WHO: You should still wear a mask even if you have been vaccinated

In an email to the press, WHO wrote: "Vaccines can save lives, but they alone are not enough."

The announcement came after the US Centers for Disease Control and Prevention (CDC) allowed vaccinated people to remove their masks in public. To date, 60% of adults in the country have received at least one dose of vaccine. The number of infections has fallen rapidly, with an average of 38,000 people over the past seven days, or 11 cases per 100,000 people.

WHO declined to comment specifically on the US situation, but experts stressed that the decision to lift restrictions, including mask recommendations, was based on more factors than vaccination rates.

"It depends on the extent of the virus's spread, the number of vaccines, the variants circulating...", said Maria Van Kerkhove, WHO's Covid-19 technical team leader.

A 15-year-old student receives a Covid-19 vaccine in East Hartford, USA, on May 13. Photo: NY Times

Covid-19 vaccines have been shown to be highly effective in preventing severe infection and death, and there is growing evidence that they protect people from transmitting the virus.

But the WHO's chief scientist, Soumya Swaminathan, said they were "not 100% effective." "You can get the disease without symptoms, and you can get mild or moderate disease even if you're vaccinated," she said.

She also warned that vaccines are not a panacea against the virus. "That's why we need additional protective measures like wearing masks and keeping a safe distance until countries reach herd immunity and the virus spread is at its lowest level."

She warned that so far, very few countries are in a position to completely eliminate social distancing. The director of the WHO's Health Emergencies Programme, Mike Ryan, agreed. "Restrictions or mask mandates should only be relaxed when transmission is low and vaccination coverage is high," he said.