Antibody Response of Swine to Repeated Vaccination with Formalin-Inactivated, Purified Swine Influenza Virus.

Abstract

Four groups of 16 pigs each were vaccinated by subcut. injn. of 0.5 mg. of formolized swine influenza virus. A 2d injn. was given to each group at intervals of 1, 2, 3 and 4 weeks, respectively. The antibody response, measured by inhibition of the hemagglutinative reaction, was proportional to the length of the interval between vaccinations; the antibody level after 2d vaccination at the 1-week interval was no higher than after 1 injn., but that after the 4-weeks interval was a 2-fold dilution higher. The rate of decline in titer was the same in all groups. The interval of 3 weeks between vaccinations appeared to be best for induction and maintenance of highest titer.