Influenza-like Illness Incidence Is Not Reduced by Influenza Vaccination in a Cohort of Older Adults, Despite Effectively Reducing Laboratory-Confirmed Influenza Virus Infections. (13th July 2017)

• Record Type: Journal Article
• Authors: van Beek, Josine; Veenhoven, Reinier H; Bruin, Jacob P; van Boxtel, Renée A J; de Lange, Marit M A; Meijer, Adam; Sanders, Elisabeth A M; Rots, Nynke Y; Luytjes, Willem
• Is Part Of: Journal of infectious diseases. Volume 216:Number 4(2017:Aug. 15)
• Page Start: 415
• Page End: 424
• Publication Date: 2017-07-13
• Subjects: influenza virus -- influenza virus infection -- influenza-like illness -- older adults -- vaccination; Communicable diseases -- Periodicals; Diseases -- Causes and theories of causation -- Periodicals; Medicine -- Periodicals; Communicable Diseases -- Periodicals; Electronic journals; 616.9
• DOI: 10.1093/infdis/jix268
• Languages: English
• ISSNs: 0022-1899

Abstract

Summary: Influenza virus is responsible for 18.2%–33.3% of community-dwelling older adult influenza-like illness (ILI) cases in 2 consecutive seasons. Although vaccination protects against influenza virus infection, it had no effect on the overall number of ILI cases in older adults. Abstract: Background: Data on the relative contribution of influenza virus and other respiratory pathogens to respiratory infections in community-dwelling older adults (≥60 years) are needed. Methods: A prospective observational cohort study was performed in the Netherlands during 2 winters. Nasopharyngeal and oropharyngeal swabs were collected during influenza-like illness (ILI) episodes and from controls. Viruses and bacteria were identified by multiplex ligation–dependent probe amplification assay and conventional bacterial culture. Results: The ILI incidence in the consecutive seasons was 7.2% and 11.6%, and influenza virus caused 18.9% and 34.2% of ILI episodes. Potential pathogen were detected in 80% of the ILI events with influenza virus, coronaviruses, rhinoviruses, human metapneumovirus, respiratory syncytial virus, parainfluenza viruses, and Haemophilus influenzae being the most common. Influenza vaccination reduced influenza virus infection by 73% (95% confidence interval [CI], 26%–90%) and 51% (95% CI, 7%–74%) in ILI patients. However, ILI incidence was similar between vaccinated (7.6% and 10.8%) and nonvaccinated (4.2% and 11.4%) participants in 2011–2012 and 2012–2013, respectively ( P > .05). Conclusions: Influenza virus is a frequent pathogen in older adults with ILI. Vaccination reduces the number of influenza virus infections but not the overall number of ILI episodes: other pathogens fill the gap. We suggest the existence of a pool of individuals with high susceptibility to respiratory infections. Clinical Trials Registration: NTR3386.