Antigenic response to influenza virus in man. I. Neutralizing antibody response to inactivated monovalent A2 vaccine as related to prior influenza exposure.

Abstract

Brown, P., D. C. Gajdusek and J. A. Morris (NIH, Bethesda, Md. 20014). Anti-genic response to influenza virus in man. I. Neutralizing antibody response to inactivated monovalent A2 vaccine as related to prior influenza exposure. Amer. J. Epid., 1969, 90: 327–335.—Isolated Pacific island populations without earlier exposure, or with single exposures to earlier subtypes of influenza, were immunized in 1965 and 1966 with one of 4 inactivated monovalent Influenza A2 vaccines. The majority of previously unexposed subjects developed low levels of serum neutralizing antibody after a single dose of vaccine; the response was often limited to homologous antibody, and in approximately 1/5 of the subjects was slow to develop (higher titers at 7 months than at 4–7 weeks after vaccination). The response was quantitatively less intense but qualitatively similar to the primary response following natural influenza A2 infection. Subjects previously exposed only to an earlier subtype infection responded to a single dose of vaccine somewhat more frequently, rapidly, broadly, and at higher titer than the virgin group. In no subject, however, did the titer to the subtype responsible for the earlier ‘original’ infection exceed or even equal the titer to the homologous vaccine strain. Both virgin and previously exposed subjects exhibited characteristic booster type responses after a second dose of vaccine given 7 months after the first dose. Neither vaccinated nor naturally infected subjects showed any heterologous antibody to the recent A2/Hong Kong/68 variant.