As omicron spreads, vaccine effectiveness against severe COVID drops slightly, WHO says

COVID-19 vaccines appear to have become slightly less effective in preventing severe disease and death as the omicron variant spreads, but they do provide "significant protection," the World Health Organization said on Tuesday.

The variant first detected in South Africa and Hong Kong last month has now been reported by 77 countries and is probably present worldwide, but should not be dismissed as "mild," WHO Director-General Tedros Adhanom Ghebreyesus said.

"Omicron is spreading at a rate we have not seen with any previous variant," Tedros told an online briefing. "Even if omicron does cause less severe disease, the sheer number of cases could once again overwhelm unprepared health systems."