccination coverage, giving the virus more opportunity to spread and mutate.”