President Joe Biden is set to announce that the U.S. is doubling, to 1 billion doses, its purchase of Pfizer’s COVID-19 shots to share with the world. Biden is also set to embrace a goal of vaccinating 70% of the global population within the next year. The stepped-up U.S. commitment will be the cornerstone of a global vaccination summit the president is convening virtually Wednesday on the sidelines of the U.N. General Assembly. Biden will push well-off nations to do more to get the coronavirus under control around the world. Word of Biden’s plan comes from two senior Biden administration officials who spoke on the condition of anonymity to preview the president’s remarks.