Measuring influenza vaccine efficacy: what is the comparator?
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Study shows different influenza vaccine effectiveness (IVE) estimates with different control groups.
Why this matters
Pan-negative controls may be less valid for estimating IVE because many of these patients may have noninfectious causes of influenza-like illness (ILI) or acute respiratory infection (ARI).
Test-negative design, case-control study.
Dutch Sentinel Practices of NIVEL Primary Care Database.
Patients with known influenza vaccination status swabbed for ILI or ARI.
IVE estimated from 2003/2004 to 2013/2014.
Adjusted for age, diagnosis, chronic disease, and respiratory allergy.
3 sets of controls: testing negative for influenza only (group 1); but positive for respiratory syncytial viruses, rhinovirus, or enterovirus (group 2); and “pan-negative’ for all viruses tested (group 3).