BRUSSELS—EU leaders agreed Tuesday to donate at least 100 million doses of COVID-19 vaccines to poorer nations by the end of the year as supplies steadily rise across Europe. Gathered in Brussels for a two-day summit, the 27 leaders backed a text in which they pledge to continue efforts “to increase global vaccine production capacities in order to meet global needs.” Leaders also called “for work to be stepped up to ensure global equitable access to COVID-19 vaccines” and reiterated their support for the UN-backed COVAX program. COVAX aims to ensure equitable access to COVID-19 shots for low-and middle-income countries. The program suffered a major setback last week when its biggest supplier, the Serum Institute of India, announced it would likely not export any more vaccines until the end of the year due to the COVID-19 crisis on the subcontinent. Leaders acknowledged that vaccination has finally picked up across their …