A health worker gives a polio vaccine to a child in northwest Pakistan's Peshawar on Feb. 18, 2020. According to local media reports, Pakistan commenced the nationwide polio vaccination campaign on Monday, targeting some 39.6 million children under the age of five. (Photo by Saeed Ahmad/Xinhua)

A health worker gives a polio vaccine to a child in northwest Pakistan's Peshawar on Feb. 18, 2020. According to local media reports, Pakistan commenced the nationwide polio vaccination campaign on Monday, targeting some 39.6 million children under the age of five. (Photo by Saeed Ahmad/Xinhua)

A health worker gives a polio vaccine to a child in northwest Pakistan's Peshawar on Feb. 18, 2020. According to local media reports, Pakistan commenced the nationwide polio vaccination campaign on Monday, targeting some 39.6 million children under the age of five. (Photo by Saeed Ahmad/Xinhua)