Immunization with One Dose of Inactivated Influenza Vaccine

In the winter of 1996, a total of 71 working adults from 20 to 60 (m = 37.3) years of age were immunized with one or two doses of inactivated influenza vaccine formulated in Japan. The reciprocal geometric mean hemagglutination inhibition antibody titers [mean HI] and the percentage with a hemagglutination inhibition titer of > or = x 128 [percent > or = x 128], against A/ Yamagata/32/89 (H1N1), A/Uhan/359/95 (H3N2), and B/Mie/1/93 were significantly elevated by either doses. The pre-/post-vaccination mean HI of H1N1 were 61.5/668.4 with one dose, and 85.7/637.3 with two doses. The percent > x 128 were 36.5/96.2 with one dose, and 47.4/94.7 with two doses. No significant differences were apparent between one and two doses. Similarly, nonsignificant differences were observed for the other two antigens contained in the vaccine. We observed the sufficient immune response to only one dose of inactivated influenza vaccine, which emphasizes the merit of one dose method of influenza immunization.