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J Infect Dis. 2017 Aug 15;216(4):415-424. doi: 10.1093/infdis/jix268.

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

Author information

1
Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven.
2
Spaarne Gasthuis Academy, Hoofddorp.
3
Regional Laboratory for Public Health Kennemerland, Haarlem.
4
Department of Pedriatric Immunology and Infectious Diseases, Wilhelmina Children's Hospital/University Medical Center, Utrecht, The Netherlands.

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.

KEYWORDS:

influenza virus; influenza virus infection; influenza-like illness; older adults; vaccination

PMID:
28931240
DOI:
10.1093/infdis/jix268
[Indexed for MEDLINE]

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