Herpes zoster in Australia: evidence of increase in incidence in adults attributable to varicella immunization?

A systematic literature review of the epidemiology and burden of herpes zoster in selected locales in Asia Pacific

Herpes zoster (HZ) is a painful rash which typically affects older adults. This is of concern in Asia-Pacific given its aging population. As HZ epidemiology and burden are evolving, this systematic literature review aimed to update the current understanding of HZ burden and associated costs for selected Asia-Pacific locales. MEDLINE and Embase were searched for English articles of HZ studies conducted in Australia, China, Hong Kong, Japan, Korea, New Zealand, Singapore, and Taiwan. Eligible outcomes included HZ incidence and prevalence, occurrence of HZ-related complications, healthcare resource utilization, costs, and HZ-associated quality of life outcomes. This paper focused on HZ data in the general adult population (N = 90 articles). Substantial HZ-related disease and economic burden were observed in these locales, consistent with global trends. These findings reinforce the increasing burden of HZ and need for preventive strategies, which may include raising awareness and encouraging timely vaccination.

Reduction in Herpes Zoster Antiviral Use Since the Introduction of the Live-Attenuated Zoster Vaccine on Australia's National Immunisation Program: A Population-Based Study from 1994 to 2019

INTRODUCTION

Zostavax, the live-attenuated vaccine used to prevent herpes zoster (HZ), has been available to individuals aged 70 and 71-79 years (phased catch-up) via Australia's National Immunisation Program (NIP) since 2016. There are limited data characterising the incidence of HZ at the level of the Australian population. National prescription data for antivirals used to treat HZ may be used as a proxy for HZ incidence. We aimed to examine trends in antiviral prescriptions supplied for the treatment of HZ in Australia pre- and post-2016, and to assess whether Zostavax's inclusion on the NIP correlated with a reduction in HZ antiviral prescription rates.

METHODS

Using the Australian Pharmaceutical Benefits Scheme and Repatriation Pharmaceutical Benefits Scheme prescribing data, we analysed antiviral prescriptions supplied for the treatment of HZ Australia-wide between 1994 and 2019. Annual prescription rates were calculated, and trends and changes in HZ antiviral use were explored descriptively and using Poisson models.

RESULTS

HZ antiviral prescription rates increased 2.6-fold (160%) between 1995 and 2015 [25.4 (95% CI 25.2, 25.6) and 65.3 (95% CI 64.9, 65.6) prescriptions per 10,000 people, respectively], and then decreased 0.45-fold (55%) between 2016 and 2018 [60.9 (95% CI 60.6, 61.2) and 27.5 (95% CI 27.3, 27.9) prescriptions per 10,000 people, respectively]. The prescription rate for the antiviral famciclovir restricted specifically for treating HZ in immunocompromised individuals increased 8.5-fold (750%) between 2006 (year first listed) and 2019 [0.3 (95% CI 0.3, 0.3) and 2.5 (95% CI 2.4, 2.6) prescriptions per 10,000 people, respectively].

CONCLUSION

The introduction of the live-attenuated HZ vaccine on Australia's formal national vaccination program was associated with a reduction in HZ antiviral prescription rates within the Australian population. The data suggest that the introduction of Shingrix, the non-live subunit zoster vaccine, may also be associated with a similar reduction in HZ antiviral prescriptions used to treat the immunocompromised, as well as the general population, given its accepted greater efficacy over Zostavax.

Early impact of the Australian national shingles vaccination program with the herpes zoster live attenuated vaccine

Herpes zoster (shingles) is a painful condition resulting from reactivation of latent varicella zoster virus (VZV). The Australian National Shingles Vaccination Program (commenced November 2016) provides free herpes zoster vaccination for eligible adults aged 70 years, with a 5-year catch-up program (until October 2021) for adults aged 71-79 years. Patterns and impact of the program were evaluated by analysis of vaccine distribution and delivery data and specific antiviral prescription data from the Pharmaceutical Benefits Scheme. During the first 2 years, uptake of funded live attenuated shingles vaccine ZOSTAVAX® (Zoster Virus Vaccine Live; ZVL) was high across the ongoing and catch-up programs. Before program implementation (2006-2016), herpes zoster coded antiviral prescription rates increased by 2.2% per year (95% CI: 1.5, 2.9) in the 70-79 years age group. In the two years since program launch, herpes zoster antiviral prescription rates declined substantially in this age group, by an average of 13.6% per year (95% CI: 1.5, 24.2). These results indicate that the National Shingles Vaccination Program has been highly successful in vaccinating a considerable proportion of Australian adults aged 70-79 years against herpes zoster and suggest that vaccine uptake was associated with decreased incidence of herpes zoster.

Seasonality of herpes zoster and herpes zoster ophthalmicus

BACKGROUND

Herpes zoster (HZ) and herpes zoster ophthalmicus (HZO) are common and debilitating diseases. There is no consensus in the literature whether HZ and HZO exhibit seasonal patterns.

OBJECTIVES

To determine whether HZ and HZO are seasonal.

STUDY DESIGN

All patients in the OptumLabs® Data Warehouse (OLDW), a longitudinal, insurance claims database with de-identified lives between January 1, 2006 and December 31, 2017 with 365 days or more of continuous enrollment were considered in the study. The database was queried for patients reporting a new ICD-9/ICD-10 code for HZ or HZO and monthly counts of each administrative code were modeled using Morelet wavelets and analyzed for annual periodicity using Fisher's g test.

RESULTS

There were a total of 513,911 new cases of HZ during this time period; 40,166 cases (7.8 %) were reported as HZO. Administrative coding for new cases of HZ exhibited annual periodicity (P < .001) with a peak in the summer. No periodicity was evident for HZO.

CONCLUSIONS

These results contribute to a growing body of evidence suggesting that HZ may be seasonal and help characterize the epidemiology of this common, painful disease.

Monitoring Interest in Herpes Zoster Vaccination: Analysis of Google Search Data

Background

A new recombinant subunit vaccine for herpes zoster (HZ or shingles) was approved by the United States Food and Drug Administration on October 20, 2017 and is expected to replace the previous live attenuated vaccine. There have been low coverage rates with the live attenuated vaccine (Zostavax), ranging from 12-32% of eligible patients receiving the HZ vaccine.

Objective

This study aimed to provide insight into trends and potential reasons for interest in HZ vaccination.

Methods

Internet search data were queried from the Google Health application programming interface from 2004-2017. Seasonality of normalized search volume was analyzed using wavelets and Fisher’s g test.

Results

The search terms “shingles vaccine,” “zoster vaccine,” and “zostavax” all exhibited significant periodicity in the fall months (P<.001), with sharp increases after recommendations for vaccination by public health-related organizations. Although the terms “shingles blisters,” “shingles itch,” “shingles rash,” “skin rash,” and “shingles medicine” exhibited statistically significant periodicities with a seasonal peak in the summer (P<.001), the terms “shingles contagious,” “shingles pain,” “shingles treatment,” and “shingles symptoms” did not reveal an annual trend.

Conclusions

There may be increased interest in HZ vaccination during the fall and after public health organization recommendations are broadcast. This finding points to the possibility that increased awareness of the vaccine through public health announcements could be evaluated as a potential intervention for increasing vaccine coverage.

Trends in Nationwide Herpes Zoster Emergency Department Utilization From 2006 to 2013

Importance

The effect of vaccination on emergency department (ED) utilization for herpes zoster (HZ) has not been examined to date.

Objective

To determine trends in US ED utilization and costs associated with HZ.

Design, Setting, and Participants

The Nationwide Emergency Department Sample data set was examined for temporal trends in the number of visits and costs for treatment of HZ in EDs in the United States from January 1, 2006, through December 31, 2013. Cases of HZ were identified using validated International Classification of Diseases, Ninth Revision-Clinical Modification diagnosis codes. Patients were stratified by age: less than 20 years (varicella vaccine recommended), 20 to 59 years (no vaccine recommended), and 60 years or older (HZ vaccine recommended). Population-based rates were estimated using sampling weights.

Main Outcomes and Measures

Population-based incidence rates of HZ-related ED visits, charge for ED services, and total charges.

Results

A total of 1 350 957 ED visits for HZ were identified between 2006 and 2013, representing 0.13% of all US ED visits. Of these patients, 563 200 (51.7%) were male; mean (SE) age was 54.0 (0.1) years. Between 2006 and 2013, the percentage of HZ-related ED visits increased from 0.13% to 0.14% (8.3%). This growth was driven by patients aged 20 to 59 years (increase of 22.8% [from 0.12% to 0.14% of ED visits]) while the proportion of ED HZ visits decreased for patients aged less than 20 years and 60 years or older, from 0.03% to 0.02% (-39.6%) and from 0.28% to 0.25% (-10.9%), respectively. For all age groups, there was an increase from 2006 to 2013 in overall adjusted total (from $92.83 to $202.47 million) and mean charges (from $763 to $1262) for HZ-related ED visits.

Conclusions and Relevance

The number of ED visits and total cost associated with HZ increased between 2006 and 2013. Greater use was driven by an increased number of visits by patients aged 20 to 59 years, but populations recommended for vaccination (<20 and ≥60 years) demonstrated decreased ED utilization. Per-visit and total costs increased across all age groups. Vaccination may be associated with a reduction of ED utilization. Further research is required to confirm these results and examine the drivers of increased ED costs.

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.

Looking back to move forward: a twenty-year audit of herpes zoster in Asia-Pacific

Background

Herpes zoster (HZ) is a prevalent viral disease that inflicts substantial morbidity and associated healthcare and socioeconomic burdens. Current treatments are not fully effective, especially among the most vulnerable patients. Although widely recommended, vaccination against HZ is not routine; barriers in Asia-Pacific include long-standing neglect of adult immunisation and sparse local data. To address knowledge gaps, raise awareness, and disseminate best practice, we reviewed recent data and guidelines on HZ from the Asia-Pacific region.

Methods

We searched PubMed, Scopus, and World Health Organization databases for articles about HZ published from 1994 to 2014 by authors from Australia, China, Hong Kong, India, Indonesia, Japan, Korea, Malaysia, New Zealand, the Philippines, Singapore, Taiwan, Thailand, and Vietnam. We selected articles about epidemiology, burden, complications, comorbidities, management, prevention, and recommendations/guidelines. Internet searches retrieved additional HZ immunisation guidelines.

Results

From 4007 retrieved articles, we screened-out 1501 duplicates and excluded 1264 extraneous articles, leaving 1242 unique articles. We found guidelines on adult immunisation from Australia, India, Indonesia, Malaysia, New Zealand, the Philippines, South Korea, and Thailand.

HZ epidemiology in Asia-Pacific is similar to elsewhere; incidence rises with age and peaks at around 70 years – lifetime risk is approximately one-third. Average incidence of 3–10/1000 person-years is rising at around 5% per year. The principal risk factors are immunosenescence and immunosuppression. HZ almost always causes pain, and post-herpetic neuralgia is its most common complication. Half or more of hospitalised HZ patients have post-herpetic neuralgia, secondary infections, or inflammatory sequelae that are occasionally fatal. These disease burdens severely diminish patients’ quality of life and incur heavy healthcare utilisation.

Conclusions

Several countries have abundant data on HZ, but others, especially in South-East Asia, very few. However, Asia-Pacific countries generally lack data on HZ vaccine safety, efficacy and cost-effectiveness. Physicians treating HZ and its complications in Asia-Pacific face familiar challenges but, with a vast aged population, Asia bears a unique and growing burden of disease. Given the strong rationale for prevention, most adult immunisation guidelines include HZ vaccine, yet it remains underused. We urge all stakeholders to give higher priority to adult immunisation in general and HZ in particular.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2198-y) contains supplementary material, which is available to authorized users.

Increasing Incidence of Herpes Zoster Over a 60-year Period From a Population-based Study

BACKGROUND

Temporal increases in the incidence of herpes zoster (HZ) have been reported but studies have examined short study periods, and the cause of the increase remains unknown. We examined the long-term trend of HZ.

METHODS

A population-based cohort study was conducted in Olmsted County, Minnesota, using data from 1945-1960 and 1980-2007. Medical records review of possible cases was performed to confirm incident cases of HZ, the patient's immune status, and prescribing of antivirals for HZ. We examined the relative change in the temporal trend in the incidence rates before and after the introduction of the varicella vaccination program.

RESULTS

Of the 8017 patients with HZ, 58.7% were females and 6.6% were immunocompromised. The age- and sex-adjusted incidence rate of HZ increased from 0.76 per 1000 person-years (PY) (95% confidence interval [CI], .63-.89) in 1945-1949 to 3.15 per 1000 PY (95% CI, 3.04-3.26) in 2000-2007. The rate of increase across the time period was 2.5% per year after adjusting for age and sex (adjusted incidence rate ratio, 1.025 [95% CI, 1.023-1.026]; P < .001). The incidence of HZ significantly increased among all age groups and both sexes. We found no change in the rate of increase before vs after the introduction of the varicella vaccination program.

CONCLUSIONS

The incidence of HZ has increased >4-fold over the last 6 decades. This increase is unlikely to be due to the introduction of varicella vaccination, antiviral therapy, or change in the prevalence of immunocompromised individuals.

Varicella-Zoster Virus in Perth, Western Australia: Seasonality and Reactivation

Background

Identification of the factors affecting reactivation of varicella-zoster virus (VZV) largely remains an open question. Exposure to solar ultra violet (UV) radiation is speculated to facilitate reactivation. Should the role of UV in reactivation be significant, VZV reactivation patterns would generally be expected to be synchronous with seasonal UV profiles in temperate climates.

Methods

We analysed age and gender specific VZV notification time series data from Perth, Western Australia (WA). This city has more daily sunshine hours than any other major Australian city. Using the cosinor and generalized linear models, we tested these data for seasonality and correlation with UV and temperature.

Results

We established significant seasonality of varicella notifications and showed that while herpes-zoster (HZ) was not seasonal it had a more stable seasonal component in males over 60 than in any other subpopulation tested. We also detected significant association between HZ notifications and UV for the entire Perth population as well as for females and males separately. In most cases, temperature proved to be a significant factor as well.

Conclusions

Our findings suggest that UV radiation may be important for VZV reactivation, under the assumption that notification data represent an acceptably accurate qualitative measure of true VZV incidence.

Dissecting the indirect effects caused by vaccines into the basic elements

Vaccination directly protects vaccinated individuals, but it also has the potential for indirectly protecting the unvaccinated in a population (herd protection). Unintended negative consequences such as the re-manifestation of infection, mainly expressed as age shifts, result from vaccination programs as well. We discuss the necessary conditions for achieving optimal herd protection (i.e., high quality vaccine-induced immunity, substantial effect on the force of infection, and appropriate vaccine coverage and distribution), as well as the conditions under which age shifts are likely to occur. We show examples to illustrate these effects. Substantial ambiguity in observing and quantifying these indirect vaccine effects makes accurate evaluation troublesome even though the nature of these outcomes may be critical for accurate assessment of the economic value when decision makers are evaluating a novel vaccine for introduction into a particular region or population group. More investigation is needed to identify and develop successful assessment methodologies for precisely analyzing these outcomes.

Increasing trends of herpes zoster in Australia

Background

Increasing trends in incidence of herpes zoster (HZ) have been reported in Australia and internationally. This may reflect the impact of childhood VZV vaccination programs introduced universally in Australia in late 2005. The objective of this study was to evaluate changes in incidence of HZ and PHN in Australia over time, and associated healthcare resource utilisation.

Methods

Australian data on general practice (GP) encounters for HZ, specific antiviral prescribing data from the pharmaceutical benefits scheme, emergency department presentations from the states of NSW and Victoria and national hospitalisation data for HZ were analysed for time trends using regression models. Two time periods (2000-2006 and 2006-2013) were compared which correspond broadly with the pre- and post- universal VZV vaccination period.

Results

All data sources showed increasing rates of HZ with age and over time. The GP database showed a significant annual increase in encounters for HZ of 2.5 per 100,000 between 1998 and 2013, and the rates of prescriptions for HZ increased by 4.2% per year between 2002 and 2012. In the 60+ population HZ incidence was estimated to increase from 11.9 to 15.4 per 1,000 persons using GP data or from 12.8 to 14.2 per 1,000 persons using prescription data (p<0.05, between the two periods). Hospitalisation data did not show the same increasing trend over time, except for the age group ≥80 years. Most emergency visits for HZ were not admitted, and showed significant increases over time.

Discussion

The burden of HZ in Australia is substantial, and continues to increase over time. This increase is seen both pre- and post-universal VZV vaccination in 2005, and is most prominent in the older population. The substantial burden of HZ, along with ageing of the Australian population and the importance of healthy ageing, warrants consideration of HZ vaccination for the elderly.

Decreased varicella and increased herpes zoster incidence at a sentinel medical deputising service in a setting of increasing varicella vaccine coverage in Victoria, Australia, 1998 to 2012

We performed an ecological study using sentinel consultation data from a medical deputising service to assess the impact of increasing coverage with childhood varicella vaccine on the incidence risk of varicella and zoster in the population served by the deputising service in Victoria, Australia from 1998 to 2012. Following a successful vaccination programme, the incidence of varicella in Australia was modelled to decrease and the incidence of zoster to increase, based on a theoretical decrease in boosting of zoster immunity following a decrease in wild varicella virus circulation due to vaccination. Incidence risks (consultation proportions for varicella and zoster) were directly age-standardised to the Melbourne population in 2000, when varicella vaccine was first available. Age-standardised varicella incidence risk peaked in 2000 and halved by 2012. Age-standardised zoster incidence risk remained constant from 1998 to 2002, but had almost doubled by 2012. The increase in zoster consultations largely reflected increases in people younger than 50 years-old. Although causality cannot be inferred from ecological studies, it is generally agreed that the decrease in varicella incidence is due to increasing varicella vaccine coverage. The possible indirect effect of the vaccine on zoster incidence is less clear and ongoing monitoring of zoster is required.

Prevalence and healthcare utilization of herpes zoster and postherpetic neuralgia in South Korea: disparity among patients with different immune statuses

OBJECTIVES

Despite the clinical and epidemiological importance of herpes zoster (HZ) and postherpetic neuralgia (PHN), their disease and economic burden related to immune status has not been studied in South Korea. Our aim was to calculate the prevalence and rate of healthcare utilization related to HZ and PHN among Korean patients stratified by immune status.

METHODS

This retrospective study used the Health Insurance Review and Assessment Service National Patients Sample (HIRA K-NPS) database, which includes all medical claims from January to December 2009 on a representative sample of the Korean population. HZ and PHN patients aged ≥ 50 years were categorized into three groups by immune status: severely immunocompromised group, moderately compromised group, and non-compromised group. The prevalence, disease-related healthcare utilization, and medical costs were compared across the three groups.

RESULTS

We estimated that there were 312,136 HZ patients and 48,461 PHN patients ≥ 50 years in South Korea. The prevalence of HZ and PHN was 18.54 and 2.88 per 1,000 persons, respectively, and increased with deteriorating immune status. The number of outpatient visits and hospitalization rate among HZ patients were highest in the severely immunocompromised group (4.38% and 7.52%, respectively) and lowest in the non-compromised group (3.82% and 4.08%, respectively). The average medical cost per patient in the severe group was the highest (240 US dollars) and that of the non-compromised group was the lowest (161 US dollars). No parameters were significantly different among patients with PHN by immunity.

CONCLUSIONS

HZ patients with severe immunodeficiency had a higher prevalence of HZ, more outpatient visits and hospitalizations, longer hospitalizations, and higher medical costs than their counterparts did. Efforts should be made to reduce the HZ-related burden of severely immunocompromised patients.

Successes and challenges in varicella vaccine

Varicella is a highly contagious disease caused by primary infection with varicella zoster virus (VZV). VZV infection, as well as varicella vaccination, induces VZV-specific antibody and T-cell-mediated immunity, essential for recovery. The immune responses developed contribute to protection following re-exposure to VZV. When cell-mediated immunity declines, as occurs with aging or immunosuppression, reactivation of VZV leads to herpes zoster (HZ). It has been almost 20 years since universal varicella vaccination has been implemented in many areas around the globe and this has resulted in a significant reduction of varicella-associated disease burden. Successes are reviewed here, whilst emphasis is put on the challenges ahead. Most countries that have not implemented routine childhood varicella vaccination have chosen to vaccinate high-risk groups alone. The main reasons for not introducing universal vaccination are discussed, including fear of age shift of peak incidence age and of HZ incidence increase. Possible reasons for not observing the predicted increase in HZ incidence are explored. The advantages and disadvantages of universal vs targeted vaccination as well as different vaccination schedules are discussed.

Varicella and herpes zoster hospitalizations before and after implementation of one-dose varicella vaccination in Australia: an ecological study

OBJECTIVE

To examine trends in varicella and herpes zoster (HZ) hospitalization following the availability and subsequent National Immunization Programme funding of one-dose varicella vaccination in Australia.

METHODS

Varicella vaccination coverage for children born between 2001 and 2009 was obtained from the Australian Childhood Immunization Register. Principal or any coded varicella or HZ hospitalizations were retrieved from the national hospital morbidity database from 1998 to 2010. Trends in hospitalization rates in different age groups and indigenous status were assessed. Incidence rate ratios (IRR) were calculated between periods before and after implementation of immunization programme funding.

FINDINGS

In the first year of the funded immunization programme, varicella vaccine coverage reached 75% in children aged 24 months and more than 80% in children aged 60 months. Compared with the pre-vaccine period, varicella hospitalization rates during the funded programme were significantly lower for age groups younger than 40 years; with the greatest reduction in children aged 18-59 months (IRR: 0.25; 95% confidence interval, CI: 0.22-0.29). Indigenous children had a higher varicella hospitalization rate compared with non-indigenous children before vaccine implementation (IRR: 1.9; 95% CI: 1.4-2.7), but afterwards reached equivalence (IRR: 1.1; 95% CI: 0.7-1.6). The age-standardized HZ hospitalization rate declined between the periods (IRR: 0.95; 95% CI: 0.92-0.97).

CONCLUSION

Rapid attainment of high coverage reduced varicella hospitalizations in the targeted age group, particularly for indigenous children, but also in non-targeted age groups, with no increase in HZ hospitalizations. This suggests high one-dose varicella vaccine coverage can have a substantial impact on severe disease.

Systematic review of incidence and complications of herpes zoster: towards a global perspective

OBJECTIVE

The objective of this study was to characterise the incidence rates of herpes zoster (HZ), also known as shingles, and risk of complications across the world.

DESIGN

We systematically reviewed studies examining the incidence rates of HZ, temporal trends of HZ, the risk of complications including postherpetic neuralgia (PHN) and HZ-associated hospitalisation and mortality rates in the general population. The literature search was conducted using PubMed, EMBASE and the WHO library up to December 2013.

RESULTS

We included 130 studies conducted in 26 countries. The incidence rate of HZ ranged between 3 and 5/1000 person-years in North America, Europe and Asia-Pacific, based on studies using prospective surveillance, electronic medical record data or administrative data with medical record review. A temporal increase in the incidence of HZ was reported in the past several decades across seven countries, often occurring before the introduction of varicella vaccination programmes. The risk of developing PHN varied from 5% to more than 30%, depending on the type of study design, age distribution of study populations and definition. More than 30% of patients with PHN experienced persistent pain for more than 1 year. The risk of recurrence of HZ ranged from 1% to 6%, with long-term follow-up studies showing higher risk (5-6%). Hospitalisation rates ranged from 2 to 25/100 000 person-years, with higher rates among elderly populations.

CONCLUSIONS

HZ is a significant global health burden that is expected to increase as the population ages. Future research with rigorous methods is important.

Influence of frequent infectious exposures on general and varicella-zoster virus-specific immune responses in pediatricians

Reexposure to viruses is assumed to strengthen humoral and cellular immunity via the secondary immune response. We studied the effects of frequent exposure to viral infectious challenges on immunity. Furthermore, we assessed whether repetitive exposures to varicella-zoster virus (VZV) elicited persistently high immune responses. Blood samples from 11 pediatricians and matched controls were assessed at 3 time points and 1 time point, respectively. Besides the assessment of general immunity by means of measuring T-cell subset percentages, antibody titers and gamma interferon (IFN-γ)/interleukin 2 (IL-2)-producing T-cell percentages against adenovirus type 5 (AdV-5), cytomegalovirus (CMV), tetanus toxin (TT), and VZV were determined. Pediatricians had lower levels of circulating CD4(+)-naive T cells and showed boosting of CD8(+) effector memory T cells. Although no effect on humoral immunity was seen, repetitive exposures to VZV induced persistently higher percentages of IFN-γ-positive T cells against all VZV antigens tested (VZV glycoprotein E [gE], VZV intermediate-early protein 62 [IE62], and VZV IE63) than in controls. T cells directed against latency-associated VZV IE63 benefitted the most from natural exogenous boosting. Although no differences in cellular or humoral immunity were found between the pediatricians and controls for AdV-5 or TT, we did find larger immune responses against CMV antigens in pediatricians. Despite the high infectious burden, we detected a robust and diverse immune system in pediatricians. Repetitive exposures to VZV have been shown to induce a stable increased level of VZV-specific cellular but not humoral immunity. Based on our observations, VZV IE63 can be considered a candidate for a zoster vaccine.

Varicella vaccination alters the chronological trends of herpes zoster and varicella

Background

Population studies on trends of varicella and herpes zoster (HZ) associated with varicella zoster vaccination and climate is limited.

Methods

This study used insurance claims data to investigate the chronological changes in incident varicella and HZ associated with varicella zoster vaccination. Poisson regression was used to estimate the occurrence of varicella associated with the occurrence of HZ and vice versa by year, season, sex, temperature, and sunny hours.

Results

The varicella incidence declined from 7.14 to 0.76 per 1,000 person-years in 2000–2009, whereas the HZ incidence increased from 4.04 to 6.24 per 1,000 person-years. Females tended to have a higher risk than men for HZ (p<0.0001) but not varicella. The monthly mean varicella incidence was the lowest in September (160 cases) and the highest in January (425 cases), while the mean HZ incidence was lower in February (370 cases) and higher in August (470 cases). HZ was negatively associated with the incidence of varicella before and after the varicella zoster vaccination (p<0.001), increased 1.6% within one week post-vaccination. The effect of temperature on HZ was attenuated by 18.5% (p<0.0001) in association with vaccination. The varicella risk was positively associated with sun exposure hours, but negatively associated with temperature only before vaccination.

Conclusions

The varicella vaccination is effective in varicella prevention, but the incidence of HZ increases after vaccination. HZ has a stronger association with temperature and UV than with seasonality while varicella risk associated with temperature and UV is diminished.

Herpes Zoster Risk Reduction through Exposure to Chickenpox Patients: A Systematic Multidisciplinary Review

Varicella-zoster virus (VZV) causes chickenpox and may subsequently reactivate to cause herpes zoster later in life. The exogenous boosting hypothesis states that re-exposure to circulating VZV can inhibit VZV reactivation and consequently also herpes zoster in VZV-immune individuals. Using this hypothesis, mathematical models predicted widespread chickenpox vaccination to increase herpes zoster incidence over more than 30 years. Some countries have postponed universal chickenpox vaccination, at least partially based on this prediction. After a systematic search and selection procedure, we analyzed different types of exogenous boosting studies. We graded 13 observational studies on herpes zoster incidence after widespread chickenpox vaccination, 4 longitudinal studies on VZV immunity after re-exposure, 9 epidemiological risk factor studies, 7 mathematical modeling studies as well as 7 other studies. We conclude that exogenous boosting exists, although not for all persons, nor in all situations. Its magnitude is yet to be determined adequately in any study field.

Review of the United States universal varicella vaccination program: Herpes zoster incidence rates, cost-effectiveness, and vaccine efficacy based primarily on the Antelope Valley Varicella Active Surveillance Project data

In a cooperative agreement starting January 1995, prior to the FDA's licensure of the varicella vaccine on March 17, the Centers for Disease Control and Prevention (CDC) funded the Los Angeles Department of Health Services' Antelope Valley Varicella Active Surveillance Project (AV-VASP). Since only varicella case reports were gathered, baseline incidence data for herpes zoster (HZ) or shingles was lacking. Varicella case reports decreased 72%, from 2834 in 1995 to 836 in 2000 at which time approximately 50% of children under 10 years of age had been vaccinated. Starting in 2000, HZ surveillance was added to the project. By 2002, notable increases in HZ incidence rates were reported among both children and adults with a prior history of natural varicella. However, CDC authorities still claimed that no increase in HZ had occurred in any US surveillance site. The basic assumptions inherent to the varicella cost-benefit analysis ignored the significance of exogenous boosting caused by those shedding wild-type VZV. Also ignored was the morbidity associated with even rare serious events following varicella vaccination as well as the morbidity from increasing cases of HZ among adults. Vaccine efficacy declined below 80% in 2001. By 2006, because 20% of vaccinees were experiencing breakthrough varicella and vaccine-induced protection was waning, the CDC recommended a booster dose for children and, in 2007, a shingles vaccination was approved for adults aged 60 years and older. In the prelicensure era, 95% of adults experienced natural chickenpox (usually as children)-these cases were usually benign and resulted in long-term immunity. Varicella vaccination is less effective than the natural immunity that existed in prevaccine communities. Universal varicella vaccination has not proven to be cost-effective as increased HZ morbidity has disproportionately offset cost savings associated with reductions in varicella disease. Universal varicella vaccination has failed to provide long-term protection from VZV disease.

Childhood varicella-zoster virus vaccination in Belgium: cost-effective only in the long run or without exogenous boosting?

AIM

To assess the effectiveness and cost-effectiveness of a universal childhood varicella-zoster vaccination programme in Belgium (1) using the most recent Belgian data on varicella-zoster burden, (2) exploring different options for the timing of the second dose, (3) obtaining results with and without exogenous natural boosting, and (4) investigating the possible additional benefit of zoster booster vaccination for adults at age 50 or 60 y.

METHODS

An extensively studied and improved dynamic model is used to estimate primary and breakthrough chickenpox and zoster cases over time. For a range of vaccination options, we compared the direct costs (health care payer perspective) and health outcomes (including Quality-Adjusted Life-Years (QALYs) lost) associated with chickenpox and herpes zoster. Estimates of social contact patterns, health care use, costs and QALY losses are almost exclusively based on Belgian databases and surveys.

RESULTS AND CONCLUSIONS

If exogenous natural boosting exists, a net loss in QALYs is expected for several decades after implementing a universal chickenpox vaccination programme, due to an increase in zoster mainly in persons aged 50-80 y. This result holds also for scenarios that minimise or counteract the expected increase in zoster incidence (e.g. additional booster vaccinations in adults). However, if the boosting hypothesis is not true or if costs and QALYs are cumulated over at least 33 to more than 100 y after vaccination (depending on the assumptions made), different options for universal 2-dose vaccination against chickenpox in Belgium would be cost-effective at a vaccine price of €43/dose or lower.

The incidence of varicella and herpes zoster in Taiwan during a period of increasing varicella vaccine coverage, 2000-2008

The introduction and the widespread use of the varicella vaccine in Taiwan has led to a 75-80% decrease in the incidence of varicella in children. However the vaccine's long-term impact on the incidence of herpes zoster (HZ) has attracted attention. By controlling gender, underlying diseases, and age effects, a Poisson regression was applied on the 2000-2008 chart records of 240 000 randomly selected residents who enrolled in the Universal National Health Insurance. The results show that, as the vaccine coverage in children increases, the incidence of varicella decreases. However, the incidence of HZ increased even before the implementation of the free varicella vaccination programme in 2004, particularly in females. The increase in the incidence of HZ cannot be entirely and directly attributed to the widespread vaccination of children. Continuous monitoring is needed to understand the secular trends in HZ before and after varicella vaccination in Taiwan and in other countries.