Herpes zoster virus continues to be prevalent in certain patient demographics in the United States, according to a study recently published in Clinical Infectious Diseases. Incidence of the disease remains unpredictable despite positive associations with age and sex.

This prospective study included data on 27,262,603 individuals, which was sourced from Truven Health Marketscan population tables (1993-2015) and enrollment tables (1998-2016). The 2 datasets were aggregates that included maximum possible lookback, and all participants were aged >35 years old. Disease incidence was computed as annual age-specific incident cases divided by the annual Marketscan population adjusted for age. The association of sex and age with incidence of herpes zoster was analyzed using a generalized linear model of multivariate analysis with log link function and binomial distribution. Correlation between variance in herpes zoster and age was examined with the Pearson Chi-square test.

The follow-up period in this study had a median of 49 months (interquartile range, 24-85). Herpes zoster was diagnosed in 934,340 individuals in the population tables and 804,029 in the enrollment tables, 92% of which matched the primary diagnostic code. Women constituted 62% of cases, and the mean age at diagnosis were 59.4 years and 59.3 years in the two groups. Herpes zoster incidence was significantly associated with being female, with a relative incidence rate of 1.38 (95% CI, 1.38-1.39; P<.0001). Between 1993 and 2006, the incidence of herpes zoster increased from 2.5/1000 to 6.1/1000 and to 7.2/1000 in 2016. The incidence stratified by age, and demonstrated that older age associated with higher rates of disease.

Limitations to this study included a convenience sample that may not fully represent the population, as well as a lack of control for patients who are immunocompromised, chronic conditions, or healthcare practices. In addition, data on zoster vaccine live was not incorporated into this research.

The study researchers concluded that “[there] are an estimated million episodes of [herpes zoster] annually in the US, often causing significant pain, suffering and disability. This substantial burden provides rationale for continuing to monitor patterns of [herpes zoster] incidence. Fortunately, vaccines are now available to reduce that [herpes zoster] burden. Nonetheless, given the seeming unpredictability of [herpes zoster] incidence over time, researchers and public health practitioners need to be cautious in interpreting or attributing those patterns.”

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Reference

Harpaz R, Leung JW. The epidemiology of herpes zoster in the United States during the era of varicella and herpes zoster vaccines: Changing patterns among children [published online November 29, 2018]. Clin Infect Dis. doi: 10.1093/cid/ciy954