The WHO lacks sufficient scientific data to condone the widespread use of boosters, Director-General Tedros Adhanom Ghebreyesus said at a press briefing Tuesday. The organization has worked to address vaccine inequities since last winter, asking world leaders on Wednesday to impose a moratorium on third doses through the end of the year to redirect surplus vaccines to low-income nations.

“There are countries with less than 2% vaccination coverage, most of them in Africa, who are not even getting their first and second dose” Tedros said. “And starting with boosters, especially giving it to healthy populations, is really not right.”

In Africa, just under 3.5% of the eligible population is fully vaccinated, WHO officials said. The organization reiterated its approval for the administration of booster doses for the immunocompromised, but said Africa was on track to miss the director-general’s goal of a 10% vaccination rate in every country by the end of the year.