Virus present up to one month after Zostavax immunization

Some patients inoculated with Zostavax, Merck's shingles vaccine, shed the virus used for the vaccine through their saliva for one month after immunization, according to a researcher from the University of Texas, Houston. Zostavax uses a live accentuated varicella zoster virus to provide protection from shingles, and in January, a retrospective study showed it halved the risk of developing shingles, leading the CDC to recommend all adults over 60 receive the vaccine.

However, says Dr. Catherine DiGiorgio, researchers don't yet know if the varicella virus being shed in saliva and at inoculation sites after immunization is infectious. Despite the potentially sour news, there could be an upside. "It possibly could have use in clinical practice, allowing detection of shingles prior to development of the rash, enabling earlier start of antiviral therapy, and decreasing the duration of shingles and the pain of post-herpetic neuralgia," DiGiorgio said.

In a prospective study, researchers found virus DNA on saliva swabs of more than half of the subjects--21 to be exact--10 minutes after vaccination. Two patients still had varicella DNA on their swabs 28 days after inoculation. Merck's varicella zoster virus is also used in the company's chicken pox vaccine, and there are documented cases of indirect infection from contact with recently vaccinated individuals.

- read the Internal Medicine News article