Sera from five of six persons convalescent from yellow fever in Rio de Janeiro, Brazil, 1928, protected M. rhesus against lethal doses of monkey blood-virus. The specimen giving negative results against blood-virus, as well as two others that gave positive results, protected monkeys against infection by known infective A. aegypti.
The serum of four native Africans who had yellow fever in as many localities in West Africa were tested against the same doses of blood-virus. Three conferred passive immunity and one failed. The serum that failed protected six monkeys in tests done before and after this experiment.
On the basis of these experiments, the conclusion of our previous report is further confirmed, that immunological evidence is added to the identity of yellow fever as it occurs in the Western Hemisphere and West Africa.