A security worker and a sign to remind travellers to wear a face mask at Amsterdam Schiphol airport on December 2, 2021 in Amsterdam, Netherlands. The Netherlands and other nations worldwide temporarily banned most travellers from South Africa after a new variant of Covid-19 named Omicron was discovered. Omicron has sparked worries around the world that it could resist vaccinations and prolong the nearly two-year Covid-19 pandemic. (Photo by Pierre Crom/Getty Images)
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