Yellow fever now states that a single dose of vaccination is sufficient to confer lifelong immunity against yellow fever disease." The attenuated live vaccine stem 17D was developed in 1937 by Max Theiler. The World Health Organization (WHO) recommends routine vaccinations for people living in affected areas between the 9th and 12th month after birth. Up to one in four people experience fever, aches, and local soreness and redness at the site of injection. In rare cases (less than one in 200,000 to 300,000), the vaccination can cause yellow fever vaccine-associated viscerotropic disease, which is fatal in 60% of cases. It is
Arnold Theiler sickness with a combination of live virus and equine antiserum. This disease is now known to be caused by a pegivirus. Theiler was the first Director of the Onderstepoort Veterinary Research Institute, outside Pretoria. This institute under his leadership carried out research on African horse sickness, sleeping sickness, malaria, East Coast fever ("Theileria parva") and tick-borne diseases such as redwater, heartwater and biliary. The University of Pretoria Faculty of Veterinary Science was established there in 1920 which enabled veterinarians to train locally for the first time. Theiler became the first dean of this faculty. He married Emma Sophie Jegge (1861–1951)