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Herpes zoster incidence quadruples since 1945
Incidence of herpes zoster increased more than fourfold within the population of a Minnesota county over approximately 60 years, according to a recently published cohort study.
This long-term trend is consistent with changes reported over shorter study periods, and does not appear to be influenced by the introduction of varicella vaccination, antiviral therapy or growing immunocompromised populations.
“Herpes zoster (HZ) results from reactivation of varicella-zoster virus after a latency period following primary infection,” Kosuke Kawai, ScD, of the Clinical Research Center at Boston Children’s Hospital and Harvard Medical School, and colleagues wrote.
“Temporal increases in the incidence of HZ have been reported previously in the United States, Canada, United Kingdom, Spain, Japan, Taiwan and Australia. However, the majority of prior studies are limited to the last 2 decades and relatively short study periods of 5 to 10 years.”
Varicella vaccination shows no impact on overall incidence trends
Kawai and colleagues conducted a long-term study of HZ incidence within Olmsted County, Minnesota. Using previously published data and an index of patient records, they constructed a dataset of patients diagnosed with HZ from January 1945 through December 1960 and January 1980 through December 2007. Along with reviewing the records to confirm incident cases of HZ, the researchers conducted analyses to identify any relationships between temporal incidence trends and immune status, antiviral prescription or the introduction of the varicella vaccination program in 1996.
Kawai and colleagues identified 8,017 cases of HZ during the two study periods. The mean age of HZ patients was 51.8 years, and 58.7% were female. Approximately 35% received antiviral therapy, and 6.6% were immunocompromised.
After age and sex adjustment, HZ incidence increased from 0.76 per 1,000 person-years (95% CI, 0.63-0.89) from 1945 to 1949 to 3.15 per 1,000 person-years (95% CI, 3.04-3.26) from 2000 to 2007. The incidence increased for both sexes and all age groups, but the risk for HZ was greater in women vs. men and increased with age. Although there was no overall change in the rate of incidence increases after the introduction of varicella vaccination, there was a decline among children aged younger than 10 years (P < .0001).
According to the researchers, this is the longest study period examining HZ trends yet reported, and reinforces previous data suggesting an increase over shorter periods. However, they wrote, the findings offer no immediate explanations for the changes.
“This increase is unlikely to be due to the introduction of varicella vaccination, antiviral therapies or change in the prevalence of immunocompromised individuals,” they wrote. “The increasing incidence of HZ is a public health concern and more research is required to elucidate the underlying cause of the fourfold increase.”
HZ incidence decreases among HIV patients after ART
In contrast to HZ increases among the general population, findings published in 2015 suggest a significant decrease in incidence among HIV patients following the introduction of ART.
Sophie Grabar, MD, PhD, of the Institut Pierre Louis d’Epidémiologie et de Santé Publique in Paris, and colleagues evaluated HZ incidence and risk factors among patients with HIV who were followed from 1992 to 2011. They compared the incidence in this population with that of the general population from 2005 to 2008 and also evaluated the risk for herpes zoster among patients with HIV after initiating ART.
HZ was diagnosed in 7,167 patients during the period. The incidence rate declined significantly from 2,955 per 100,000 person-years in the pre-ART era (1992-1996) to 628 per 100,000 person-years in the recent ART era (2009-2011), and was explained by ART use (RR=0.6; 95% CI, 0.57-0.64). In an adjusted analysis, the risk was significantly higher between 3 months and 6 months of treatment (RR=1.39; 95% CI, 1.16-1.66). After adjusting for sex and age, risk for HZ was 2.7 times greater among those with HIV than the general population from 2005 to 2008.
“The overall decrease in the incidence of herpes zoster among HIV-infected patients in the ART era is probably related to improved immune restoration and viral control,” Grabar and colleagues wrote. “This trend may continue in the future as ART is initiated earlier and at higher CD4 cell counts, as recommended by most recent guidelines.” – by Dave Muoio
Disclosure: Kawai reports previously being a consultant for Merck. Please see the full studies for a list of all other authors’ relevant financial disclosures.