title: Effectiveness of an influenza A (H1N1) 2009 monovalent vaccine among Japanese pregnant women: a prospective observational study assessing antibody efficacy.
abstract: In order to estimate the effectiveness of an influenza A (H1N1) 2009 monovalent vaccine among pregnant women, we prospectively observed 135 Japanese pregnant women who received an influenza A (H1N1) 2009 monovalent vaccine during November 2009. We calculated an index of "antibody efficacy", in which the medical visits for respiratory illnesses were compared between those with and without post-vaccination hemagglutination inhibition (HI) titer ≥1:40. The product of antibody efficacy and achievement rate is theoretically equivalent to the vaccine effectiveness. Among all subjects, an inverse but non-significant relationship during the epidemic period was observed between post-vaccination HI titer ≥1:40 and medical visits for respiratory illnesses. After stratification by trimester at recruitment, a significant inverse association during the epidemic period was found among subjects in the first or second trimester (antibody efficacy: 91%, vaccine effectiveness: 79%). The influenza A (H1N1) 2009 monovalent vaccine administered in the first or second trimester reduced medical visits for respiratory illnesses among Japanese pregnant women.
authors.affiliation: Department of Public Health, Osaka City University Faculty of Medicine, 1-4-3, Asahi-machi, Abeno-ku, Osaka 545-8585, Japan. wakaba@med.osaka-cu.ac.jp
authors.forename: Wakaba
authors.initials: W
authors.lastname: Fukushima
authors.forename: Satoko
authors.initials: S
authors.lastname: Ohfuji
authors.forename: Masaaki
authors.initials: M
authors.lastname: Deguchi
authors.forename: Kazume
authors.initials: K
authors.lastname: Kawabata
authors.forename: Hideaki
authors.initials: H
authors.lastname: Hatayama
authors.forename: Hideki
authors.initials: H
authors.lastname: Yoshida
authors.forename: Akiko
authors.initials: A
authors.lastname: Maeda
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Hirota
mesh_terms: D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood*; D044466:Asian People; D005260:Female; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control* / Q000821:virology; D011247:Pregnancy; D037841:Pregnant People; D011446:Prospective Studies; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines