VIENNA/BRUSSELS—The European Union will ship over half a million COVID-19 shots to the Western Balkans by August using for the first time in the region a vaccine-sharing mechanism meant to help its poorer neighbors and to challenge Chinese and Russian influence. The EU move comes after China and Russia distributed millions of doses of their vaccines in the region, whose countries are candidates to join the EU, and months after the EU vaccine-sharing mechanism was set up. “Despite the current global shortage, the EU will deliver life-saving vaccines for the Western Balkans,” Oliver Varhelyi, the EU commissioner responsible for the region, told a news conference on Tuesday. The bloc plans to funnel 651,000 doses of Pfizer-BioNTech coronavirus vaccines from early May to Bosnia, Albania, North Macedonia, Kosovo, Montenegro, and Serbia. “With this initiative we are showing that we are not leaving the region behind,” Austrian Foreign Minister Alexander Schallenberg said. …