WASHINGTON (AP) – The U.S. will buy 500 million more doses of the Pfizer COVID-19 vaccine to share through the COVAX alliance for donation to 92 lower income countries and the African Union over the next year. President Joe Biden was set to make the announcement Thursday in a speech before the start of Group of Seven summit. The news was confirmed to The Associated Press by a person familiar with the matter, who spoke on condition of anonymity ahead of the president’s announcement. The person says 200 million doses would be shared this year, with the balance to be donated in the first half of 2022.