Live Brucella abortus strain 19 attenuated vaccine (standard dose vaccine) is the most widely used against bovine brucellosis. Even though it induces reasonable protection against Brucella abortus, persistent serological responses interfere with brucellosis diagnosis. To minimize residual antibody titers and to prevent occasional persistent vaccinal infection, a reduced dose vaccine with a CFU per dose of 3 × 108 to 3 × 109 organisms subcutaneously to calves is advocated. However, it is anticipated that some animals may develop persistent antibody titres and may abort. Hence, a study was conducted to evaluate safety, incidence of vaccine induced abortions and isolate excretion of vaccinal organism during parturition after vaccination with Brucella abortus S19 reduced dose vaccine by subcutaneous route in pregnant cattle. One hundred and six healthy pregnant cattle at different stages of gestation were vaccinated with Brucella abortus S19 reduced dose subcutaneous vaccine. All the animals were followed upto parturition. No abortion was observed in any of the vaccinated animals. At normal parturition, the amniotic fluid samples were collected aseptically from 20 vaccinated cows, and the samples were bacteriologically analysed for the presence of the vaccine strain. All these samples were tested negative for Brucella abortus in microbiological culture examination. It can be concluded that Brucella abortus S19 reduced dose subcutaneous route vaccine can be safely used in pregnant cattle for prevention of brucellosis
