Trends in hospitalizations with primary varicella and herpes zoster during the prevaricella and initial postvaricella and herpes zoster vaccine eras, connecticut, 1994-2012

Epidemiological Impact and Cost-Effectiveness of Varicella Vaccination Strategies in the United Kingdom

Background

Despite the burden of varicella, there is no universal varicella vaccination (UVV) program in the United Kingdom (UK) due to concerns that it could increase herpes zoster (HZ) incidence. We assessed the cost-utility of a first-dose monovalent (varicella [V]) or quadrivalent (measles-mumps-rubella-varicella [MMRV]) followed by a second-dose MMRV UVV program. GSK and MSD varicella-containing vaccines (VCVs) were considered.

Methods

Dynamic transmission and cost-effectiveness models were adapted to the UK. Outcomes measured included varicella and HZ incidences and the incremental cost-utility ratio (ICURs) over a lifetime horizon. Payer and societal perspectives were evaluated.

Results

The impact of V-MMRV and MMRV-MMRV UVV programs on varicella incidence was comparable between both VCVs at equilibrium. HZ incidence increased by 1.6%–1.7% over 7 years after UVV start, regardless of the strategies, then decreased by >95% at equilibrium. ICURs ranged from £5665 (100 years) to £18 513 (20 years) per quality-adjusted life-year (QALY) gained with V-MMRV and from £9220 to £27 101 per QALY gained with MMRV-MMRV (payer perspective). MMRV-MMRV was cost-effective in the medium- and long-terms with GSK VCV and only cost-effective in the long term with MSD VCV at a £20 000 per QALY gained threshold. Without the exogenous boosting hypothesis, HZ incidence decreased through UVV implementation. ICURs were most sensitive to discount rates and MMRV price.

Conclusions

A 2-dose UVV was demonstrated to be a cost-effective alternative to no vaccination. With comparable effectiveness as MSD VCV at lower costs, GSK VCV may offer higher value for the money.

Incidence of Hospitalizations and Emergency Department Visits for Herpes Zoster in Immunocompromised and Immunocompetent Adults in Ontario, Canada, 2002-2016

BACKGROUND

Immunocompromised adults are at .increased risk of herpes zoster (HZ) infection and related complications. We aimed to assess the incidence of hospital-attended HZ (ie, seen in hospital or emergency department) in immunocompromised populations and compare it to immunocompetent populations.

METHODS

We calculated incidence rates (IRs) of hospital-attended HZ in Ontario, Canada, between 1 April 2002 and 31 August 2016 in adults ≥18 years of age categorized as immunocompromised or immunocompetent. We repeated these analyses by type of immunocompromising condition and provided incidence rate ratios (IRRs) comparing to immunocompetent adults. We also calculated IRs and IRRs of HZ complications by immunocompromised status.

RESULTS

There were 135 206 incident cases of hospital-attended HZ during the study period. Immunocompromised adults accounted for 13% of these cases despite representing 3% of the population. The risk of hospital-attended HZ was higher for immunocompromised adults compared with immunocompetent adults (IRR, 2.9 [95% confidence interval {CI}, 2.9-3.0]) and ranged across type of immunocompromising conditions, from 2.6 (95% CI, 2.6-2.7) in those with a solid tumor malignancy to 12.3 (95% CI, 11.3-13.2) in those who had undergone hematopoietic stem cell transplant. The risk of any HZ complication was higher in immunocompromised adults (IRR, 3.6 [95% CI, 3.5-3.7]) and highest for disseminated zoster (IRR, 32.8 [95% CI, 27.8-38.6]).

CONCLUSIONS

The risk of hospital-attended HZ and related complications was higher in immunocompromised populations compared with immunocompetent populations. Our findings underscore the high-risk nature of this population and the potential benefits that may be realized through HZ vaccination.

Herpes zoster in older adults in Ontario, 2002-2016: Investigating incidence and exploring equity

Older adults are at increased risk of herpes zoster (HZ) and post-herpetic neuralgia (PHN) and HZ vaccines are available to help prevent infection. The objective of our study was to provide updated data on incidence of HZ and PHN related to clinical and demographic factors in older adults to inform immunization practices. We conducted a population-based, retrospective cohort study and included all cases of HZ seen in outpatient, emergency department, and hospital settings for adults aged 65 years and over between April 1, 2002 to August 31, 2016 in Ontario, Canada. We calculated the incidence of HZ and PHN, and estimated the proportion within each subgroup that developed PHN. We also assessed incidence by neighbourhood-level income quintile before and after the availability of vaccine for private purchase. The average annual incidence of HZ in any setting was 59.0 per 10,000 older adults, with higher incidence in outpatient as opposed to hospital settings. Incidence was higher in the oldest age groups, females, and those classified as immunocompromised or frail. Relative to the pre-vaccine era, the disparities in incidence of HZ by neighbourhood-level income increased, with higher rates of HZ and PHN seen in those residing in lower income quintiles. Additional prevention efforts should be targeted toward adults who are immunocompromised, frail, and those living in lower socioeconomic quintiles. Future work should assess the impact of the zoster vaccine program with a particular focus on equity in the publicly-funded era.

The Impact of Varicella Vaccination on the Incidence of Varicella and Herpes Zoster in the United States: Updated Evidence From Observational Databases, 1991-2016

BACKGROUND

Universal childhood vaccination against varicella began in the United States as a 1-dose schedule in 1996, changing to a 2-dose schedule in 2006. The exogenous boosting hypothesis, which postulates that reexposure to circulating wild-type varicella delays the onset of herpes zoster, predicts a transient increase in the incidence of herpes zoster, peaking in adults 15-35 years after the start of varicella vaccination.

METHODS

This was a retrospective study of administrative claims data from the MarketScan Commercial and Medicare databases between 1991-2016. Outcome measures were the incidences of herpes zoster per 100 000 person-years, by calendar year and age category, and the annual rates of change in herpes zoster by age category, in an interrupted time series regression analysis, for the periods of 1991-1995 (prevaccine), 1996-2006 (1-dose vaccination period), and 2007-2016 (2-dose vaccination period).

RESULTS

The annual incidences of herpes zoster increased throughout the period of 1991-2012 in all adult age categories, with a plateau in 2013-2016 that was most evident in the ≥65 age group. In 1991-1995, the herpes zoster incidences increased at annual rates of 4-6% in age categories 18-34, 35-44, 45-54, and 55-64 years. In the same age categories during 1996-2006 and 2007-2016, the herpes zoster incidences increased at annual rates of 1-5%.

CONCLUSIONS

Although the annual incidence of herpes zoster in adults has continued to increase, the rates of change decreased during both the 1- and 2-dose vaccination periods. The hypothesized increase in herpes zoster predicted from modelling of the exogenous boosting hypothesis was not observed.

The Epidemiology of Herpes Zoster in the United States During the Era of Varicella and Herpes Zoster Vaccines: Changing Patterns Among Children

Varicella vaccination can have complex direct and indirect influences on the epidemiology of herpes zoster among children. We evaluated pediatric herpes zoster trends using administrative databases. The incidence has declined in a step-wise pattern since the varicella vaccination program's introduction, suggesting that rates may eventually decline in the entire population.

Do varicella vaccination programs change the epidemiology of herpes zoster? A comprehensive review, with focus on the United States

Introduction: Policy-makers in many countries have been wary of introducing varicella vaccination programs because of concerns that reduced exposures to varicella-zoster virus could increase herpes zoster (HZ) incidence. The U.S. introduced varicella vaccination in 1996 and has empiric evidence regarding this concern. Areas covered: This comprehensive review provides background emphasizing the epidemiology of varicella and of HZ in the U.S. before and after the introduction of their respective vaccines. The epidemiology is complex, and interpretation is complicated by methodologic challenges, by unexplained increases in age-specific HZ incidence that preceded varicella vaccination, and by introduction of vaccines for prevention of HZ. Nonetheless, observations from studies using different platforms and designs have yielded consistent findings, suggesting they are robust. Expert opinion: There has been no evidence that the U.S. varicella vaccination program increased HZ incidence in the general adult population over baseline trends. Furthermore, HZ incidence in children is declining. The U.S. experience can inform the development of new generations of models to predict HZ trends. More importantly, it provides reassurance for countries considering varicella vaccination that an effective program can reduce varicella morbidity and mortality while reducing the likelihood of HZ among children, and potentially, over time, across the entire population.

Trends in U.S. Community hospitalizations due to herpes zoster: 2001-2015

BACKGROUND

In 2007, based on decisions by the U.S. Advisory Committee on Immunization Practices, the CDC recommended a booster dose at 4-6 years in the varicella vaccine schedule. In 2008, a herpes zoster vaccine was recommended for use in persons age ≥60 years. The purpose of this study was to examine trends in herpes zoster hospitalization rates and assess the impact of both policy recommendations using U.S. hospital discharge data.

METHODS

Nationwide Inpatient Sample discharge data from 2001 to 2015 were used to identify primary or secondary herpes zoster diagnoses. Trends in annual total and age-specific herpes zoster hospitalization rates and average length of stay were examined. Average annual rates for the pre (2001-2005) and post (2012-2015)-zoster vaccine policy eras were compared. Absolute change in herpes zoster hospitalizations were calculated.

RESULTS

The rate difference of U.S. herpes zoster hospitalizations in the post vs. pre-zoster vaccine policy era was -1.9 per 100,000 population (6,200 fewer hospitalizations in 2015 than expected). Key age group rate differences: 0-3 years (-0.4 per 100,000; 50 fewer), 4-6 years (-0.6 per 100,000; 50 fewer), 7-14 years (-1.3 per 100,000; 400 fewer), 50-59 years (0.7 per 100,000; 300 more), 60-69 years (-2.5 per 100,000; 900 fewer), 70-79 years (-10.2 per 100,000; 2,000 fewer), 80+ years (-29.9 per 100,000; 3,600 fewer).

CONCLUSIONS

Reduction of wild-type varicella due to the 2-dose varicella vaccination recommendation may have impacted declining herpes zoster hospitalization rates among children ≤14 years. The 2008 herpes zoster vaccine may have impacted declining herpes zoster hospitalization rates for adults age ≥60 years despite vaccination coverage <31% by 2015.

Systematic Review and Meta-analysis of Chickenpox Vaccination and Risk of Herpes Zoster: A Quantitative View on the “Exogenous Boosting Hypothesis”

Background

The “exogenous boosting hypothesis” postulates that reexposure to circulating varicella zoster virus (VZV) over the life span inhibits reactivation of VZV. Consequently, if circulation of VZV is suppressed by introduction of chickenpox vaccination, incidences of herpes zoster may rise.

Methods

We performed a systematic review and metaanalysis on impact of chickenpox vaccination on herpes zoster incidence and time trend, focusing on population-level effects by analyzing interrupted time-series (ITS) studies. We searched Medline and Embase for ITS reporting incidences of chickenpox and herpes zoster before and after implementation of chickenpox vaccination. Autoregressive integrated moving average models were calculated. Change in trend and incidence from studies were pooled.

Results

Twelve studies were included, of which 6 were eligible for metaanalysis. Metaanalysis revealed a significant increase in chickenpox cases prior to implementation of chickenpox vaccination and a reversed trend thereafter, particularly in individuals aged 1–4 years. The increase in age-adjusted herpes zoster incidence before implementation of chickenpox vaccination did not change thereafter. However, separate analysis of age groups revealed a net increase of hospitalized herpes zoster cases in individuals aged 10–49 years after implementation of chickenpox vaccination. This very small effect (fewer than 2 additional cases per 100 000 persons) did not occur in other age groups.

Conclusions

To date, no conclusive evidence exists that chickenpox vaccination has a substantial population-level impact on herpes zoster in nonvaccinated age groups. While exogenous boosting may exist, the effect size generated by chickenpox vaccination might be rather small on the population level.

Evaluation of the effect of chickenpox vaccination on shingles epidemiology using agent-based modeling

BACKGROUND

Biological interactions between varicella (chickenpox) and herpes zoster (shingles), two diseases caused by the varicella zoster virus (VZV), continue to be debated including the potential effect on shingles cases following the introduction of universal childhood chickenpox vaccination programs. We investigated how chickenpox vaccination in Alberta impacts the incidence and age-distribution of shingles over 75 years post-vaccination, taking into consideration a variety of plausible theories of waning and boosting of immunity.

METHODS

We developed an agent-based model representing VZV disease, transmission, vaccination states and coverage, waning and boosting of immunity in a stylized geographic area, utilizing a distance-based network. We derived parameters from literature, including modeling, epidemiological, and immunology studies. We calibrated our model to the age-specific incidence of shingles and chickenpox prior to vaccination to derive optimal combinations of duration of boosting (DoB) and waning of immunity. We conducted paired simulations with and without implementing chickenpox vaccination. We computed the count and cumulative incidence rate of shingles cases at 10, 25, 50, and 75 years intervals, following introduction of vaccination, and compared the difference between runs with vaccination and without vaccination using the Mann-Whitney U-test to determine statistical significance. We carried out sensitivity analyses by increasing and lowering vaccination coverage and removing biological effect of boosting.

RESULTS

Chickenpox vaccination led to a decrease in chickenpox cases. The cumulative incidence of chickenpox had dropped from 1,254 cases per 100,000 person-years pre chickenpox vaccination to 193 cases per 100,000 person-years 10 years after the vaccine implementation. We observed an increase in the all-ages shingles cumulative incidence at 10 and 25 years post chickenpox vaccination and mixed cumulative incidence change at 50 and 75 years post-vaccination. The magnitude of change was sensitive to DoB and ranged from an increase of 22-100 per 100,000 person-years at 10 years post-vaccination for two and seven years of boosting respectively (p < 0.001). At 75 years post-vaccination, cumulative incidence ranged from a decline of 70 to an increase of 71 per 100,000 person-years for two and seven years of boosting respectively (p < 0.001). Sensitivity analyses had a minimal impact on our inferences except for removing the effect of boosting.

DISCUSSION

Our model demonstrates that over the longer time period, there will be a reduction in shingles incidence driven by the depletion of the source of shingles reactivation; however in the short to medium term some age cohorts may experience an increase in shingles incidence. Our model offers a platform to further explore the relationship between chickenpox and shingles, including analyzing the impact of different chickenpox vaccination schedules and cost-effectiveness studies.

The changing epidemiology of varicella and herpes zoster in Hong Kong before universal varicella vaccination in 2014

In Hong Kong, universal varicella vaccination started in July 2014. Before this, children could receive varicella vaccine via the private market. We analysed the epidemiology of varicella and zoster before universal vaccination. We estimated varicella vaccination coverage through surveys in preschool children. We estimated the burden of varicella and zoster with varicella notifications from 1999/00 to 2013/14, Accident and Emergency Department (A&E) attendance and inpatient admissions to public hospitals from 2004/05 to 2013/14. We fitted a catalytic model to serological data on antibodies against varicella-zoster virus to estimate the force of infection. We found that varicella vaccination coverage gradually increased to about 50% before programme inception. In children younger than 5 years, the annual rate of varicella notifications, varicella admission and zoster A&E attendance generally declined. The annual notification, A&E attendance and hospitalisation rate of varicella and zoster generally increased for individuals between 10 and 59 years old. Varicella serology indicated an age shift during the study period towards a higher proportion of infections in slightly older individuals, but the change was most notable before vaccine licensure. In conclusion, we observed a shift in the burden of varicella to slightly older age groups with a corresponding increase in incidence but it cannot necessarily be attributed to private market vaccine coverage alone. Increasing varicella vaccination uptake in the private market might affect varicella transmission and epidemiology, but not to the level of interrupting transmission.

Temporal trends in herpes zoster-related hospitalizations in Italy, 2001-2013: differences between regions that have or have not implemented varicella vaccination

BACKGROUND

Herpes zoster (HZ) has a relevant impact on the population in terms of incidence and complications.

AIMS

The aim of this study was to estimate the HZ-related hospitalization rates in Italy in the period 2001-2013, and to evaluate the trend of hospitalizations in the course of time pointing out any differences between regions that have or have not introduced universal childhood varicella immunization (UVI).

METHODS

A retrospective analysis was conducted on hospital discharge records contained in the national database of the Ministry of Health for the period January 2001-December 2013. The comparison of hospitalization rates of "pilot" versus "not pilot" regions was performed taking into account as "pilot" regions the three that first introduced UVI (Sicily, Veneto, and Apulia). The average annual percentage change in hospitalization rates was used to highlight any significant change in time trends.

RESULTS

In the period 2001-2013, 93,808 HZ-related hospitalizations were registered altogether. Complicated HZ was diagnosed in 53.2% of cases; a relevant part (32.5%) of hospitalizations involved subjects with at least one co-morbidity. In the three Italian "pilot" regions, a greater decrease of HZ-related hospitalization rates occurred in comparison to other regions.

DISCUSSION

A good understanding of the epidemiology of HZ disease is required to assess the overall impact of the varicella immunization programs and to establish the most appropriate health strategies against HZ.

CONCLUSIONS

The data obtained confirm the epidemiological impact of HZ and its complications and the need of a preventive approach.

Varicella vaccination - the global experience

INTRODUCTION

Varicella, although a frequently benign childhood disease, nevertheless represents a considerable health burden. WHO recommends including varicella vaccines in universal routine vaccination programs, and maintaining coverage >80%. Many countries have successfully introduced varicella vaccination and have benefited from lower disease burden, but many others have not adopted the vaccine. Reasons include cost commitment for a 'mild childhood disease' or concerns that vaccination will shift varicella to older age groups or increase herpes zoster incidence. Areas covered: This literature review summarizes the effectiveness and epidemiological impact of varicella immunization programs. Expert commentary: Varicella vaccines are immunogenic with acceptable safety profiles. One and two dose schedules are highly effective against varicella and large reductions in disease incidence, particularly moderate-severe disease, have been widely reported. There is currently no evidence to suggest that the introduction of varicella vaccination results in a shift of varicella disease burden to older age groups. Although epidemiological studies have shown an increased incidence of herpes zoster since the vaccines were launched, there are many other contributing factors, and indeed, this secular trend was evident before their introduction. In conclusion, varicella vaccination easily fits into existing immunization programs and significantly reduces the often underestimated burden of varicella.