Durability of vaccinia immunization based on reaction at the rechallenge site.

The authors reviewed the immunization records of 621 patients who received vaccinia vaccination in our Occupational Medicine Clinic between July 26, 1994 and October 11, 2001 to evaluate the durability of the vaccine over time, as judged by the patients' local skin reactions following revaccination. Results of the study document a waning immunity to vaccinia immunization in the majority of re-vaccinees. Over 63.