title: Detection of influenza vaccine effectiveness among nursery school children: Lesson from a season with cocirculating respiratory syncytial virus.
abstract: In the winter influenza epidemic season, patients with respiratory illnesses including respiratory syncytial virus (RSV) infections increase among young children. Therefore, we evaluated the effectiveness of influenza vaccine against influenza-like illness (ILI) using a technique to identify outbreaks of RSV infection and to distinguish those patients from ILI patients. The study subjects were 101 children aged 12 to 84 months attending nursery school. We classified the cases into 6 levels based on the definitions of ILI for outcomes. We established observation periods according to information obtained from regional surveillance and rapid diagnostic tests among children. Multivariate odds ratios (ORs) for each case classification were obtained using a logistic regression model for each observation period. For the entire observation period, ORs for cases with fever plus respiratory symptoms were reduced marginally significantly. For the local influenza epidemic period, only the OR for the most serious cases was significantly decreased (0.20 [95%CI: 0.04-0.94]). During the influenza outbreak among the nursery school children, multivariate ORs for fever plus respiratory symptoms decreased significantly (≥ 38.0°C plus ≥ one symptoms: 0.23 [0.06-0.91), ≥ 38.0°C plus ≥ 2 symptoms: 0.21 [0.05-0.85], ≥ 39.0°C plus ≥ one symptoms: 0.18 [0.04-0.93] and ≥ 39.0°C plus ≥ 2 symptoms: 0.16 [0.03-0.87]). These results suggest that confining observation to the peak influenza epidemic period and adoption of a strict case classification system can minimize outcome misclassification when evaluating the effectiveness of influenza vaccine against ILI, even if influenza and RSV cocirculate in the same season.
authors.affiliation: a Department of Public Health ; Osaka City University Graduate School of Medicine ; Osaka , Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Nakata
authors.forename: Megumi
authors.initials: M
authors.lastname: Fujieda
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Miki
authors.forename: Wakaba
authors.initials: W
authors.lastname: Fukushima
authors.forename: Satoko
authors.initials: S
authors.lastname: Ohfuji
authors.forename: Akiko
authors.initials: A
authors.lastname: Maeda
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Kase
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Hirota
mesh_terms: D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D007251:Influenza, Human / Q000175:diagnosis / Q000473:pathology* / Q000517:prevention & control*; D008297:Male; D018357:Respiratory Syncytial Virus Infections / Q000175:diagnosis* / Q000473:pathology*; D012578:Schools, Nursery; D016896:Treatment Outcome
chemical_list: D007252:Influenza Vaccines
keywords: RSV infection; case classification; influenza vaccine effectiveness; influenza-like illness (ILI); observation period; outcome misclassification