Successful Vaccinia Infection Without a Local Lesion

Abstract

Human subjects were studied who were apparently successfully infected with vaccinia virus, but who failed to develop a local vaccinia lesion. Of prime interest were those in whom the first infection with vaccinia virus failed to produce a lesion. A subsequent rise in antibody titer and/or the appearance of delayed hypersensitivity to inactive virus indicated that the lesion failure was not due to improper technique or inactive inoculum. Virus multiplication must have occurred. It is suggested that the local lesion is due to the development of delayed hypersensitivity to the viral antigens and that in some subjects the hypersensitivity development is either lacking entirely or delayed. In such cases lesion formation will not accompany successful infection. The observations recorded here on lesion failure are consistent with this hypothesis.