For decades, medical wisdom about shingles has been that it's a once-in-a-lifetime experience. The commonly-held belief is that patients are protected from a recurrence of the herpes zoster virus, which causes shingles, after one episode. But according to a study published in the February issue of Mayo Clinic Proceedings, recurrences of shingles may be significantly more common than doctors have suspected.
"It's been thought that recurrences were limited to people with compromised immune systems, for instance from chemotherapy or bloodborne malignancies, but this is not the case," says lead author Barbara Yawn, M.D., director of research at Olmsted Medical Center in Rochester. "Recurrence was prevalent in the immunocompetent population. We were very surprised by the results."
The research team examined medical records, dating from 1996 to 2001, of nearly 1,700 patients over age 22 who had a documented episode of shingles. The condition causes a specific type of skin rash and severe pain. They then searched area medical records to determine whether those patients had been treated for a second episode at any point, following them up to 12 years (the average follow-up was eight years). The data showed the recurrence rate was over 5 percent, the same rate an age-matched cohort would be expected to experience a first case of shingles. Some patients had experienced as many as three recurrences. "And that's only within eight years," Dr. Yawn notes. "As you continue to follow these patients throughout their lives, it's likely the recurrence rate will be much higher than 5 percent."
The study found that women, who are more likely than men to have shingles, also were more likely to experience a recurrence of the disease. Although the team had suspected that recurrence rates would be higher in older patients, age did not appear to make individuals more susceptible to another round of the disease. Instead, researchers found the most striking determinant for recurrence was patients' pain during the initial episode. Those who had experienced pain lasting more than 30 days after the initial onset of shingles were more likely to face a recurrence, particularly in the first three to four years after the initial episode. This, too, surprised the research team. "We'd thought that suffering a worse case would possibly give patients more resistance to a second occurrence, but our data presented the exact opposite," says Dr. Yawn.
The results suggest that the herpes zoster vaccine, which is known to reduce first-time occurrences of shingles by 50 percent, may help patients avoid a second episode. "Until now, we haven't been able to tell patients their risks of getting zoster a second time," Dr. Yawn says. "This study offers another piece of information for patients and doctors who are discussing the likelihood of recurrence and considering a prevention strategy."