Expanding access to COVID-19 vaccines and confronting the rising dangers of climate change are set to dominate a weeklong United Nations gathering in New York that’s taking place in person after going all-virtual in 2020.

More than 100 world leaders are expected for the annual U.N. General Assembly, a sharp change from last year when the world struggled through the pandemic without vaccines. Now as nations debate how to distribute billions of doses of vaccine and the impacts of extreme weather events rise, the UNGA is back in a hybrid mode.

Heads of state scheduled to attend the event, which opens Monday and ends on Sept. 27, include U.S. President Joe Biden, U.K. Prime Minister Boris Johnson, Turkish President Recep Tayyip Erdogan and Brazilian President Jair Bolsonaro. Among the no-shows are Russia’s Vladimir Putin and China’s Xi Jinping, who regularly skip the U.N. event, as well as France’s Emmanuel Macron and Ebrahim Raisi, the new president of Iran.