Oral immunization of monkeys with polyvalent dysentery vaccine.

Macaca mulatta monkeys were immunized orally with polyvalent Boivin extract of Shigella flexneri 2a, 3a, 4a, 4b, 6 and Shigella sonnei. The total immumizing dose for each component was equivalent to 1.2 X 10(12) cells. After challenge with 7.5 X 10(10) cells of a virulent S. flexneri 2a strain, out of 20 immunized animals 2 developed dysentery and 4 showed mild dyspepsia; all 6 control animals became ill with dysentery. Vaccination failed to influence the incidence, duration or the intermittent character of shigella excretion. Protective antibodies appeared in high titre in the serum of immunized animals.