Effects of previous episodes of influenza and vaccination in preventing laboratory-confirmed influenza in Navarre, Spain, 2013/14 season Castilla, Jesús and Navascués, Ana and Fernández-Alonso, Mirian and Reina, Gabriel and Albéniz, Esther and Pozo, Francisco and Álvarez, Nerea and Martínez-Baz, Iván and Guevara, Marcela and García-Cenoz, Manuel and Irisarri, Fátima and Casado, Itziar and Ezpeleta, Carmen and Primary Health Care Sentinel Network and Network for Influenza Surveillance in Hospitals of Navarra, Eurosurveillance, 21, 30243 (2016), https://doi.org/10.2807/1560-7917.ES.2016.21.22.30243