The WHO on Tuesday urged countries to remain calm and take “rational” measures against the fast-spreading Omicron coronavirus variant, as Germany’s next chancellor voiced support for compulsory vaccinations. The emergence of Omicron, first reported to the World Health Organization in South Africa less than a week ago, has already spread rapidly across the globe with borders shutting and dozens of countries rolling out travel restrictions in defiance of WHO advice. While so much is still unknown — no deaths have been reported from Omicron and it could take weeks to know how vaccine-resistant i…