Time to earliest peak serum antibody response to influenza vaccine in the elderly.

The earliest time at which serum antibody levels peak following administration of an influenza virus vaccine in elderly persons is not clearly defined. We compared the time intervals of 1 and 2 weeks after vaccination. A commercial trivalent vaccine containing the hemagglutinins of influenza viruses A/Texas/36/91 (H1N1), A/Johannesburg/33/94 (H3N2), and B/Harbin/7/94 was used. The hemagglutination inhibition (HAI) antibody titers at 1 week after vaccination were significantly lower than the HAI titers at 2 weeks postvaccination for all three vaccine components.