Factors affecting the acquisition of resistance against Schistosoma mansoni in the mouse. 2. The time at which resistance to reinfection develops.

Mice developed a partial resistance against homologous challenge with Schistosoma mansoni as early as two weeks after primary infections of 35 to 75 cercariae, and the degree of protection increased to an apparent maximum by 6 weeks. Animals given a primary infection of only 25 cercariae required a longer period to acquire maximum resistance.