title: The effect of giving influenza vaccination to general practitioners: a controlled trial [NCT00221676].
abstract: BACKGROUND
  No efficacy studies of influenza vaccination given to GPs have yet been published. Therefore, our purpose was to assess the effect of an inactivated influenza vaccine given to GPs on the rate of clinical respiratory tract infections (RTIs) and proven influenza cases (influenza positive nose and throat swabs and a 4-fold titre rise), while adjusting for important covariates.
  
  
  METHODS
  In a controlled trial during two consecutive winter periods (2002-2003 and 2003-2004) we compared (77 and 100) vaccinated with (45 and 40) unvaccinated GPs working in Flanders, Belgium. Influenza antibodies were measured immediately prior to and 3-5 weeks after vaccination, as well as after the influenza epidemic. During the influenza epidemic, GPs had to record their contact with influenza cases and their own RTI symptoms every day. If they became ill, the GPs had to take nose and throat swabs during the first 4 days. We performed a multivariate regression analysis for covariates using Generalized Estimating Equations.
  
  
  RESULTS
  One half of the GPs (vaccinated or not) developed an RTI during the 2 influenza epidemics. During the two influenza periods, 8.6% of the vaccinated and 14.7% of the unvaccinated GPs had positive swabs for influenza (RR: 0.59; 95%CI: 0.28 - 1.24). Multivariate analysis revealed that influenza vaccination prevented RTIs and swab-positive influenza only among young GPs (ORadj: 0.35; 95%CI: 0.13 - 0.96 and 0.1; 0.01 - 0.75 respectively for 30-year-old GPs). Independent of vaccination, a low basic antibody titre against influenza (ORadj 0.57; 95%CI: 0.37 - 0.89) and the presence of influenza cases in the family (ORadj 9.24; 95%CI: 2.91 - 29) were highly predictive of an episode of swab-positive influenza.
  
  
  CONCLUSIONS
  Influenza vaccination was shown to protect against proven influenza among young GPs. GPs, vaccinated or not, who are very vulnerable to influenza are those who have a low basic immunity against influenza and, in particular, those who have family members who develop influenza.
authors.affiliation: Department of Family Medicine, Centre for General Practice, University of Antwerp, University of Antwerp - Campus Drie Eiken, Universiteitsplein 1, 2610 Antwerp, Belgium. barbara.michiels@pandora.be
authors.forename: Barbara
authors.initials: B
authors.lastname: Michiels
authors.forename: Hilde
authors.initials: H
authors.lastname: Philips
authors.forename: Samuel
authors.initials: S
authors.lastname: Coenen
authors.forename: Fernande
authors.initials: F
authors.lastname: Yane
authors.forename: Toon
authors.initials: T
authors.lastname: Steinhauser
authors.forename: Sofie
authors.initials: S
authors.lastname: Stuyck
authors.forename: Joke
authors.initials: J
authors.lastname: Denekens
authors.forename: Paul
authors.initials: P
authors.lastname: Van Royen
mesh_terms: D001530:Belgium; D003428:Cross Infection / Q000517:prevention & control; D006801:Humans; D009980:Influenza A virus / Q000302:isolation & purification; D009981:Influenza B virus / Q000302:isolation & purification; D007252:Influenza Vaccines / Q000009:adverse effects; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control*; D015999:Multivariate Analysis; D010821:Physicians, Family; D012044:Regression Analysis; D012141:Respiratory Tract Infections / Q000453:epidemiology*
chemical_list: D007252:Influenza Vaccines