Repeated Immunization: Possible Adverse Effects: Reevaluation of Human Subjects at 25 Years

A group of intensively immunized men, who had been subjected to detailed medical evaluations in 1956 and in 1962, was reexamined in 1971 and compared with a carefully matched control group. Clinical and laboratory studies were done to detect adverse effects induced by repeated parenteral inoculation with a variety of vaccines and toxoids. No clinical sequels attributable to long-term immunization were identified. Only one laboratory abnormality described in previous studies, elevated serum hexosamine, was observed. Few other abnormalities were detected in the immunized group; mean values were depressed for serum albumin and serum iron levels and were elevated for serum copper level and erythrocyte sedimentation rate. The findings do not exclude possible development of adverse consequences to individuals exposed to a similar course of inoculations with higher dosages or with an equally intensive course of injections with a single antigen or closely related antigens.