GENEVA, Switzerland - The World Health Organization on Wednesday urged "extreme caution" for countries considering lifting COVID-19 restrictions, warning that high vaccination rates would not stop transmission of the virus increasing.

The UN health agency urged governments not to squander hard-won gains and return to scenes of overwhelmed hospitals and exhausted health workers.

Asked about England's plans to ditch most of its coronavirus restrictions from July 19, WHO emergencies director Michael Ryan said: "I would urge extreme caution in the complete lifting of public health and social measures at this time, because there are consequences for that."

WHO figures show that globally, after a decline in newly reported cases for seven consecutive weeks, there was a slight increase in new cases in the past two weeks.

Cases jumped 30 percent in the WHO's European region over the past week.

European countries have administered 70 vaccine doses per 100 inhabitants, according to AFP figures.

"Making assumptions that transmission will not increase because we're opening up, because of vaccine, is a false assumption," said Ryan.

"Transmission will increase when you open up, because we don't have vaccines in everybody... and we're still not sure to what extent vaccination protects against the ability to be infected or have onward transmission.

"With increased transmission in the community, we then put our most vulnerable at risk again."

- 'Open up very carefully' -
British Prime Minister Boris Johnson on Monday revealed plans to lift most of England's legal coronavirus restrictions, including face masks and social distancing, urging personal responsibility rather than government edict.

Ryan stressed he did not want to comment on specific countries, but said: "The idea that everyone is protected... and everything goes back to normal, I think right now is a very dangerous assumption anywhere in the world."

And that included Europe, where "we've seen wave after wave of cases," he said.

"We would ask governments to be really careful at this moment not to lose the gains we've made. To open up very carefully.

"I would hope that in the European environment we won't see a return to the overwhelmed hospitals and the exhausted health workers. But that's not a given."

Ryan said countries lifting restrictions needed to follow the data and give themselves the option of rowing back if it resulted in negative consequences.

Opening up with low vaccine coverage and variants circulating "is a real toxic mixture for your hospitals filling up again, and this is something that must absolutely be avoided", he added.

Ryan flatly rejected the notion that it would be better to lift restrictions and risk triggering a fresh wave of infections in the summer than doing so in the winter months.

"The logic of more people being infected is better, is, I think, logic that has proven its moral emptiness and its epidemiologic stupidity," he said.