In this study, a combined vaccine of rota virus, corona virus and enterotoxigenic K99 E.. toll ( ETEC) was evaluated against safety, ster­ility and potency in pregnant mice, as well as, in their infants. The anti­body level was measured in dams and their infants, using serum neutrali­zation test for rota, corona viruses, microagglutination test and mouse protection test for K99 E..coli .A challenge test was conducted in vacci­nated mice, as well as, in their infants using virulent strain of rota, coro­na viruses and K99 E.. coli strain and in control group. Trials for reisola­tion of these challengin strain were done and confirmed by using indirect fluorescent antibogdy technique ( IFA) for rota and corona viruses and specific media and biochemical test for K99 E..coli strain. The vaccine was safe and potent for dams mice and their infants as the level of anti­body titres, by using microagglutination test, was 430 geometric mean "GM" for dams mice and 355 GM for in fant mice, where the protective level was 80 GM. The mouse protection test in dams mice reached 100% and in infant mice was 80% . The serum neutralization titre (SNT) was 2.1 log ₁₀ SN titre for dams and 1.2 log_i0 titre for infants for rota virus and 2.1log_i0 SN titre dams, 1.5 log ₁₀ SN titre for corona virus, where the protective level was 0.6 log₁₀ SN titre for rota and corona visuses. The vaccine protected infant mice against challenge with virulent strains and study emphathized the transmission of passive immunity from vacci­nated dams mice to their infant mice it was clear that, mice play an im­portant role in transmission of infection through their faeces to con­taminate animal rations, as well as, human food .