A Yemeni child stands by a truck showing an advertising of launching an anti-polio vaccination campaign on December 23, 2019 in Sana'a, Yemen. A widespread vaccination campaign has launched on Monday and supported by the World Health Organization (WHO) and the United Nations Children's Fund (UNICEF), targeting more than 5.5 million children under the age of five. The campaign is a home-to-home and will continue for three days. (Photo by Mohammed Hamoud/Getty Images)
