"The world has experienced mass trauma because World War Two affected many, many lives," Ghebreyesus said.
He also added that pandemic induced mass trauma is "beyond proportion and even bigger than what the world experienced" after the Second World War.
"Countries have to see it as such, and prepare for that," he warned.
Meanwhile, the WHO believes that governments don't need to introduce Covid-19 vaccination passports. Melita Vujinovic, the WHO representative in Russia said so as quoted by RBC news agency.
"But of course, the countries walk their own line, everybody is trying to allow considerable mobility of population," Vujnovic said.
According to her, the WHO cooperates with all countries that show interest in this initiative; the Organization will later give recommendations about what kind of information should be in these documents.