WHO Regional Director for Europe Hans Kluge said that vaccination rates in Europe have plateaued and the region is seeing a fourth wave, The Hill reported.
"The basic principle is, if there is a situation where the peak is accelerating, don't wait" to bring back antivirus measures, and "the earlier, the stricter, the better," Kluge told CBS News.
"There's a relaxation of the public health and social measures, which is a cocktail for what we see: a fourth wave," he said in a statement.
The WHO had said in a statement Thursday that Europe could see half a million people die from COVID-19 by February next year.
The WHO has pointed out that Europe is the only region globally that saw an increase in new coronavirus cases last month, and hospitalization rates across the continents have doubled.
The statement added that in Europe only 47 percent of people have been fully vaccinated against COVID-19 and only eight of its countries have more than a 70 percent vaccination rate, with two still below 10 percent.
"Most people hospitalized and dying from COVID-19 today are not fully vaccinated," Kluge said.
The US, meanwhile, opened its doors to international travelers Monday after more than 18 months of restrictions.