The incidence of herpes zoster (shingles) in veterans seeking care at VA hospitals continues its steady increase, rising even since a 2010 report documented a near doubling of the rate using VHA Decision Support System data from 2000 to 2007.
Incidence rates among VA patients, who are typically older, provide an indication of likely trends in the general population as herpes zoster occurs at a higher rate among adults over the age of 60, a rapidly expanding group in the United States.
The research, published in Clinical Infectious Diseases in 2010, reflected national data through 2007 and showed a rise from 3.1 episodes per 1,000 in 2000 to 5.2 cases per 1,000 in 2007.
“Data through 2010 show the trend continuing at the same rate,” said David Rimland, MD, Chief, Infectious Diseases, at the VAMC in Atlanta and lead author of “Increasing Incidence of Herpes Zoster among Veterans.” “We have seen a gradual, but persistent, increase across all age groups to about six cases per 1,000 in the VA population in care since that study,” Rimland noted.
Previous research had indicated a rate of 1.2-4.8 cases of herpes zoster per 1,000 in all immunocompetent adults, rising to 7.2-11.8 cases per 1,000 for immunocompetent adults age 60 or older, with a lifetime risk of 10% to 20%.
The research done by Rimland and Abeer Moanna, MD, showed an especially notable increase in the incidence of zoster among those aged 50 or older over the study period.Their study noted that the total number of veterans with a herpes zoster diagnostic code in the VA system increased from 24,269 to 47,658 in the 2000 to 2007 time period.
Herpes zoster results from reactivation of the virus that causes chicken pox. After chicken pox infection, the virus persists in a dormant state in clusters of sensory nerve cells. The virus can reactivate, multiply and damage sensory nerve cells as aging weakens immune systems.
Vaccine Adoption Rates Low
Despite the morbidity of the disease, which can include a painful rash, blisters, sensitivity to touch and postherpetic neuralgia (PHN), the herpes zoster vaccine has had minimal uptake in the VA and general populations. The vaccine, Zostavax® was introduced by Merck & Co. Inc. in 2007.
“Less than 2% of eligible veterans have gotten the vaccine,” said Rimland. “It could be an informational or a logistics issue. The vaccine must be kept frozen until it’s administered, and a lot of CBOCs (community-based outpatient clinics) do not have freezers. Veterans used to have to request the vaccine through the pharmacy and then go to a specific clinic to get it.”
To increase accessibility, VA is adding freezers to many CBOCs to store the vaccine, which must be kept at 5° F or -15° C. In addition, it is trying to raise awareness of the vaccine nationally to boost the number of veterans protected against herpes zoster, Rimland said.
“We want to get out more information about how to get the vaccine and who should get it. The CDC recently dropped the recommended age for the vaccine from age 60 to 50, increasing the population potentially eligible,” said Rimland.
In the general population, uptake of the vaccine is similar, at 1.9%. “Cost is not an issue among veterans, but it may be among others,” said Rimland.
Initial testing of Zostavax® showed protection against herpes zoster of 50%, an efficacy rate confirmed by a later study among veterans.
A study published in January of this year in the Journal of the American Medical Association found that vaccination reduced risk about 55%, regardless of age race or co-morbidities.
Noting that approximately 1 million cases of herpes zoster occur in the United States annually,
Hung Fu Tseng, PhD, MPH, of Southern California Kaiser Permanente, Pasadena, and colleagues evaluated the risk of herpes zoster in more than 75,000 vaccinated adults—all community-dwelling, age 60 and older and members of a managed-care organization. They were matched with more than 227,000 unvaccinated members in a similar cohort.
“It’s not as good as some of the childhood vaccines, where we’re used to seeing 80-90% efficacy,” observed Rimland.
But protecting half of those who receive the vaccine is better than other options. “There isn’t a great approach, in terms of treatment. The acute episode is not pleasant, but if it went away, it would be better. Some people have postherpetic neuralgia for years, so reducing the incidence is very important,” said Rimland.
Up to one-third of patients who develop herpes zoster after age 60, and about 20% of all adults with the disease, suffer from postherpetic neuralgia, which can be very painful. The herpes zoster (HZ) vaccine reduces the incidence of PHN by 67%, according to the Shingles Prevention Study, a 5 ½-year study conducted by the VA in conjunction with other federal agencies and Merck.
“Even without complications, HZ can interfere with an elderly patient’s ability to perform essential activities of daily living, resulting in a loss of independence that is emotionally devastating and frequently irreversible,” the Shingle Prevention Study authors said in their study’s purpose statement. “The most common complication of HZ in elderly persons is postherpetic neuralgia (PHN), which frequently results in disordered sleep, chronic fatigue, anxiety and severe depression. Antiviral therapy has a modest impact on the acute phase of HZ. However, it does not appear to prevent the development of PHN.”
Varicella Vaccine and Herpes Zoster
No one knows for sure why herpes zoster is on the rise. One theory is that the varicella vaccine, introduced in 1995, has indirectly reduced natural immunity in older people. “As fewer kids get chicken pox, fewer adults are exposed. That exposure may boost immunity in older people, so we’re losing some of that natural immunity,” explained Rimland.
A mathematical model developed by Brisson, Gay, Edmunds and Andrews in 2002 predicted a substantial increase in the incidence of zoster for 30-50 years following broad adoption of varicella vaccination. Subsequent studies have supported this predicted increase.
The data are not unequivocal, however, as two studies of large health maintenance organizations have not found a similar correspondence between the decrease in the incidence of varicella and an increase in herpes zoster rates. Those studies looked at incidence rates for up to seven years after the introduction of the varicella vaccine, while the research using VHA data spanned 11 years.
Ultimately, the varicella vaccine will help older adults, too, noted Rimland.
“As today’s children get older, you’ll have adults who were protected by vaccine from chicken pox and so do not develop zoster.” That may take some time, however, as current teenagers now were the first to receive the vaccine.
Other possible explanations for increasing rates of herpes zoster could be moderate immunosuppression secondary to diseases or immunosuppressive agents, Rimland and Moanna said in their conclusions, noting that in one study of patients with rheumatoid arthritis at VAMCs, patients who were receiving TNF inhibitors were at the greatest risk of developing herpes zoster.