Gay and bisexual men were banned from donating blood over concern that HIV could contaminate the blood supply. Vesna Andjic/Getty Images hide caption

toggle caption Vesna Andjic/Getty Images

James Harrison was recognized in 2003 with the Guinness World Record for the most blood donated by one person. DAVID GRAY/Reuters /Landov hide caption

toggle caption DAVID GRAY/Reuters /Landov

Several countries, including Australia, Japan and Great Britain, already encourage blood donations from some gay men. Kevin Curtis/Getty Images/Science Photo Library hide caption

toggle caption Kevin Curtis/Getty Images/Science Photo Library

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