1793 Philadelphia yellow fever epidemic Philadelphia forced evacuation of certain neighborhoods and placed refugees in supervised camps. After the epidemic, the city inspected all houses and destroyed those it deemed unhealthy. American doctors did not identify the vector of yellow fever until the late nineteenth century. In 1881 Carlos Finlay, a Cuban doctor, argued that mosquito bites caused yellow fever; he credited Rush's published account of the 1793 epidemic for giving him the idea. He said that Rush had written: "Mosquitoes (the usual attendants of a sickly autumn) were uncommonly numerous..." In the late 1880s, Finlay's theories were confirmed in Cuba by experiments of the
Yellow fever vaccine vaccine, ten years after a primary dose, is not necessary. Since yellow fever vaccination began in the 1930s, only 12 known cases of yellow fever post-vaccination have been identified, after 600 million doses have been dispensed. Evidence showed that among this small number of "vaccine failures", all cases developed the disease within five years of vaccination. This demonstrates that immunity does not decrease with time. The World Health Organization recommends the vaccine between the ages of 9 and 12 months in areas where the disease is common. Anyone over the age of 9 months who has not been previously immunized