Steens, A.

vaccination influenza vaccine control study condition pandemic effectiveness symptom onset 7 days estimate disease hospitalisation symptom onset population vaccination date influenza vaccination patient netherland individual index date infection ≥ 60 years pandemic influenza vaccination database 14 days ve estimates 2009 influenza health vaccine effectiveness analysis influenza vaccines ph 1n infection adjuvanted pandemic influenza vaccine vaccinated cases ph 1n hospitalisation steen breakthrough infections vaccination coverage number ipci database case-control study coverage 2009 pandemic influenza table h 1n vaccine exposure pandemic influenza information result figure ve estimate unexposed trial index hospitalised design group vaccinated immunogenicity surveillance history november dutch influenza vaccine effectiveness response di pietrantonj c adjuvanted influenza vaccines author van der lj 6 months impact influenza vaccination programmes vaccinee network laboratory breakthrough case-control