When diplomats met to form the United Nations in 1945, one of the things they discussed was setting up a global health organization. WHO’s Constitution came into force on 7 April 1948 – a date we now celebrate every year as World Health Day.

In April 1945, during the Conference to set up the United Nations (UN) held in San Francisco, representatives of Brazil and China proposed that an international health organization be established and a conference to frame its constitution convened. On 15 February 1946, the Economic and Social Council of the UN instructed the Secretary-General to convoke such a conference. A Technical Preparatory Committee met in Paris from 18 March to 5 April 1946 and drew up proposals for the Constitution which were presented to the International Health Conference in New York City between 19 June and 22 July 1946. On the basis of these proposals, the Conference drafted and adopted the Constitution of the World Health Organization, signed 22 July 1946 by representatives of 51 Members of the UN and of 10 other nations.

The Conference established also an Interim Commission to carry out certain activities of the existing health institutions until the entry into force of the Constitution of the World Health Organization. The preamble and Article 69 of the Constitution of WHO provide that WHO should be a specialized agency of the UN. Article 80 provides that the Constitution would come into force when 26 members of the United Nations had ratified it. The Constitution did not come into force until 7 April 1948, when the 26th of the 61 governments who had signed it ratified its signature. The first Health Assembly opened in Geneva on 24 June 1948 with delegations from 53 of the 55 Member States. It decided that the Interim Commission was to cease to exist at midnight on 31 August 1948, to be immediately succeeded by WHO.