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

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.

Public health impact of herpes zoster vaccination on older adults in Hong Kong

The growing burden of herpes zoster (HZ) in Hong Kong, due to an aging population with increasing life expectancy, may be reduced by vaccination. This study aimed to estimate public health impact of HZ vaccination in Hong Kong. The ZOster ecoNomic Analysis (ZONA) model was adapted with Hong Kong-specific key model inputs/assumptions, where available. Base case analysis involved adults ≥50 years of age (YOA), exploring three vaccination strategies (no vaccination/recombinant zoster vaccine [RZV]/zoster vaccine live [ZVL]) under private market (5% coverage) and mass vaccination (40% coverage) settings. Scenario and sensitivity analyses were performed. In the base case population (3.13 million), without vaccination, 891,024 HZ (28.4%), 156,097 post-herpetic neuralgia (PHN) (5.0%), and 38,755 (1.2%) HZ ophthalmicus (HZO) were projected over their remaining lifetime. Mass RZV vaccination reduced HZ, PHN, and HZO cases by 204,875 (-23.0%), 31,949 (-20.5%), and 8,471 (-21.9%), respectively, which was 4-5 times that reduced with ZVL. RZV was more efficient than ZVL, with lower number needed to vaccinate to prevent one HZ/PHN/HZO case (RZV: 7/40/148; ZVL: 27/163/709). Among all age cohorts, the greatest reduction in cases was projected for RZV (versus no vaccination/ZVL) in the youngest cohort, 50-59 YOA. Results were robust under scenario and sensitivity analyses. HZ burden in Hong Kong is substantial. Mass RZV vaccination is expected to considerably reduce public health burden of HZ among individuals ≥50 YOA, compared with no vaccination/ZVL. Results may support value assessment and decision-making regarding vaccination strategies for HZ prevention in Hong Kong.

Exposure-response relationship between temperature, relative humidity, and varicella: a multicity study in South China

Varicella is a rising public health issue. Several studies have tried to quantify the relationships between meteorological factors and varicella incidence but with inconsistent results. We aim to investigate the impact of temperature and relative humidity on varicella, and to further explore the effect modification of these relationships. In this study, the data of varicella and meteorological factors from 2011 to 2019 in 21 cities of Guangdong Province, China were collected. Distributed lag nonlinear models (DLNM) were constructed to explore the relationship between meteorological factors (temperature and relative humidity) and varicella in each city, controlling in school terms, holidays, seasonality, long-term trends, and day of week. Multivariate meta-analysis was applied to pool the city-specific estimations. And the meta-regression was used to explore the effect modification for the spatial heterogeneity of city-specific meteorological factors and social factors (such as disposable income per capita, vaccination coverage, and so on) on varicella. The results indicated that the relationship between temperature and varicella in 21 cities appeared nonlinear with an inverted S-shaped. The relative risk peaked at 20.8 ℃ (RR = 1.42, 95% CI: 1.22, 1.65). The relative humidity-varicella relationship was approximately L-shaped, with a peaking risk at 69.5% relative humidity (RR = 1.25, 95% CI: 1.04, 1.50). The spatial heterogeneity of temperature-varicella relationships may be caused by income or varicella vaccination coverage. And varicella vaccination coverage may contribute to the spatial heterogeneity of the relative humidity-varicella relationship. The findings can help us deepen the understanding of the meteorological factors-varicella association and provide evidence for developing prevention strategy for varicella epidemic.

Global varicella vaccination programs

Varicella (chickenpox) is an infectious disease caused by the highly contagious varicella zoster virus with a secondary attack rate greater than 90%. From this perspective, we aimed to establish the basis for a national varicella vaccine policy by reviewing vaccination programs and policies of countries that have introduced universal varicella vaccinations. As a result of the spread of varicella, an increasing number of countries are providing 2-dose vaccinations and universally expanding their use. In practice, the efficacy and effectiveness of vaccination differ among vaccines and vaccination programs. Optimized vaccination strategies based on each country's local epidemiology and health resources are required. Accordingly, it is necessary to evaluate the effectiveness of varicella vaccines in different settings. Given the short-term and fragmented vaccine effectiveness evaluation in Korea, it is necessary to evaluate its effectiveness at the national level and determine its schedule based on the evidence generated through these studies.

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.

Varicella Admissions in Children and Adolescents in Portugal: 2000-2015

OBJECTIVES

Varicella is a common, usually benign, and autolimited disease in children but can lead to severe complications and hospitalization. With this study, we aim to analyze all varicella hospitalizations to provide epidemiological information to help outline preventive policies.

METHODS

We assessed all varicella hospitalizations in children aged 0 to 17 years, from 2000 to 2015, in mainland, public Portuguese hospitals using a Portuguese administrative database. Seasonality, geographic distribution, severity, complications, risk factors, use of diagnostic and treatment procedures and hospitalization costs were analyzed.

RESULTS

A total of 5120 hospitalizations were registered, with an annual rate of 17.3 hospitalizations per 100 000 inhabitants. A higher number of hospitalizations occurred during the summer period and in Southern regions. The median length of stay was of 4 days (interquartile range: 3.0-7.0). We found a high rate of severe complications, mostly dermatologic (19.6%), neurologic (6.0%), and respiratory (5.1%). Of the total number of patients, 0.8% were immunocompromised and 0.1% were pregnant. Total direct hospitalization costs during the 16-year period were estimated to be 7 110 719€ (8 603 970 USD), with a mean annual cost of 444 419.92€ (537 748.10 USD).

CONCULSIONS

This is the first national study in which useful epidemiological data to evaluate the burden and impact of varicella in Portugal is provided.

Impact of seasonal influenza on polyclinic attendances for upper respiratory tract infections in Singapore

Purpose

The burden of influenza on primary health-care services is not well established in tropical countries, where there are no clearly defined influenza seasons. We aimed to estimate the association between influenza infection activity and polyclinic attendance rates for upper respiratory tract infections (URTIs) in the Singapore population.

Methods

We used generalized additive time series models to estimate the association between the proportion of respiratory tests positive for influenza infection in Singapore reported to the World Health Organization every week, and the population rate of polyclinic attendances in Singapore for physician-diagnosed URTI, which includes influenza-like illness (ILI), for six years from 2012 through 2017. Where data were available, we controlled for other infections that can cause fever or respiratory symptoms.

Results

Influenza, dengue fever and chickenpox (varicella) were positively associated with acute URTI polyclinic attendances. The estimated URTI polyclinic attendance rates attributable to influenza, dengue fever and chickenpox were 618.9 (95% confidence interval [CI]: 501.6–736.3), 153.3 (95% CI: 16.5–290.2) and 1751.5 (95% CI: 1246.3–2256.8) per 100 000 population per year, respectively.

Conclusion

Influenza poses a considerable burden on primary health-care services in Singapore. However, a substantial number of polyclinic attendances due to febrile infections such as dengue fever and chickenpox appear to be recorded as URTI in the polyclinic database. These associations require further investigation.

A systematic literature review to assess the burden of herpes zoster disease in China

INTRODUCTION

Herpes zoster (HZ) or shingles occurs as a result of reactivation after a primary infection with varicella zoster virus (chickenpox). The burden of HZ in older adults in China is not well understood. We conducted a systematic literature review to understand the burden of disease related to HZ, its complications, and associated costs in China.

AREAS COVERED

Using publications retrieved from Chinese and English literature databases, we described incidence and prevalence of HZ, occurrence of HZ-related complications, and costs associated with HZ in mainland China, Taiwan, and Hong Kong.

EXPERT OPINION

The data, although limited, indicate that the burden of disease due to HZ is substantial in China, with incidence rates that are comparable to the rest of the world. Recently, an adjuvanted recombinant HZ vaccine was approved for use in China. Disease prevention is likely to reduce the burden of disease, with potentially significant economic benefits. However, understanding the public health impact of vaccination in China will require extensive baseline information about incidence, complication rates, and associated costs. This review gives an overview of available research, but also reveals existing gaps. Well-designed observational studies are needed to quantify the total burden of disease and potential impact of prevention through vaccination.

Association between climatic factors and varicella incidence in Guangzhou, Southern China, 2006-2018

OBJECTIVE

To analyze the correlation between climatic factors and the incidence of varicella in Guangzhou, and improve the prevention measures about public health.

METHODS

Data for daily climatic variables and varicella incidence from 2006 to 2018 in Guangzhou were collected from the Guangzhou Meteorological Bureau and the National Notifiable Disease Report System. Distributed lag nonlinear models were applied to evaluate the association between climatic factors and varicella incidence.

RESULTS

The nonlinear effects of meteorological factors were observed. At lag day21，when the mean temperature was 31.8 °C, the relative risk was the highest as 1.11 (95% CI: 1.07-1.16). When the diurnal temperature range was 24.0 °C at lag day 20, the highest RR was 1.11 (95% CI: 1.05-1.17). For rainfall, the highest RR was 1.09 (95% CI: 1.01-1.19) at lag day 21，when the aggregate rainfall was 160 mm. When air pressure was 1028 hPa, the highest RR was 1.08 (95% CI: 1.04-1.13) at lag day 21. When wind speed was 0.7 m/s, the highest RR was 1.07 (95% CI: 1.04-1.11) at lag day 7. When the hours of sunshine were 9.0 h at lag day 21, the RR was highest as 1.04 (95% CI: 1.02-1.05). Aggregate rainfall, air pressure, and sunshine hours were positively correlated with the incidence of varicella, which was inconsistent with the wind velocity. Mean temperature showed a reverse U-shape curve relationship with varicella, while the diurnal temperature range showed a binomial distribution curve. The extreme effect of climatic factors on the varicella cases was statistically significant, apart from the extremely low effect of rainfall.

CONCLUSION

Our preliminary results offered fundamental knowledge which might be benefit to give an insight into epidemic trends of varicella and develop an early warning system. We could use our findings about influential factors to strengthen the intervention and prevention of varicella.

Varicella vaccine dose depended effectiveness and waning among preschool children in Hong Kong

In Hong Kong, universal varicella vaccination was introduced in July 2014 with a two-dose schedule but the vaccines had been available in the private market since 1996. With data from varicella notification and surveys on immunization coverage, we used the screening method to estimate dose-specific varicella vaccine effectiveness (VE) among preschool children in Hong Kong before universal vaccination. We estimated the VE of one- and two-dose varicella vaccination against all notified varicella as 69.4% (95% confidence interval (95% CI) 69.5-71.2) and 93.4% (95% CI 91.7-94.7), respectively. We found that VE did not decrease with time since receipt. Varicella vaccine was more effective against complications (85.4% [95% CI 48.8-95.8] for one dose and 100% [95% CI -Inf to 100] for two doses) and against hospital admission (75.2% [95% CI 53.4-86.8] for one dose and 93.1% [95% CI 47.1-99.1] for two doses). Lower protection of one-dose varicella vaccine resulted in breakthrough varicella. Under universal vaccination, second-dose varicella vaccine (given as combined measles, mumps, rubella and varicella vaccine) was first scheduled for children when they reach primary one (about 6 years of age) and was recently advanced to 18 months of age. Shortening the interval between the first dose and second dose of varicella vaccination should reduce breakthrough varicella and outbreaks in preschool.

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.

Seroprevalence and molecular characteristics of varicella-zoster virus infection in Chinese children

Background

Varicella-zoster virus (VZV) infection in children is an important public health problem in China. We performed the current study to explore the seroprevalence of VZV infection in Chinese children in order to provide more information for improvement of varicella vaccination in China.

Methods

Three thousand fourteen children were recruited from Chinese kindergarten students aged from four to six years. Anti-VZV IgG and IgM were assayed using enzyme-linked immunosorbent assay. Both ORF22 and ORF62 of VZV were amplified, sequenced, and analyzed by nested PCR.

Results

Among 3014 children, 43.9% of boys and 46.3% of girls were vaccinated with varicella vaccine, respectively. The seroprevalence of anti-VZV IgG was 54.4% in the children with varicella vaccination, which was significantly higher than those in unvaccinated children (49.2%) (χ² = 8.206, P = 0.004). Among of the vaccinated children, the detection rates of VZV IgG antibody increased with age, with 49.4, 50.9 and 58.9% in 4, 5 and 6-year groups, respectively (Trend χ² = 17.202, P = 0.002). However, there was no difference in anti-VZV IgG detection rates among those unvaccinated children in different age groups (Trend χ² = 8.681, P = 0.070). In addition, 13 boys and 13 girls were positive for anti-VZV IgM, respectively. Among of them, eight children (0.6%) have received varicella vaccination, which was similar to those in unvaccinated children (1.1%). However, only one ORF22 sequence was isolated from an unvaccinated 5-year boy. Compared to the reference VZV sequences, the nucleotide homology was estimated to be 99.7% with genotype J.

Conclusions

Our study indicated that about half of Chinese children aged four to six years have a high risk of VZV infection. It should be helpful for the evaluation on the necessity of varicella immunization in China.

Analysis of sero-epidemiological characteristics of varicella in healthy children in Jiangsu Province, China

Background

In recent years, outbreaks of varicella have continued to occur, and the coverage rate of varicella vaccine in Jiangsu Province, China, remains unclear. This study aims to analyse the levels of immune antibody against varicella and obtain a comprehensive understanding of the varicella attenuated live vaccine (VarV) coverage rate in children aged 1–9 years in Jiangsu Province.

Methods

From June to October 2016, a cross-sectional survey was conducted to collect 3631 serum samples from healthy children aged 1–9 years in Jiangsu Province. The immunoglobulin G (IgG) antibody levels of varicella were detected by enzyme-linked immunosorbent assay (ELISA).

Results

The VarV coverage rate of healthy children was only 43.1% (95% CI: 41.1–44.7%). The seroprevalence after vaccination with a single dose of VarV was only 57.1%, and the overall seropositivity and geometric antibody titre (GMC) were 43.5% and 225.4 mU/ml, respectively. The seropositivity was significantly higher in girls than in boys (χ² = 18.82, P < 0.001). The difference in seropositivity between the 5–9 age group and 1–4 age group was statistically significant (χ² = 84.31, P < 0.001). The difference in seropositivity between different regions was statistically significant, with the highest seropositivity in the northern area, 53.7% (χ² = 35.64, P < 0.001). The seropositivity in the group receiving one dose of VarV was significantly higher than that of the unvaccinated group (χ² = 205.16, P < 0.001). Linear regression analysis suggested that the GMC of varicella antibodies wanes with the time since vaccination (F = 65.01, P = 0.002).

Conclusion

The VarV coverage rate of healthy children in Jiangsu Province was low. Sero-conversion rates were also low after one dose of VarV, and the immune effectiveness of a single dose of VarV was limited. To control the spread of varicella, VarV should be included in the routine immunization program, and strengthened immunization measures for the varicella-susceptible population warrant additional consideration.