Value of antirabies vaccine with and without serum against severe challenges.

Earlier studies with antirabies serum and vaccine have been extended to determine the value of serum, vaccine, or serum and vaccine combined against rabies challenges of increasing degrees of severity. While serum alone was not found to have any protective effect, vaccine alone was sufficient against mild challenges, the superiority of combined therapy with both serum and vaccine becoming evident at a challenge of about 50 LD(50). With challenges of over 300 LD(50) no treatment was of any value. It was also found that with a recommended optimum dose of serum, the usual vaccine dose could be halved-a matter of importance in countries with a high incidence of neuroparalytic accidents following administration of nervous tissue vaccine.