The WHO’s Europe Director Dr. Hans Kluge weighed in on the thorny debate on Tuesday, cautioning that compulsory vaccinations should be a last resort.

“Mandates around vaccination are an absolute last resort, and only applicable when all other feasible options to improve vaccination uptake have been exhausted,” Kluge said. They should not be done “if one has not reached out first to the communities” involved, he said at a press briefing.

Mandates “have proven effective in some environments to increase vaccine uptake,” Kluge said, but added, “the effectiveness of vaccine mandates is very context-specific. The effect mandating vaccines could have on public confidence and public trust, as well as vaccination uptake, must be considered.”