Microsoft tycoon Bill Gates holds a vial

Microsoft tycoon Bill Gates holds a vial of vaccine during a press conference at the GAVI (Global Alliance for Vaccines and Immunisation) conference, in London, on June 13, 2011. Britain and Bill Gates joined forces Monday to pledge more than half the 3.7 billion dollars (2.6 billion euros) sought to vaccinate millions of children by 2015. Prime Minister David Cameron told a donors' conference in London that Britain would contribute a further 814 million pounds (1.3 billion dollars, 920 million euros) to GAVI (Global Alliance for Vaccines and Immunisation), an aid group backed by the Microsoft tycoon. AFP PHOTO / BEN STANSALL (Photo credit should read BEN STANSALL/AFP via Getty Images)