WHO lists a number of factors that countries should take into account when reopening borders, including local epidemiology, transmission patterns, measures for controlling outbreaks and health service capacity.
"There is no 'zero risk' when considering the potential importation or exportation of cases in the context of international travel," WHO warns. "Therefore, thorough and continuous risk assessment and management will help identify, reduce and mitigate those risks, while balancing the socio-economic consequences of travel measures (or temporary restrictions) against potential adverse public health consequences."
As the world reopens, WHO's general advice for travelers includes practicing good personal and hand hygiene, respiratory etiquette, maintaining a physical distance of at least one meter or 3.3 feet from others and wearing a face-covering when appropriate. The organization recommends that sick travelers and at-risk individuals such as the elderly and those with chronic diseases or underlying health conditions postpone international travel to areas with community transmission.
Travelers are also encouraged to self-monitor for the potential onset of symptoms on arrival for at least 14 days and report any symptoms and their travel history to local health facilities.
The agency emphasized the importance of laboratory PCR testing immediately prior to departure or on arrival but warns against the use of "immunity certificates" for international travel due to a lack of support from scientific evidence.
WHO is also advising countries to not charge travelers for any necessary health examinations; vaccination or prophylaxis on arrival; isolation or quarantine measures; certificates specifying the measures applied or applied to baggage accompanying them.