New cases are hitting 100,000 daily in Europe. Nearly 20,000 infections were reported in Britain, while Italy, Switzerland and Russia were among nations with record case numbers.

While deaths globally have fallen to around 5,000 per day from April’s peak exceeding 7,500, WHO Chief Scientist Soumya Swaminathan said caseloads were rising in intensive care units.

“Mortality increases always lag behind increasing cases by a couple of weeks,” Swaminathan said during a WHO social media event. “We shouldn’t be complacent that death rates are coming down.”

More than 38 million people have been reported infected globally and 1.1 million have died.

Despite the global push for a COVID-19 vaccine, with dozens in clinical trials and hopes for initial inoculations this year, Swaminathan reiterated that speedy, mass shots were unlikely.

Two candidates, from Johnson & Johnson and AstraZeneca’s U.S. trial, are paused on safety concerns, while manufacturing billions of doses of an eventual successful vaccine will be a colossal challenge demanding hard decisions about who gets inoculated first.

“Most people agree, it’s starting with health care workers, and front-line workers, but even there, you need to define which of them are at highest risk, and then the elderly, and so on,” Swaminathan said.

“A healthy young person might have to wait until 2022.”

The WHO has said letting infection spread in hopes of achieving “herd immunity” is unethical and would cause unnecessary deaths. It urges hand-washing, social distancing, masks and — when unavoidable, limited and targeted restrictions on movements — to control disease spread.

“People talk about herd immunity. We should only talk about it in the context of a vaccine,” Swaminathan said. “You need to vaccinate at least 70% of people … to really break transmission.” (Reporting by John Miller and Stephanie Nebehay; Editing by Alison Williams)