HELSINKI—Thousands of people gathered in European capitals Saturday to protest vaccine passports and other requirements governments have imposed in hopes of ending the COVID-19 pandemic. Demonstrations took place in Helsinki, London, Paris, and Stockholm. In Sweden, where vaccine certificates are required to attend indoor events with more than 50 people, some 3,000 demonstrators marched through central Stockholm and assembled in a main square for a protest organized by the Frihetsrorelsen—or Freedom Movement. A similar demonstration with some 1,000 participants was held also in Goteborg, Sweden’s second-largest city. The Finnish government authorized local and regional authorities just before Christmas to introduce “extensive and full measures” in response to rising virus cases involving the omicron variant. The restrictions included limiting or prohibiting events, moving university classes online, limiting restaurant service, and closing venues where people have a higher risk of exposure. Restaurants and events are allowed to require vaccine passports. Police said …