Rocky Mountain spotted fever vaccine: a regional need.

Because the killed Rickettsia vaccines have failed to provide protection against Rocky Mountain spotted fever, we approached the problem of protective immunity to Rickettsia rickettsii with a closely related, live, less pathogenic spotted fever Rickettsia. Guinea pigs vaccinated with R conorii produced antibodies to spotted fever group rickettsiae and did not have fever or other signs of illness after challenge with R rickettsii. A vaccine against Rocky Mountain spotted fever would be useful in some medical practices in the southeastern United States because of the life-threatening nature of the disease, including the possibility of a fulminant course and the frequent difficulty in diagnosis. Further studies should be pursued toward the goal of developing an effective vaccine against Rocky Mountain spotted fever.