Antibody response to influenza vaccine in adults vaccinated with identical vaccine strains in consecutive years

Fifty seven hospital workers received influenza vaccine in November 2003, and the serum HI antibody titer was determined before, 2 and 4 weeks after the vaccination. Thirty seven were vaccinated in November, 2002 consecutively (the repeated vaccination group), and the remaining 20 had not been vaccinated in the previous year (the single vaccination group). Six of the repeated vaccination group received both influenza and hepatitis B vaccination in September, 2004 and the antibody responses were examined 2 weeks later. Two and four weeks after the 2003‐vaccination, the HI antibody titers to A/H1N1, A/H3N2, and B in the repeated vaccination group were significantly lower than in the single vaccination group (P