Experimentally induced immunity to chlamydial abortion of cattle

Vaccination against bovine abortion caused by chlamydiae which, in earlier trials, failed to protect cattle against challenge by chlamydiae administered either by subcutaneous or intramuscular injection, protected against intradermal challenge. The implications of this. latter finding are discussed in the light of the apparent epidemiologic pattern of the disease, particularly in regard to the possible nature of the immune response and the natural mode of transmission of the agent.