The development of a highly effective homologous immunity to a strain of P. vivax following recovery from a naturally induced infection is now widely recognized. In further study of the subject it appeared desirable to ascertain the efficiency of the process by determining the ability of such an immune to withstand massive doses of the homologous strain of parasites.
A series of experiments along the following general lines was performed. As test case there was selected a patient who had recently recovered from a naturally induced attack of tertian malaria produced by the McCoy strain of P. vivax, and who still harbored parasites in the peripheral circulation. As a control there was selected a susceptible patient with a negative history for whom malaria therapy had been prescribed. The parasites for inoculation of the test case and control were to be derived from the blood of a patient experiencing an acute attack of tertian malaria produced by the McCoy vivax strain, with a moderate to high density of parasites in the peripheral circulation.