The FDA's Vaccines and Related Biological Products Advisory Committee endorsed a slightly different influenza vaccine composition for the 2013-2014 flu season, compared with that of the previous season. The committee recommended substituting two vaccine strains while retaining the A/California/7/2009pdm09-like virus. The committee also released recommendations for quadrivalent vaccines, noting that "global influenza virus surveillance data related to epidemiology and antigenic characteristics, serological responses to 2012-2013 seasonal vaccines, and the availability of candidate strains and reagents" were used as the basis for the recommendations.