However, vaccination with homologous B/Florida/04/2006 virus NA (Fig. 4B) and heterologous B/Malaysia/2506/2004 virus NA (Fig. 4C) prior to infection with B/Florida/04/2006 resulted in lower viral titers compared to guinea pigs vaccinated with an irrelevant control protein, as measured by the area under the curve (AUC) of donor nasal wash virus titers (Fig. 4D). The gene discussed is XK; the disease is infection.