DURATION OF IMMUNITY TO REINFECTION IN GUINEA-PIGS TREATED WITH ANTIRABIES SERUM AND VACCINE, AND THE VALUE OF BOOSTER DOSES OF VACCINE IN RE-TREATMENT.

Studies undertaken to determine the resistance of guinea-pigs which have survived a moderate challenge as a result of treatment with serum and vaccine to subsequent severe challenges with homologous and heterologous strains of rabies street virus have shown that, even with large groups of animals, treatment with serum and vaccine saved nearly 70% of the animals against challenges of about 100 LD(50). The animals which survived such treatment and challenge continued to have a considerable degree of immunity to rechallenge even 15 months after the first treatment. There was no advantage in giving two booster doses of vaccine during this period. The immune status of rechallenged guinea-pigs seemed to depend primarily on the original treatment rather than on the strain of virus used for the first challenge. Guinea-pigs which survived an earlier challenge as a result of treatment fared better against the later challenge than fresh groups of treated but not challenged animals given the same challenge.