A Yemeni babyA Yemeni child reacts as he receives a diphtheria vaccine at a health center in Sanaa, Yemen, July 30, 2019. (Photo by Mohammed Mohammed/Xinhua) (Photo by Mohammed Mohammed/Xinhua)

A Yemeni child reacts as he receives a diphtheria vaccine at a health center in Sanaa, Yemen, July 30, 2019. (Photo by Mohammed Mohammed/Xinhua)

A Yemeni child reacts as he receives a diphtheria vaccine at a health center in Sanaa, Yemen, July 30, 2019. (Photo by Mohammed Mohammed/Xinhua)

A Yemeni child reacts as he receives a diphtheria vaccine at a health center in Sanaa, Yemen, July 30, 2019. (Photo by Mohammed Mohammed/Xinhua)

A Yemeni child reacts as he receives a diphtheria vaccine at a health center in Sanaa, Yemen, July 30, 2019. (Photo by Mohammed Mohammed/Xinhua)