title: Association between monovalent influenza A (H1N1) pdm09 vaccine and pneumonia among the elderly in the 2009-2010 season in Japan: A case-control study.
abstract: We investigated the association between monovalent influenza A (H1N1) pdm09 (H1N1pdm) vaccine and pneumonia in elderly people. Study design was a hospital-based, matched case-control study. Cases comprised patients ≥ 65 years old who had been newly diagnosed with pneumonia. For each case, 2 controls were defined as individuals with other diseases (not pneumonia) who were matched by sex, age, entry date, and the visited hospital. Study period was the interval from 1 September 2009 until 30 September 2010. Because a pandemic of influenza A (H1N1) occurred during study period, we analyzed selected subjects who had enrolled during the influenza A (H1N1) pandemic. We calculated the odds ratios (ORs) and 95% confidence intervals (CIs) for pneumonia in H1N1pdm-vaccinated subjects compared with unvaccinated subjects using a conditional logistic regression model to assess the association between H1N1pdm vaccine and pneumonia. The subjects during the period of the influenza A (H1N1) pandemic were 20 cases and 40 controls. Subjects who had received H1N1pdm vaccine showed a significantly decreased OR for pneumonia (OR = 0.10, 95% CI = 0.01-0.98) compared with unvaccinated subjects. In conclusion, H1N1pdm vaccination may have prevented pneumonia among the elderly during the 2009-2010 influenza A (H1N1) pandemic in Japan.
authors.affiliation: a Department of Public Health; Faculty of Medicine; Osaka City University ; Osaka , Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Kondo
authors.forename: Kanzo
authors.initials: K
authors.lastname: Suzuki
authors.forename: Masakazu
authors.initials: M
authors.lastname: Washio
authors.forename: Satoko
authors.initials: S
authors.lastname: Ohfuji
authors.forename: Wakaba
authors.initials: W
authors.lastname: Fukushima
authors.forename: Akiko
authors.initials: A
authors.lastname: Maeda
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Hirota
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D007251:Influenza, Human / Q000150:complications* / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology; D007564:Japan / Q000453:epidemiology; D008297:Male; D011014:Pneumonia / Q000453:epidemiology* / Q000517:prevention & control* / Q000821:virology
chemical_list: D007252:Influenza Vaccines
keywords: ADL, activities of daily living; CI, confidence interval; COPD, chronic obstructive pulmonary disease; H1N1pdm, monovalent influenza A (H1N1) pdm09; OR, odds ratio; TIV, trivalent seasonal influenza vaccine; effectiveness; elderly people; matched case-control study; monovalent influenza A (H1N1) pdm09 vaccine; pneumonia