The U.N. health agency said there were 4.5 million new COVID-19 cases reported last week, a 16% drop from the previous week. Deaths were also down by 13%, with about 13,500 fatalities. WHO said COVID-19 infections dropped everywhere in the world while deaths decreased everywhere except for Southeast Asia, where they climbed by 15% and in the Western Pacific, where they rose by 3%.

WHO Director-General Tedros Adhanom Ghebreyesus warned that with the coming onset of winter in the Northern Hemisphere and the possible emergence of a more dangerous new COVID-19 variant, experts expect to see a spike in hospitalizations and deaths. Tedros said vaccination rates, even in rich countries, were still too low, noting that 30% of health workers and 20% of older people remain unimmunized.

“These vaccination gaps pose a risk to all of us,” he said. “Please get vaccinated if you are not and a booster if it’s recommended that you have one.”

In the U.S., the Food and Drug Administration cleared its first update to COVID-19 vaccines on Wednesday, booster doses that target today’s most common omicron strain. Authorities said shots could begin within days.

Until now, COVID-19 vaccines have targeted the original coronavirus strain, even as wildly different mutants emerged. The new U.S. boosters are combination, or “bivalent,” shots. They contain half that original vaccine recipe and half protection against the newest omicron versions, called BA.4 and BA.5, which are considered the most contagious yet.

Earlier this month, Britain decided it would offer adults 50 and over a different booster option from Moderna, a combo shot targeting that initial BA.1 omicron strain.

On Friday, the European Medicines Agency will consider whether to authorize the combination COVID-19 vaccine including BA.1 made by Pfizer-BioNTech and Moderna. Another version of the Pfizer-BioNTech vaccine incorporating the BA.5 subvariant of omicron is also under review by the EU regulator.