To test whether rapamycin pretreatment affects the response to vaccination, we challenged the vaccinated mice with the same strain of influenza virus at a dose that is lethal to unimmunized young mice. As shown in Fig. 6F, 9 out of 12 (75%) vehicle-treated old mice succumbed to infection even after immunization, whereas all mice that had been pretreated with rapamycin were protected by the vaccination.