The astonishing spread of the omicron variant could help set the stage for the pandemic to transition from overwhelming to manageable in Europe this year, a top health official said Monday, potentially offering the world a glimpse at how countries can ease restrictions while keeping the virus at bay.

That hint of hope came with a heavy dose of caution: Immunity from the surge of infections will probably wane, and new variants are likely to emerge, leaving the world vulnerable to surges that could strain health systems. In the United States, where vaccination rates are lower and death rates are considerably higher than in Western Europe, there are bigger hurdles on the path to taming the pandemic.

Dr. Hans Kluge, director for the World Health Organization’s European region, warned in a statement released Monday that it was too early for nations to drop their guard, with so many people unvaccinated around the world. But, he said, between vaccination and natural immunity through infection, "omicron offers plausible hope for stabilization and normalization.”