Multicomponent vaccine VP-4, prepared from Streptococcus, Klebsiella, Proteus and Escherichia coli antigens, was tested for protective activity by oral administration to mice with experimental Klebsiella, Proteus and S. pneumoniae infections. Vaccine VP-4, when introduced orally (in 2-3 administrations of 2 mg), was found to produce a protective effect with respect to K. pneumoniae (the effectiveness index was equal to 5.7 and 4.3). With respect to P. vulgaris, the effectiveness index was 2.7 (immunization was made in two oral administrations of 2 mg); in pneumococcal infection preliminary oral immunization with vaccine VP-4 in two administrations in a dose of 2-4 mg produced high protective effect. Thus, immunization with vaccine VP-4, introduced orally in comparatively small doses, proved to be effective in animal models used in the experiment.