Since yellow fever convalescent serum protects monkeys against infection from yellow fever virus, and in the absence of a better prophylactic measure, it has been customary in this laboratory to give injections of human convalescent serum to all who handle the virus. These have been given, as a rule, at one- to two-week intervals, and the amount injected has varied between 10 and 12 cc. When accidents were known to have occurred, much larger amounts were used. In order to determine experimentally, in monkeys, the approximate extent and duration of passive immunity conveyed by convalescent serum, the following experiments were carried out.
EXPERIMENT 1 Four monkeys, nos. A1, A2, A3, and A4, which had recovered from attacks of yellow fever, were bled from the heart. The serum was pooled, centrifugalized, and filtered through a Berkefeld V candle. No preservative was added. The serum was tested out in monkeys in varying amounts against a uniform dose of virus.