STEVE HOLLAND and ANDREA SHALAL U.S. President Joe Biden plans to buy and donate 500 million doses of the Pfizer coronavirus vaccine to more than 90 countries, while calling on the world's democracies to do their part to help end the deadly pandemic, the White House said. The announcement of the vaccine donation - the largest ever by a single country - comes before Biden meets leaders of the other Group of Seven advanced economies in England. "The goal of today's donation is to save lives and end the pandemic and will provide the foundation for additional actions to be…