The World Health Organization’s Europe director warned that the highly transmissible COVID-19 variant first identified in India is “poised to take hold in the region,” as many countries prepare to ease restrictions and allow more social gatherings and travel across borders.

During a press briefing on Thursday, WHO’s Dr. Hans Kluge said the variant also known as the delta variant, has shown signs of being able to evade some vaccines and warned that many vulnerable populations, particularly those over age 60, remain unprotected.

“We have been here before,” warned Kluge, WHO’s European regional director. “Over the course of last summer, cases gradually rose in younger age groups and then moved into older age groups, contributing to a devastating resurgence,” he said. Kluge said that spike in COVID-19 ultimately led to more lockdowns and deaths in the fall and winter of 2020. “Let’s not make that mistake again.”

Kluge didn’t say people shouldn’t travel, but urged any travelers to do so wisely. He also called for vaccination and other public health measures to be stepped up across the continent, saying even immunization coverage “is far from sufficient to protect the region.”