As CD28 is crucial for complete T cell activation, CD28 loss is associated with increased susceptibility to infections and a weakened immune response to vaccination in older people (Saurwein-Teissl et al., 2002; Almanzar et al., 2005; Sansoni et al., 2008; Moro-García et al., 2013). The gene discussed is CD28; the disease is infection.