title: [Burden of influenza virus type B and mismatch with the flu vaccine in Spain].
abstract: BACKGROUND
  Since the 80s two lineages of type B viruses are co - circulating in the world. Antigenic differences between them are important and it leads to lack of cross-reactivity. The impact on the burden of disease due to influenza B virus, poor foresight in estimating which of the two lineages of B viruses circulate in the season, and the consequent lack of immunity in case of including the wrong strain make that the availability of the quadrivalent vaccine is very useful. The aim of this paper is to analyze the past influenza seasons in Spain to assess the burden of disease, divergence between the vaccine strain and the circulating B and viral characteristics associated with type B in each seasonal epidemic.
  
  
  METHODS
  Review of all reports issued by the Influenza Surveillance System in Spain since the 2003-2004 season to 2012-2013.
  
  
  RESULTS
  Over the past influenza seasons, although type A was present mostly, circulation of influenza B virus in each season was observed, even being co - dominant in some of them. In a high number of seasons the divergence between the vaccine strain and the circulating strain lineage has been observed
  
  
  CONCLUSIONS
  The protective effect of influenza vaccine has varied depending on the type / subtype of influenza virus studied. The vaccine effectiveness against influenza infection by influenza B virus has varied greatly depending on the season analyzed.
authors.affiliation: Alberto Pérez Rubio. Dirección Médica. Hospital Clínico Universitario de Valladolid. Calle Ramón y Cajal 3, 47001. Valladolid, Spain. albertoprz@gmail.com.
authors.forename: Jose Ma
authors.initials: JM
authors.lastname: Eiros-Bouza
authors.forename: Alberto
authors.initials: A
authors.lastname: Pérez-Rubio
mesh_terms: D000918:Antibody Specificity; D017281:Cost of Illness; D003429:Cross Reactions; D006801:Humans; D009981:Influenza B virus; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology / Q000276:immunology* / Q000517:prevention & control; D062486:Public Health Surveillance; D012621:Seasons; D013030:Spain / Q000453:epidemiology; D016896:Treatment Outcome
chemical_list: D007252:Influenza Vaccines