title: Does seasonal vaccination affect the clinical presentation of influenza among the elderly? A cross-sectional analysis in the outpatient setting in France, 2003-2014.
abstract: Vaccine-induced protection against influenza is not optimal, however it has been suggested that the vaccine may reduce the severity of symptoms among those who develop illness despite being vaccinated. We tested this hypothesis within a countrywide, sentinel general practitioners-based surveillance system in France. We included 2277 individuals aged 65years or older (of whom 1293 had been vaccinated against influenza, 56.8%) who consulted a general practitioner because of an acute respiratory infection (ARI) during 2003-2014. All patients were taken a nasopharyngeal swab, and information was collected on demographic characteristics and symptoms at disease onset. All specimens were tested for respiratory viruses and, if positive for influenza, the virus type and subtype were determined. We compared the average maximum temperature and the frequency of each symptom, between non-vaccinated and vaccinated influenza patients. We then used logistic regression models to calculate the odds of presenting with each symptom between vaccinated vs. non-vaccinated patients, adjusting by age group, virus (sub)type and season. Overall, 675 ARI patients (29.6%) tested positive for influenza. The A(H3) virus caused the majority of cases (55.1%), followed by influenza B (22.9%), A not-subtyped (11.7%), and A(H1) (10.3%) viruses. Compared to non-vaccinated influenza patients, those who had been vaccinated had a slightly reduced maximum temperature and presented less frequently with myalgia, shivering and headache. In stratified analyses, the observed effect was limited to patients infected with A(H3) or type B viruses. After adjusting by age group, virus (sub)type and season, the difference remained statistically significant only for headache, which was less frequent among vaccinated individuals (odds ratio 0.69, 95% confidence intervals 0.48-0.98). In conclusion, the vaccine was found to be modestly associated with less severe clinical presentation of influenza among the elderly. Our findings reinforce the need for influenza vaccines providing better protection.
authors.affiliation: Open Rome (Organize and Promote Epidemiological Network), Paris, France; Réseau des GROG, Paris, France. Electronic address: amos@openrome.org.
authors.forename: Anne
authors.initials: A
authors.lastname: Mosnier
authors.affiliation: Open Rome (Organize and Promote Epidemiological Network), Paris, France; Réseau des GROG, Paris, France. Electronic address: idaviaud@openrome.org.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Daviaud
authors.affiliation: Open Rome (Organize and Promote Epidemiological Network), Paris, France. Electronic address: saverio.caini@gmail.com.
authors.forename: Saverio
authors.initials: S
authors.lastname: Caini
authors.affiliation: Réseau des GROG, Paris, France. Electronic address: dr.herve.berche@wanadoo.fr.
authors.forename: Hervé
authors.initials: H
authors.lastname: Berche
authors.affiliation: Laboratoire de Virologie, Centre Hospitalier Universitaire de Toulouse, Toulouse, France. Electronic address: mansuy.jm@chu-toulouse.fr.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Mansuy
authors.affiliation: Centre National de Référence des virus influenzae, Unité de Génétique moléculaire des virus à ARN, CNRS UMR3569, Université Paris Diderot Sorbonne Paris Cité, Institut Pasteur, Paris, France. Electronic address: sylvie.van-der-werf@pasteur.fr.
authors.forename: Sylvie
authors.initials: S
authors.lastname: van der Werf
authors.affiliation: Open Rome (Organize and Promote Epidemiological Network), Paris, France; Réseau des GROG, Paris, France. Electronic address: jmcoco@openrome.org.
authors.forename: Jean Marie
authors.initials: JM
authors.lastname: Cohen
authors.affiliation: Centre National de Référence des virus influenzae, CBPE, Hospices Civils de Lyon et Virpath, Université Claude Bernard Lyon, Lyon, France. Electronic address: bruno.lina@univ-lyon1.fr.
authors.forename: Bruno
authors.initials: B
authors.lastname: Lina
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D007252:Influenza Vaccines / Q000008:administration & dosage*; D007251:Influenza, Human / Q000453:epidemiology / Q000473:pathology* / Q000517:prevention & control*; D008297:Male; D009975:Orthomyxoviridae / Q000145:classification / Q000302:isolation & purification; D010045:Outpatients
chemical_list: D007252:Influenza Vaccines
keywords: Elderly; Illness severity; Influenza; Influenza vaccine