The World Health Organization warns Europe faces a deadly Covid-19 surge this autumn and has urged caution as restrictions ease.
Although new cases continue to decline across the continent, and 36 countries including the U.K., France and Germany have begun easing lockdown rules, the WHO insists people must act sensibly over the summer or risk "devastating" consequences later this year.
"We've been here before. Last summer, cases gradually rose in younger age groups, then moved into older age groups, leading to a devastating... loss of life in the autumn and winter of 2020," said Hans Kluge, WHO Europe's regional director. "Let's not make that mistake again."
Experts are also warning that the Delta variant of coronavirus poses a serious risk to Europe as it is highly transmissible and could spread quickly across the region as people begin to travel more freely and socialise in groups.
"It is not yet prevalent in the European region but in some countries has already displaced the dominant Alpha variant," said Katy Smallwood, a senior emergency officer at WHO Europe.
"We've seen very significant evidence of significantly higher transmissibility, we've seen initial basis for increased risk of hospitalisation, and we've seen some evidence of immune escape, especially after only one dose of vaccine. Our assessment is that this does pose a significant risk in terms of community transmission."
WHO has launched the new campaign Summer Sense to encourage people to "enjoy the summer safely" and travel "responsibly", while also promoting the testing and tracing processes.
While Europe has made good progress in vaccinating its population, only 17 per cent have received both Covid-19 doses and so coverage is "still far from sufficient to protect the region from a resurgence" as many people over 60 remain unvaccinated and at risk.
"We are by no means out of danger," Kluge said. "If you choose to travel, do it responsibly. Be conscious of the risks. Apply common sense and don't jeopardise hard-earned gains. Wash your hands, keep a distance, choose open settings, wear a mask."
Leading virologist Christian Drosten believes cases are certain to rise after the summer holidays, adding the pandemic could become an epidemic by the autumn or winter. He believes this could continue to happen each year but the surges could be controlled by vaccine boosters.