Fig. 1.

Primary and secondary antibody responses of 31 young adult and eight old rhesus monkeys to vaccination. The antibody responses of old monkeys were significantly reduced, but a booster immunization raised their secondary titers into the primary range for young adults. A relative scale is portrayed using area under the curve (AUC) based on computations of antibody titer from three serial dilutions of sera. Vertical arrows indicate when the two trivalent vaccines were administered