Immunity studies in calves vaccinated with a multivalent live respiratory vaccine composed of I.B.R., parainfluenza 3 and bovine adenovirus type 3.

The persistence of systemic and local antibodies was studied after two intranasal administrations of the vaccine, six weeks apart. Systemic antibodies to I.B.

Local and systemic response after simultaneous intranasal inoculation of temperature-sensitive mutants of parainfluenza 3, IBR and bovine adenovirus 3.

Triple seronegative calves were exposed by the nasal route to three (ts) mutants of bovine respiratory viruses (PI3, IBR, Adeno3). After a single exposure, they responded with significant levels of serum antibodies to the three viruses. Nasal antibodies were demonstrated for PI3 and adenovirus antigens.