The objective of WP2 is to measure in the elderly population at primary care and hospital level, early and late in the season, the influenza vaccine effectiveness against laboratory confirmed (PCR positive) and the impact of various types of influenza vaccines (e.g. adjuvanted vs non adjuvanted) in order to:

1.  identify  vaccine  types  (adjuvanted  vs  not  adjuvanted,  live  vs  attenuated,  trivalent  vs  quadrivalent)  and
brands with different effectiveness,

2.  understand the factors affecting influenza vaccine effectiveness (VE), the duration of  protection, the role
of repeated seasonal vaccinations,

3.  identify key influenza virus phenotypic or genotypic evolutions that could affect vaccine performances,

4.  estimate  the  impact  of  the  influenza  vaccine  in  decreasing  defined  clinical  outcomes  (influenza
hospitalisations, deaths attributed to influenza) in the elderly population. Note that WP4 will measure the
potential  indirect  effect  of  influenza  vaccination  in  children  on  influenza  incidence  in  the  elderly  in
countries  that  have  introduced  universal  influenza  vaccination  in  children  into  their  vaccination
programme (Finland, UK)