Identification of pathogens responsible for influenza-like illness in elderly in The Netherlands

The general public is questioning the effectiveness of seasonal influenza
vaccination in elderly as a result of the general impression that all
influenza-like illness (ILI) is caused by an influenza virus infection.
However, several pathogens, both viral and bacterial, can cause ILI. A better
understanding of the percentage of ILI caused by an influenza virus infection
and the contribution of other respiratory viruses or involvement of bacteria
will allow a better appreciation of seasonal influenza vaccines. In addition,
information will be collected on the occurrence of viral and bacterial
co-infections.

Primary: to determine the percentage of ILI attributable to influenza virus in
elderly individuals >= 60 years of age
Secondary: to determine the relative contribution of influenza viral subtypes
Secondary: to determine humoral immune response to influenza virus
Secondary: to identify which microorganisms (viral and bacterial) present in
nose and nasopharynx of elderly suffering from ILI are potential other causes
for ILI
Secondary: to determine humoral immune response towards the potential pathogens
based on culture/PCR data
Secondary: to gain insight in the influence of viral presence on
co-colonization of well-known respiratory bacterial pathogens like S.
pneumoniae, H. influenza, M. catarrhalis, S. aureus in elderly by comparing
colonization during ILI and after recovery.
Secondary: to compare detection of pneumococcal detection in nasopharyngeal
swabs with saliva
Exploratory: to evaluate whether differences can be found in incidence of
influenza virus detection between subjects who have received the seasonal
influenza vaccine 2011-2012 or who did not receive the seasonal influenza
vaccine 2011-2012.
Exploratory: to evaluate whether there is a difference in the general physical
and mental health condition as assessed by SF-36 questionnaire between the
subjects that report with ILI and the whole study population

Observational cross-sectional study without an investigational medicinal
product but with invasive measurements.

The burden associated with participation are reporting of ILI, and collection
of a nasal swab and a transoral nasopharyngeal swab, and 1 tube of blood (10
ml) in case of ILI symptoms. This will be repeated 8 weeks later. The potential
risks are considered minimal. There are no benefits for the individual subjects
who participate in this trial. The results are possibly of benefit on a
population level in the future. The study population is the target of the
yearly influenza vaccination campaign.