P. Loubet, N. Samih-lenzi, F. Galtier, P. Vanhems, P. Loulergue et al., Factors associated with poor outcomes among adults hospitalized for influenza in France: A three-year prospective multicenter study, Journal of Clinical Virology, vol.79, pp.68-73, 2016.
DOI : 10.1016/j.jcv.2016.04.005

M. Darvishian, M. Bijlsma, E. Hak, and E. Van-den-heuvel, Effectiveness of seasonal influenza vaccine in community-dwelling elderly people: a meta-analysis of test-negative design case-control studies, The Lancet Infectious Diseases, vol.14, issue.12, pp.1228-1267, 2014.
DOI : 10.1016/S1473-3099(14)70960-0

M. Osterholm, N. Kelley, A. Sommer, and E. Belongia, Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis, The Lancet Infectious Diseases, vol.12, issue.1, pp.36-44, 2012.
DOI : 10.1016/S1473-3099(11)70295-X

E. Belongia, M. Simpson, J. King, M. Sundaram, N. Kelley et al., Variable influenza vaccine effectiveness by subtype: a systematic review and meta-analysis of test-negative design studies, The Lancet Infectious Diseases, vol.16, issue.8, pp.942-51, 2016.
DOI : 10.1016/S1473-3099(16)00129-8

J. Vanwormer, M. Sundaram, J. Meece, and E. Belongia, A cross-sectional analysis of symptom severity in adults with influenza and other acute respiratory illness in the outpatient setting, BMC Infectious Diseases, vol.2011, issue.3, p.231, 2014.
DOI : 10.1503/cmaj.1041470

J. Castilla, P. Godoy, A. Dominguez, I. Martinez-baz, J. Astray et al., Influenza Vaccine Effectiveness in Preventing Outpatient, Inpatient, and Severe Cases of Laboratory-Confirmed Influenza, Clinical Infectious Diseases, vol.4, issue.2, pp.167-75, 2013.
DOI : 10.1371/journal.pone.0008540

C. Arriola, E. Anderson, J. Baumbach, N. Bennett, S. Bohm et al., Does Influenza Vaccination Modify Influenza Severity? Data on Older Adults Hospitalized With Influenza During the 2012???2013 Season in the United States, Journal of Infectious Diseases, vol.212, issue.8, pp.1200-1208, 2015.
DOI : 10.1378/chest.10-2792

C. Hannoun, W. Dab, and J. Cohen, A new influenza surveillance system in France: The Ile-De-France ?GROG?. I. Principles and methodology, European Journal of Epidemiology, vol.73, issue.9, pp.285-93, 1989.
DOI : 10.1001/archpedi.1976.02120070041009

S. Française-de-médecine-générale, At what time of the year do the general practitioners vaccinate most against influenza elderly aged 64 years or older, 2016.

B. Biere, B. Bauer, and B. Schweiger, Differentiation of Influenza B Virus Lineages Yamagata and Victoria by Real-Time PCR, Journal of Clinical Microbiology, vol.48, issue.4, pp.1425-1432, 2010.
DOI : 10.1128/JCM.02116-09

A. Van-gageldonk-lafeber, M. Van-der-sande, M. Heijnen, M. Peeters, A. Bartelds et al., Risk factors for acute respiratory tract infections in general practitioner patients in The Netherlands: a case-control study, BMC Infectious Diseases, vol.124, issue.Suppl 8, p.35, 2007.
DOI : 10.1017/S0950268899003660

T. Liu, Z. Li, S. Zhang, S. Song, W. Julong et al., Viral Etiology of acute respiratory tract infections in hospitalized children and adults in Shandong Province, China, Virology Journal, vol.39, issue.2, p.168, 2015.
DOI : 10.1128/JCM.00636-10

C. Chiatti, P. Barbadoro, G. Lamura, L. Pennacchietti, D. Stanislao et al., Influenza vaccine uptake among community-dwelling Italian elderly: results from a large cross-sectional study, BMC Public Health, vol.52, issue.6, p.207, 2011.
DOI : 10.1093/oxfordjournals.epirev.a036063

D. Chan, N. Wong, E. Wong, A. Cheung, and S. Lee, Household characteristics and influenza vaccination uptake in the community-dwelling elderly: a cross-sectional study, Preventive Medicine Reports, vol.2, pp.803-811, 2015.
DOI : 10.1016/j.pmedr.2015.09.002

J. Petrie, C. Cheng, R. Malosh, J. Vanwormer, B. Flannery et al., Illness Severity and Work Productivity Loss Among Working Adults With Medically Attended Acute Respiratory Illnesses: US Influenza Vaccine Effectiveness Network 2012???2013, Clinical Infectious Diseases, vol.3, issue.RR-08, pp.448-55, 2016.
DOI : 10.1016/j.socscimed.2004.10.022

Y. Ren, Y. Yin, W. Li, Y. Lin, T. Liu et al., Risk factors associated with severe manifestations of 2009 pandemic influenza A (H1N1) infection in China: a case???control study, Virology Journal, vol.10, issue.1, p.149, 2013.
DOI : 10.1001/jama.292.11.1333

E. Kissling, B. Nunes, C. Robertson, M. Valenciano, A. Reuss et al., I- MOVE multicentre case-control study15: is there withinseason waning of influenza type/subtype vaccine effectiveness with increasing time since vaccination?, Euro Surveill, vol.1121, issue.16, 2010.
URL : https://hal.archives-ouvertes.fr/hal-01597277

H. Mclean, M. Thompson, M. Sundaram, B. Kieke, M. Gaglani et al., Influenza Vaccine Effectiveness in the United States During 2012-2013: Variable Protection by Age and Virus Type, Journal of Infectious Diseases, vol.96, issue.24, pp.1529-1569, 2015.
DOI : 10.1073/pnas.96.24.14001

S. Sullivan, K. Carville, M. Chilver, J. Fielding, K. Grant et al., Pooled influenza vaccine effectiveness estimates for Australia, Epidemiol Infect, vol.2016, pp.2012-20141

H. Mclean, J. Meece, and E. Belongia, Influenza vaccination and risk of hospitalization among adults with laboratory confirmed influenza illness, Vaccine, vol.32, issue.4, pp.453-460, 2014.
DOI : 10.1016/j.vaccine.2013.11.060

I. Casado, A. Domínguez, D. Toledo, J. Chamorro, L. Force et al., Effect of influenza vaccination on the prognosis of hospitalized influenza patients, Exp Rev Vacc, vol.15, issue.3, pp.425-457, 2016.

V. Gupta, F. Dawood, S. Rai, S. Broor, R. Wigh et al., Validity of clinical case definitions for influenza surveillance among hospitalized patients: results from a rural community in North India, Influenza and Other Respiratory Viruses, vol.167, issue.3, pp.321-330, 2013.
DOI : 10.1093/aje/kwm375

L. Jiang, V. Lee, W. Lim, M. Chen, Y. Chen et al., Performance of case definitions for influenza surveillance, Eurosurveillance, vol.20, issue.22, p.21145, 2015.
DOI : 10.1371/journal.pone.0012474