The impact of varicella vaccination on paediatric herpes zoster epidemiology: a Canadian population-based retrospective cohort study

Abstract

The impact of universal varicella vaccination on herpes zoster (HZ) risk in unvaccinated and vaccinated children, and its long-term influence on HZ epidemiology, remains unknown. We conducted a retrospective cohort study using population-based administrative health data for children born between 1993 and 2018 (n = 924,124). We calculated age-specific cumulative HZ incidence rates by vaccination status for cohorts born before (1993–1999) and after (2000–2018) programme implementation; results were used to calculate relative risk of HZ by age group, vaccination status and vaccine availability period. Annual HZ incidence rates were calculated for 1993–2018. HZ risk was higher among unvaccinated children compared to vaccinated children across age groups; 64% higher before universal vaccination (RR: 0.36, 95% CI: 0.33, 0.39), and 32% higher after universal vaccination (RR: 0.68, 95% CI: 0.64, 0.73). Among unvaccinated children, HZ risk was 60% lower after vaccine programme implementation (RR: 0.40, 95% CI: 0.38, 0.43). Two-dose receipt corresponded with a 41% lower risk of HZ compared to one-dose receipt (RR: 0.59, 95% CI: 0.53, 0.65). Crude annual HZ incidence rates declined 64% after programme implementation, with decreases observed across age groups. Universal varicella vaccination programme implementation corresponds to decreased paediatric HZ incidence across age groups, in both vaccinated and unvaccinated individuals. Results from this study can be used to help inform varicella vaccination programme decision-making in other countries.

Herpes zoster: A Review of Clinical Manifestations and Management

“…While HZ is uncommon among children, the HZ risk could be diminished by 64% in children after vaccination for varicella, as shown in a Canadian study. Varicella vaccination in the youth does not seem to reduce HZ risk during aging [6].…”

Trend in the Numbers of Hospitalized Patients With Varicella, Herpes Zoster, and Ischemic Stroke in Japanese Individuals <20 Years of Age Before and After Implementation of Universal Varicella Vaccination

“…Over the years after the introduction of universal varicella vaccination, the number of pediatric cases of HZ gradually declined. 10 In this study, the number of hospitalizations for HZ in patients <20 years of age did not change throughout the observation period. As shown in Figure 1B, HZ is more common in those 5 years of age and older.…”

Epidemiology of Herpes Zoster in the pre-vaccination era: establishing the baseline for vaccination programme’s impact in Spain

“…Age interacted with other factors; mortality risk was higher at an older age but lower in older age groups once adjusted for comorbidities and sex. Although age seems to be the most important risk factor for the development of HZ, an immunocompromised state at the onset of HZ may have a significantly higher rate of complications [27,42,43], which would support the risk groups being included in the current vaccination policies. As pointed out above, underlying mechanisms contributing to these phenomena may be immunosenescence, and a higher presence of some haematological neoplasms at a lower age [22,37].…”