Using combined data from 6 integrated healthcare organizations from 2003 through 2014, researchers found a decline in pediatric herpes zoster incidence and a significantly lower incidence among vaccinated children, according to study results published in Pediatrics.

Electronic health records for children aged ≤17 years were used to identify cases of herpes zoster and to calculate zoster incidence rates per 100,000 person-years of health plan membership for all children and among those who were vaccinated compared with those who were unvaccinated. More than 6 million children with ≥1 month of health plan membership were included.

The crude herpes zoster incidence rate over 12 years for all subjects was 74 per 100,000 person-years. The rate among children who received a varicella vaccine was 38 per 100,000 person-years, which was 78% lower compared with children who were unvaccinated (170 per 100,000 person-years; P <.0001). Of note, the herpes zoster incidence rate was 5- to 6-times higher for children with immunosuppression compared with those who did not have immunosuppression. By 2014, the herpes zoster incidence rate overall also declined to an all-time low of 72% (P <.0001). During the study period, annual incidence rates were always lower for vaccinated children than for those who were unvaccinated.

The study results also demonstrated a possible association of early vaccination with an increased risk for herpes zoster developing. Stratification by age of herpes zoster diagnosis showed that children aged 1 year who were vaccinated had a 140% higher risk for incident infection compared with children of the same age who were unvaccinated. However, this increased risk was no longer apparent after age 2 years, and by age 5 to 17 years, the incidence rates of herpes zoster were much lower in those who were vaccinated compared with those who were not.

The study was limited by the lack of data regarding prevaccine era herpes zoster rates for this population; the investigators were also unable to calculate information on herpes zoster rates by ethnicity. In addition, the varicella vaccination requirements varied by state in this study, and serologic or medical record evidence was not available to calculate the underlying herpes zoster risk in unvaccinated groups. The retrospective nature of the study also prohibited herpes zoster virus typing. The dataset was also limited to children who sought medical care. Confirmation of cases through polymerase chain reaction testing was also not done, which may have resulted in inclusion of non-herpes zoster-related rashes. However, a previously derived laboratory confirmation adjustment was applied. The study authors also noted that their classification of children as having immunosuppression using International Classification of Diseases-9th edition codes was conservative.

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According to the investigators, these data reinforce the benefits of varicella vaccination for herpes zoster prevention. The overall risk for herpes zoster is significantly lower in vaccinated children compared with unvaccinated children, and incidence was lower in children receiving 2 as opposed to 1 dose of the varicella vaccine. The investigators also believe that it is possible herpes zoster rates may be “lower than reported here during a maturing 2-dose varicella vaccination program.”

Reference

Weinmann S, Naleway AL, Koppolu P, et al. Incidence of herpes zoster among children: 2003-2014. Pediatrics. 2019;144:e20182917.