Q: I have a patient who is taking acyclovir long-term to prevent herpes simplex keratitis outbreaks with good suppression. She is 62 years old, so her primary-care practitioner has recommended that she get the zoster vaccine. Because this is a live virus vaccine, do I need to stop her viral medication due to possible suppression?

Licensed antiviral medications active against members of the herpes virus family include acyclovir, famciclovir and valacyclovir. These agents might interfere with replication of the live, varicella zoster virus-based vaccine, says Jay S. Pepose, M.D., Ph.D., of St. Louis.

All three agents have relatively short serum half-lives and are quickly cleared from the body, he says. People taking chronic acyclovir, famciclovir or valacyclovir should discontinue these medications at least 24 hours before administration of the zoster vaccine, if possible.1

And, the medications should not be used for at least 14 days after vaccination, by which time the immunologic effect should be established, Dr. Pepose adds.1

In a European clinical trial, the varicella zoster virus-based vaccine reduced the burden of illness in 61% of individuals over the age of 60 and reduced the incidence of postherpetic neuralgia by 67%. Subjects in this trial were 51% less likely than the controls to develop zoster.2

Two different forms of anterior herpes simplex infection: immune or necrotizing stromal keratitis (left), and dendritic or geographic epithelial keratitis.
Photos courtesy: Jay S. Pepose, M.D., Ph.D.

Q: What are her chances of having an outbreak of herpes simplex keratitis?

If the patient resumes her regimen of acyclovir, she should be less likely to develop an outbreak. With regard to the effect of stopping the acyclovir on the likelihood of recurrence, the effect of prophylactic acyclovir on epithelial keratitis and stromal keratitis was similar, and it reduced recurrence by around 45%, says Dr. Pepose.3 

When she discontinues the antiviral medication, the patient should be counseled to call if there are signs suggestive of recurrent herpetic keratitis, such as injection, irritation or decreased vision, adds Dr. Pepose. An office visit during the few weeks she is off acyclovir may be prudent.3

In the study, acyclovir did not prevent the original occurrence of stromal keratitis, but it did prevent recurrences, he says. But, for both epithelial keratitis and stromal keratitis, the chances of further recurrence increased with each bout that occurred, adds Dr. Pepose.3

And, after treatment, the recurrence rate was similar in both the acyclovir and the placebo group. No rebound effect was seen, Dr. Pepose says.3


1. The Centers for Disease Control and Prevention. General Recommendations on Immunization: Recommendations of the Advisory Committee on Immunization Practices. MMWR 2006;55(No. RR-15). Available at: www.cdc.gov/mmwr/preview/mmwrhtml/rr5515a1.htm (Accessed April 14, 2009).

2. Wutzler P. Herpes zoster and postherpetic neuralgiaprevention by vaccination? Dtsch Med Wochenschr 2009 Apr;134(Suppl 2):S90-4.

3. Herpetic Eye Disease Study Group. Acyclovir for the prevention of recurrent herpes simplex virus eye disease. N Engl J Med 1998 Jul 30;339(5):300-6.

Vol. No: 146:05Issue: 5/15/2009