Evaluation of commercially prepared vaccines for experimentally induced type A/New Jersey/8/76 influenza virus infections in mice and squirrel monkeys.

Mice and squirrel monkeys were vaccinated and subsequently challenged at selected times to evaluate the immunoprophylactic value of vaccines against influenza virus type A/New Jersey/76. Mice were challenged with virulent, homologous virus either 17 or 60 days after vaccination with 80 chick cell-agglutinating (CCA) units of whole-virus vaccine. Vaccinated mice showed minimal lesions and virus in lung tissue and had lower lung weights than unvaccinated controls. These mice had titers of hemagglutination-inhibiting (HAI) antibody in serum of greater than 1:400, but only traces of antibody were found in lung washes. Vaccinated squirrel monkeys had significantly less illness than unvaccinated controls when challenged with virulent virus 30 days after intramuscular immunization with 200 CCA units of whole virus or 400 CCA units of split virus given either once or twice (at 30-day intervals). Equal protection was observed in all monkeys despite the absence of serum HAI antibody in some monkeys after vaccination. Anamnestic reactions were observed only in monkeys vaccinated with whole virus. The possible roles of various immune factors and antibody to neuraminidase are discussed.