The long-term effects of a kampo medicine, juzentaihoto, on maintenance of antibody titer in elderly people after influenza vaccination.

We have performed a broad-ranging analysis of the adjuvant effect of a Kampo medicine, juzentaihoto (JTT), on influenza vaccination in a multicenter randomized controlled trial. In this study, the enhancing effect of JTT on antibody titer after influenza vaccination was studied for 28 weeks in elderly people who were in the high-risk group for influenza infection. In total, 91 subjects over 65 years old were recruited from four long-term-care facilities located in Chiba, Gunma, and Toyama prefectures in Japan. Participants were randomly assigned to the JTT and the control groups. Blood samples were taken at 4 weeks before vaccination, at the time of vaccination, and then at 4, 8, 12, and 24 weeks after vaccination. The hemagglutination inhibition (HI) titers against A/California/7/2009 (H1N1), A/Victoria/210/2009 (H3N2), and B/Brisbane/60/2008 were then manually measured. A significant increase in HI titer against H3N2 was observed at week 8 after vaccination in the JTT group compared with the control group (P = 0.0229), and the HI titer of the JTT group significantly increased from 4 to 24 weeks (P = 0.0468), compared with the control group. In conclusion, our results indicated that JTT increased and prolonged antibody production against A/Victoria/210/2009 (H3N2), in particular, after influenza vaccination.