The World Health Organization, a U.N. agency founded in 1948, is headquartered in Geneva, Switzerland. Trump had pledged to withdraw U.S. participation by July 2021. Biden says he will rejoin on the first day of his administration.

A photo taken in the late hours of August 17, 2020 shows a sign of the World Health Organization (WHO) at their headquarters in Geneva amid the COVID-19 outbreak, caused by the novel coronavirus. (Photo by Fabrice COFFRINI / AFP) (Photo by FABRICE COFFRINI/AFP via Getty Images)