Herpes zoster incidence in Germany - an indirect validation study for self-reported disease data from pretest studies of the population-based German National Cohort

The Incidence of Herpes Zoster Complications: A Systematic Literature Review

INTRODUCTION

The objective of this work was to summarize the incidence of herpes zoster (HZ) complications in different populations.

METHODS

Systematic literature review of PubMed, Embase, and Virtual Health Library records between January 1, 2002 and October 20, 2022 using search strings for HZ, complications, and frequency measurements.

RESULTS

The review included 124 studies, most conducted in the general population (n = 93) and on individuals with comorbidities (n = 41) ≥ 18 years of age. Most studies were conducted in Europe (n = 44), Asia (n = 40), and North America (n = 36). Postherpetic neuralgia (PHN) was the most studied neurological complication. Variable relative PHN incidence was found in the general population (2.6-46.7%) or based on diagnosis: immunocompromised (3.9-33.8%), depression (0-50%), and human immunodeficiency virus (HIV) (6.1-40.2%). High incidence rates were observed in hematological malignancies (HM) and solid organ malignancies (132.5 and 93.7 per 1000 person-years, respectively). Ocular complications were frequently reported with herpes zoster ophthalmicus (HZO). The relative incidence (incidence rate) of HZO in the general population was reported as 1.4-15.9% (0.31-0.35 per 1000 person-years). High relative incidence was observed in HIV (up to 10.1%) and HM (3.2-11.3%). Disseminated HZ was the most frequently reported cutaneous complication. The relative incidence of disseminated HZ was 0.3-8.2% in the general population, 0-0.5% in the immunocompetent, and 0-20.6% in patients with comorbidities. High relative incidence was reported in HM and solid organ transplant (up to 19.3% and 14.8%, respectively).

DISCUSSION

Most reported complications were neurological (n = 110), ocular (n = 48), and cutaneous (n = 38). Few studies stratified complications by age or gender (or both). Incidence appeared higher in select immunocompromised populations. Higher incidence was associated with older age in several studies; the general association with gender was unclear.

CONCLUSIONS

Variable incidence of HZ complications was reported by population subgroup. Further research is required to quantitatively analyze incidence by age, gender, and location.

Risk factors for herpes zoster infections: a systematic review and meta-analysis unveiling common trends and heterogeneity patterns

PURPOSE

The burden of herpes zoster (HZ) is substantial and numerous chronic underlying conditions are known as predisposing risk factors for HZ onset. Thus, a comprehensive study is needed to synthesize existing evidence. This study aims to comprehensively identify these risk factors.

METHODS

A systematic literature search was done using MEDLINE via PubMed, EMBASE and Web of Science for studies published from January 1, 2003 to January 1, 2023. A random-effects model was used to estimate pooled Odds Ratios (OR). Heterogeneity was assessed using the I2 statistic. For sensitivity analyses basic outlier removal, leave-one-out validation and Graphic Display of Heterogeneity (GOSH) plots with different algorithms were employed to further analyze heterogeneity patterns. Finally, a multiple meta-regression was conducted.

RESULTS

Of 6392 considered records, 80 were included in the meta-analysis. 21 different conditions were identified as potential risk factors for HZ: asthma, autoimmune disorders, cancer, cardiovascular disorders, chronic heart failure (CHF), chronic obstructive pulmonary disorder (COPD), depression, diabetes, digestive disorders, endocrine and metabolic disorders, hematological disorders, HIV, inflammatory bowel disease (IBD), mental health conditions, musculoskeletal disorders, neurological disorders, psoriasis, renal disorders, rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and transplantation. Transplantation was associated with the highest risk of HZ (OR = 4.51 (95% CI [1.9-10.7])). Other risk factors ranged from OR = 1.17-2.87, indicating an increased risk for all underlying conditions. Heterogeneity was substantial in all provided analyses. Sensitivity analyses showed comparable results regarding the pooled effects and heterogeneity.

CONCLUSIONS

This study showed an increased risk of HZ infections for all identified factors.

Vaccines for preventing herpes zoster in older adults

BACKGROUND

Herpes zoster, commonly known as shingles, is a neurocutaneous disease caused by the reactivation of the virus that causes varicella (chickenpox). After resolution of the varicella episode, the virus can remain latent in the sensitive dorsal ganglia of the spine. Years later, with declining immunity, the varicella zoster virus (VZV) can reactivate and cause herpes zoster, an extremely painful condition that can last many weeks or months and significantly compromise the quality of life of the affected person. The natural process of ageing is associated with a reduction in cellular immunity, and this predisposes older adults to herpes zoster. Vaccination with an attenuated form of the VZV activates specific T-cell production avoiding viral reactivation. Two types of herpes zoster vaccines are currently available. One of them is the single-dose live attenuated zoster vaccine (LZV), which contains the same live attenuated virus used in the chickenpox vaccine, but it has over 14-fold more plaque-forming units of the attenuated virus per dose. The other is the recombinant zoster vaccine (RZV) which does not contain the live attenuated virus, but rather a small fraction of the virus that cannot replicate but can boost immunogenicity. The recommended schedule for the RZV is two doses two months apart. This is an update of a Cochrane Review first published in 2010, and updated in 2012, 2016, and 2019.

OBJECTIVES

To evaluate the effectiveness and safety of vaccination for preventing herpes zoster in older adults.

SEARCH METHODS

For this 2022 update, we searched the Cochrane Central Register of Controlled Trials (CENTRAL 2022, Issue 10), MEDLINE (1948 to October 2022), Embase (2010 to October 2022), CINAHL (1981 to October 2022), LILACS (1982 to October 2022), and three trial registries.

SELECTION CRITERIA

We included studies involving healthy older adults (mean age 60 years or older). We included randomised controlled trials (RCTs) or quasi-RCTs comparing zoster vaccine (any dose and potency) versus any other type of intervention (e.g. varicella vaccine, antiviral medication), placebo, or no intervention (no vaccine). Outcomes were cumulative incidence of herpes zoster, adverse events (death, serious adverse events, systemic reactions, or local reaction occurring at any time after vaccination), and dropouts.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included two new studies involving 1736 participants in this update. The review now includes a total of 26 studies involving 90,259 healthy older adults with a mean age of 63.7 years. Only three studies assessed the cumulative incidence of herpes zoster in groups that received vaccines versus placebo. Most studies were conducted in high-income countries in Europe and North America and included healthy Caucasians (understood to be white participants) aged 60 years or over with no immunosuppressive comorbidities. Two studies were conducted in Japan and one study was conducted in the Republic of Korea. Sixteen studies used LZV. Ten studies tested an RZV. The overall certainty of the evidence was moderate, which indicates that the intervention probably works. Most data for the primary outcome (cumulative incidence of herpes zoster) and secondary outcomes (adverse events and dropouts) came from studies that had a low risk of bias and included a large number of participants. The cumulative incidence of herpes zoster at up to three years of follow-up was lower in participants who received the LZV (one dose subcutaneously) than in those who received placebo (risk ratio (RR) 0.49, 95% confidence interval (CI) 0.43 to 0.56; risk difference (RD) 2%; number needed to treat for an additional beneficial outcome (NNTB) 50; moderate-certainty evidence) in the largest study, which included 38,546 participants. There were no differences between the vaccinated and placebo groups for serious adverse events (RR 1.08, 95% CI 0.95 to 1.21) or deaths (RR 1.01, 95% CI 0.92 to 1.11; moderate-certainty evidence). The vaccinated group had a higher cumulative incidence of one or more adverse events (RR 1.71, 95% CI 1.38 to 2.11; RD 23%; number needed to treat for an additional harmful outcome (NNTH) 4.3) and injection site adverse events (RR 3.73, 95% CI 1.93 to 7.21; RD 28%; NNTH 3.6; moderate-certainty evidence) of mild to moderate intensity. These data came from four studies with 6980 participants aged 60 years or older. Two studies (29,311 participants for safety evaluation and 22,022 participants for efficacy evaluation) compared RZV (two doses intramuscularly, two months apart) versus placebo. Participants who received the new vaccine had a lower cumulative incidence of herpes zoster at 3.2 years follow-up (RR 0.08, 95% CI 0.03 to 0.23; RD 3%; NNTB 33; moderate-certainty evidence), probably indicating a favourable profile of the intervention. There were no differences between the vaccinated and placebo groups in cumulative incidence of serious adverse events (RR 0.97, 95% CI 0.91 to 1.03) or deaths (RR 0.94, 95% CI 0.84 to 1.04; moderate-certainty evidence). The vaccinated group had a higher cumulative incidence of adverse events, any systemic symptom (RR 2.23, 95% CI 2.12 to 2.34; RD 33%; NNTH 3.0), and any local symptom (RR 6.89, 95% CI 6.37 to 7.45; RD 67%; NNTH 1.5). Although most participants reported that their symptoms were of mild to moderate intensity, the risk of dropouts (participants not returning for the second dose, two months after the first dose) was higher in the vaccine group than in the placebo group (RR 1.25, 95% CI 1.13 to 1.39; RD 1%; NNTH 100, moderate-certainty evidence). Only one study reported funding from a non-commercial source (a university research foundation). All other included studies received funding from pharmaceutical companies. We did not conduct subgroup and sensitivity analyses AUTHORS' CONCLUSIONS: LZV (single dose) and RZV (two doses) are probably effective in preventing shingles disease for at least three years. To date, there are no data to recommend revaccination after receiving the basic schedule for each type of vaccine. Both vaccines produce systemic and injection site adverse events of mild to moderate intensity. The conclusions did not change in relation to the previous version of the systematic review.

Prevention of Herpes Zoster: A Focus on the Effectiveness and Safety of Herpes Zoster Vaccines

Infection with varicella zoster virus typically occurs in children and it can cause primary varicella infection or "chickenpox", or it can reactivate later in life and cause herpes zoster or "shingles". Herpes zoster mainly occurs in older adults, causing a reduction in activities of daily living, impacting quality of life, and may lead to serious complications, including chronic pain. Two vaccines are marketed to prevent herpes zoster: the live zoster vaccine and the non-live, recombinant zoster vaccine. The pre-licensure clinical trials show the efficacy of the live zoster vaccine to be between 50 and 70% and for the recombinant vaccine to be higher at 90 to 97%. Real-world effectiveness studies, with a follow-up of approximately 10 years, were reviewed in this article. These data corroborated the efficacy studies, with vaccine effectiveness being 46% and 85% for the live and recombinant vaccines, respectively. Safety data from the effectiveness studies show similar results to the clinical trials with mostly local injection-site reactions and mild systemic reactions seen with both vaccines, although in larger proportions with the recombinant vaccine. Rare adverse events, occurring less than 1% of the time, have been seen with both vaccine types and include disseminated herpes zoster with the live zoster vaccine and Guillain-Barré syndrome with the recombinant vaccine. The wider use of preventative measures with vaccines will reduce the herpes zoster burden of illness seen in older adults.

The Impact of Universal Varicella Vaccination on Herpes Zoster Incidence in the United States: Comparison of Birth Cohorts Preceding and Following Varicella Vaccination Program Launch

When the US varicella vaccination program was introduced in 1995, its impacts on the epidemiology of herpes zoster (HZ) were not precisely known. We used a large claims database to examine HZ incidence in the US during 1998-2019 among persons aged ≥30 years (the prevaccine cohort, born before 1990), and aged 1-29 years (includes the postvaccine cohort, born since 1990). We defined incident HZ as the first instance of an outpatient or emergency department (ED) claim with an HZ diagnostic code. Additionally, we examined the proportion of HZ visits among all ED visits as a complementary method to assess for healthcare-seeking artifacts in the findings. In persons aged ≥30 years (prevaccine cohort), we observed age-specific increases in HZ incidence during the earlier study years, with decelerations in later years, starting in 2007 with oldest age groups. Similar patterns were seen when we examined HZ visits as a proportion of all ED visits. For persons aged 1-29 years, age-specific HZ incidence increased early in the study period for the oldest age groups who were born prevaccine, but later declined in a stepwise pattern once each age group was comprised of persons born in the postvaccine period. Our results, corroborated with previously published studies, do not support prior modeling predictions that the varicella vaccination program would increase HZ incidence among adult cohorts who previously experienced varicella. Our findings also suggest that continued declines in age-specific HZ incidence as varicella-vaccinated cohorts age are likely.

Radiotherapy Increases the Incidence of Herpes Zoster in Oral Cavity Cancer Patients - a National Population-based Cohort Study

BACKGROUND/AIM

Oral cavity cancer is a major health problem worldwide. The herpes zoster vaccine is an effective method to protect against herpes zoster infection. In this study we aimed to determine the relationship between herpes zoster and oral cavity cancer.

PATIENTS AND METHODS

The Longitudinal Generation Tracking Database in Taiwan was used to select oral and non-oral cavity cancer patients. The primary endpoint was herpes zoster.

RESULTS

We included 3131 oral cavity cancer patients and 3131 non-oral cavity cancer patients. Patients with oral cavity cancer [adjusted hazard ratio (HR)=1.66, 95% confidence interval (CI)=1.27-2.16] had a significantly higher risk of herpes zoster compared to the control group. The oral cavity patients who received radiotherapy (adjusted HR=1.79, 95%CI=1.12-2.86) had a significantly higher risk of herpes zoster compared to the oral cavity patients who did not receive radiotherapy.

CONCLUSION

Radiotherapy increases the incidence of herpes zoster infection in oral cavity cancer patients.

Burden of Herpes Zoster in Adult Patients with Underlying Conditions: Analysis of German Claims Data, 2007-2018

INTRODUCTION

Several chronic underlying conditions (UCs) are known to be risk factors for developing herpes zoster (HZ) and to increase the severity of HZ and its risk of recurrence. The aim of this study was to investigate the incidence and recurrence of HZ in adult patients with one or multiple UCs.

METHODS

A retrospective cohort study based on claims data representing 13% of the statutory health insurance population from 2007 to 2018 in Germany was performed. Patients aged ≥ 18 years were included when at least one of the following UCs was diagnosed: asthma, chronic heart failure, chronic obstructive pulmonary disease (COPD), coronary heart disease (CHD), depression, diabetes mellitus type 1 or 2, and rheumatoid arthritis (RA). Exact matching was used to account for differences in the distribution of age and sex between the case and matched control cohorts. Multi-morbidity was considered in sensitivity analyses by analyzing patients with only one UC.

RESULTS

Patients with asthma, CHD, COPD, depression, and RA had, on average, a 30% increased risk of developing acute HZ compared to patients without any UC. RA was found to have the highest odds ratio among these conditions, varying from 1.37 to 1.57 for all age groups. Patients with depression also showed a high risk of developing HZ. Analysis of recurrence indicated that patients with at least one UC in the age groups 18-49 years and 50-59 years had the highest risk for a recurrent HZ. After experiencing a first recurrence, patients, regardless of age group, had a two- to threefold higher risk for a second recurrence.

CONCLUSION

This study of representative claims data shows a higher HZ incidence and recurrence frequency in patients with UCs. These results provide relevant information for national health care guidelines and disease management programs.

Association between lateral epicondylitis and the risk of herpes zoster development

BACKGROUND

Diseases burden is associated with herpes zoster (HZ) development. However, the relationship between lateral epicondylitis (LE) and HZ remains unknown.

AIM

This study investigated the association between LE and the risk of HZ development.

METHODS

In this study, we collected data from the National Health Insurance Research Database of Taiwan. Patients who were diagnosed as having LE for the first time between 2000 and 2012 were included in the LE cohort. Patients without LE were randomly selected from the same database for inclusion in the control cohort. The outcome of interest was the first diagnosis of HZ during the follow-up period.

RESULTS

The overall incidence rates of HZ in the LE and control cohort were 8.95 and 7.14 per 1,000 person-years, respectively. After adjustments were made, the LE cohort had a higher hazard ratio of HZ than the control cohort [adjusted hazard ratio (aHR) = 1.23]. The risk of HZ was significantly higher in those aged 50 to 64 years (aHR = 2.05) and in those over the age of 65 years (aHR = 2.50), compared with those aged ≤49 years. The risk of HZ was significantly higher in women (aHR = 1.17). The female patients with LE had a higher risk of HZ development than controls (aHR = 1.27).

CONCLUSION

Women with LE had a higher risk of HZ development. HZ vaccination may be needed for the female patients with LE.

Gender-specific hearing loss in German adults aged 18 to 84 years compared to US-American and current European studies

INTRODUCTION

From an epidemiological point of view, the increase of pure-tone hearing thresholds as one aspect of biological ageing is moderated by societal factors. Since health policies refer to empirical findings, it is reasonable to replicate population-based hearing surveys and to compare estimates for different birth cohorts from the same regions or, conversely, for the same birth cohorts from different regions.

METHODS

We pooled data from two independent cross-sectional German studies conducted between 2008 and 2012 and including 3105 adults. The increase of thresholds, the prevalence and risk of hearing impairment (HI) by age and gender were compared to results reported for European and US-American studies that were carried out at about the same time. Since these studies differed with regard to the age limits, the statistical approaches and, importantly, their definitions of HI, data adjustments were performed to enable the comparison.

RESULTS

Overall, 15.5% of the participants in the German studies showed a pure-tone average at 0.5, 1, 2, and 4 kHz in the better ear (PTA) greater than 25 dB HL and 8.6% had a PTA of at least 35 dB HL. Based on one-to-one comparisons, the German estimates demonstrated a good agreement to a large Dutch study and with some reservations to a Swedish study, but considerable differences to US-American results. Comprehensive comparisons of the within-study gender differences showed that age-related HI was less and the gender gap was markedly smaller in Europe compared to the US due to the lower HI in males found in the European studies.

CONCLUSION

Discrepancies in measurement procedures, conditions, and equipment that complicate the comparison of absolute HI estimates across studies play no or only a marginal role when comparing relative estimates. Hence, the gender gap differences reviewed in this analysis possibly stem from societal conditions that distinguish societies commonly labeled modern industrialized western countries.

[Self-reported infections in the German National Cohort (GNC) in the context of the current research landscape]

BACKGROUND

Infectious diseases continue to play an important role for disease perception, health-economic considerations and public health in Germany. In recent years, infectious diseases have been linked to the development of non-communicable diseases. Analyses of the German National Cohort (GNC) may provide deeper insights into this issue and pave the way for new targeted approaches in disease prevention.

OBJECTIVES

The aim was to describe the tools used to assess infectious diseases and to present initial data on infectious disease frequencies, as well as to relate the GNC assessment tools to data collection methods in other studies in Germany.

METHODS

As part of the baseline examination, questions regarding infectious diseases were administered using both an interview and a self-administered touchscreen questionnaire. Data from the initial 101,787 GNC participants were analysed.

RESULTS

In the interview, 0.2% (HIV/AIDS) to 8.6% (shingles) of respondents reported ever having a medical diagnosis of shingles, postherpetic neuralgia (in cases where shingles was reported), hepatitis B/C, HIV/AIDS, tuberculosis or sepsis if treated in hospital. In the questionnaire, 12% (cystitis) to 81% (upper respiratory tract infections) of respondents reported having experienced at least one occurrence of upper or lower respiratory tract infections, gastrointestinal infections, cystitis or fever within the past 12 months.

OUTLOOK

The cross-sectional analyses of data and tools presented here - for example on determinants of susceptibility to self-reported infections - can be anticipated from the year 2021 onward. Beyond that, more extensive research into infectious disease epidemiology will follow, particularly once analyses of GNC biological materials have been performed.

Vaccines for preventing herpes zoster in older adults

BACKGROUND

Herpes zoster, commonly known as shingles, is a neurocutaneous disease caused by the reactivation of the virus that causes varicella (chickenpox). After resolution of the varicella episode, the virus can remain latent in the sensitive dorsal ganglia of the spine. Years later, with declining immunity, the varicella zoster virus (VZV) can reactivate and cause herpes zoster, an extremely painful condition that can last many weeks or months and significantly compromise the quality of life of the affected person. The natural process of aging is associated with a reduction in cellular immunity, and this predisposes older people to herpes zoster. Vaccination with an attenuated form of the VZV activates specific T-cell production avoiding viral reactivation. The USA Food and Drug Administration has approved a herpes zoster vaccine with an attenuated active virus, live zoster vaccine (LZV), for clinical use amongst older adults, which has been tested in large populations. A new adjuvanted recombinant VZV subunit zoster vaccine, recombinant zoster vaccine (RZV), has also been approved. It consists of recombinant VZV glycoprotein E and a liposome-based AS01B adjuvant system. This is an update of a Cochrane Review last updated in 2016.

OBJECTIVES

To evaluate the effectiveness and safety of vaccination for preventing herpes zoster in older adults.

SEARCH METHODS

For this 2019 update, we searched the Cochrane Central Register of Controlled Trials (CENTRAL, Issue 1, January 2019), MEDLINE (1948 to January 2019), Embase (2010 to January 2019), CINAHL (1981 to January 2019), LILACS (1982 to January 2019), WHO ICTRP (on 31 January 2019) and ClinicalTrials.gov (on 31 January 2019).

SELECTION CRITERIA

We included randomised controlled trials (RCTs) or quasi-RCTs comparing zoster vaccine (any dose and potency) versus any other type of intervention (e.g. varicella vaccine, antiviral medication), placebo, or no intervention (no vaccine). Outcomes were incidence of herpes zoster, adverse events (death, serious adverse events, systemic reactions, or local reaction occurring at any time after vaccination), and dropouts.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included 11 new studies involving 18,615 participants in this update. The review now includes a total of 24 studies involving 88,531 participants. Only three studies assessed the incidence of herpes zoster in groups that received vaccines versus placebo. Most studies were conducted in high-income countries in Europe and North America and included healthy Caucasians (understood to be white participants) aged 60 years or over with no immunosuppressive comorbidities. Two studies were conducted in Japan. Fifteen studies used LZV. Nine studies tested an RZV. The overall quality of the evidence was moderate. Most data for the primary outcome (incidence of herpes zoster) and secondary outcomes (adverse events and dropouts) came from studies that had a low risk of bias and included a large number of participants. The incidence of herpes zoster at up to three years follow-up was lower in participants who received the LZV (one dose subcutaneously) than in those who received placebo (risk ratio (RR) 0.49, 95% confidence interval (CI) 0.43 to 0.56; risk difference (RD) 2%; number needed to treat for an additional beneficial outcome (NNTB) 50; moderate-quality evidence) in the largest study, which included 38,546 participants. There were no differences between the vaccinated and placebo groups for serious adverse events (RR 1.08, 95% CI 0.95 to 1.21) or deaths (RR 1.01, 95% CI 0.92 to 1.11; moderate-quality evidence). The vaccinated group had a higher incidence of one or more adverse events (RR 1.71, 95% CI 1.38 to 2.11; RD 23%; number needed to treat for an additional harmful outcome (NNTH) 4.3) and injection site adverse events (RR 3.73, 95% CI 1.93 to 7.21; RD 28%; NNTH 3.6) of mild to moderate intensity (moderate-quality evidence). These data came from four studies with 6980 participants aged 60 years or over. Two studies (29,311 participants for safety evaluation and 22,022 participants for efficacy evaluation) compared RZV (two doses intramuscularly, two months apart) versus placebo. Participants who received the new vaccine had a lower incidence of herpes zoster at 3.2 years follow-up (RR 0.08, 95% CI 0.03 to 0.23; RD 3%; NNTB 33; moderate-quality evidence). There were no differences between the vaccinated and placebo groups in incidence of serious adverse events (RR 0.97, 95% CI 0.91 to 1.03) or deaths (RR 0.94, 95% CI 0.84 to 1.04; moderate-quality evidence). The vaccinated group had a higher incidence of adverse events, any systemic symptom (RR 2.23, 95% CI 2.12 to 2.34; RD 33%; NNTH 3.0), and any local symptom (RR 6.89, 95% CI 6.37 to 7.45; RD 67%; NNTH 1.5). Although most participants reported that there symptoms were of mild to moderate intensity, the risk of dropouts (participants not returning for the second dose, two months after the first dose) was higher in the vaccine group than in the placebo group (RR 1.25, 95% CI 1.13 to 1.39; RD 1%; NNTH 100, moderate-quality evidence). Only one study reported funding from a non-commercial source (a university research foundation). All of the other included studies received funding from pharmaceutical companies. We did not conduct subgroup and sensitivity analyses AUTHORS' CONCLUSIONS: LZV and RZV are effective in preventing herpes zoster disease for up to three years (the main studies did not follow participants for more than three years). To date, there are no data to recommend revaccination after receiving the basic schedule for each type of vaccine. Both vaccines produce systemic and injection site adverse events of mild to moderate intensity.

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.