Detection of vaccinia virus DNA, but not infectious virus, in the blood of smallpox vaccine recipients.

The authors of a recent study suggested that the duration of deferral for blood donations by smallpox vaccinees should be extended, based on detection of vaccinia virus DNA in 5 blood samples by PCR and the potential for viremia. We found that 4 of 202 blood specimens (from 3 of 27 smallpox vaccinees) were positive for vaccinia virus DNA by PCR; none were positive for virus by culture. Throat swabs were negative by PCR and culture. Thus, while some blood specimens contained vaccinia virus DNA, infectious virus was not detected. Current guidelines for deferral of blood donation in vaccinees seem appropriate.