Effect ofVaccination Schedule onImmuneResponse of Macacamulatta toCellCulture-Grown RockyMountain Spotted FeverVaccine

andindirect immunofluorescence andresistance tochallenge with104plaque-forming units ofyolksacgrownR.rickettsii wereassessed. Seroconversion wasnotedinallmonkeys after thefirst doseofvaccine. A second doseadministered 8or15daysafter the primary infection, orathird given7or30daysafter thesecond, produced no long-term effect onantibody titer. Onlymonkeys given twodoses ofvaccine ata 30-day interval showedanincrease inantibody titer during theperiod before challenge. Vaccination withone,two,orthree doses ofCECvaccine prevented development ofrashandrickettsemia after challenge. Thetwo-dose schedules appeared toinduce thehighest degree ofresistance tochallenge, asindicated by unaltered hematological parameters andbodytemperature inmonkeys. The one-andthree-dose schedules weresomewhat less effective, inthatsomechallenged monkeys within eachgroupdisplayed febrile andleukocyte responses associated withRockyMountain spotted fever infection. Ourdatasuggest that administration oftwodoses ofCEC vaccine at15-or30-day intervals isthe immunization schedule ofchoice. A formalin-inactivated RockyMountain