Global Varicella Vaccine Effectiveness: A Meta-analysis

Expanded spectrum of varicella disease and the need for vaccination in India

Varicella vaccine was first licensed in Japan and South Korea in 1989 for use in healthy children and was introduced in US in 1995. So far, 29 countries have adopted varicella vaccine in their universal immunization program (UIP). No Asian country, India included, has adopted the varicella vaccine as part of their UIP. The extra-cutaneous sites for VZV diseases are central nervous system and gastrointestinal tract, the expanded disease spectrum includes vasculopathy, myelitis, inflammatory bowel disease, perforated ulcers, and gastritis. The actual disease burden of varicella is not known as most of the infected individuals may not visit the physician. The amplifiable VZV DNA will not always be detectable in cerebrospinal fluid (CSF) samples in protracted illnesses such as vasculopathies, but demonstrable anti-VZV IgG in CSF has diagnostic value. The World Health Organization (WHO) position paper 2014 recommends two doses of varicella and zoster vaccines in targeted population. In India, varicella vaccine is not included in the UIP due to the cost and the belief that lifelong immunity occurs following primary infection. The expanded spectrum of VZV disease and the mounting body of evidence, however, suggest the need for both varicella and zoster vaccines in routine immunization schedule.

Effectiveness of the varicella vaccine in the real world, a matched case-control study

BACKGROUND

Universal varicella vaccination has been introduced in many countries, but there are a number of important differences in their vaccination strategies. It is essential to establish a vaccination program that can maximize the benefits of varicella vaccine, but there is a lack of comprehensive research on the effectiveness of varicella vaccine in different vaccination status.

METHODS

Using data from population-based surveillance platforms we conducted a 1:2 matched case-control study. The cases were clinically diagnosed varicella with onset from 2017 to 2021, 1-14 years old in Chaoyang District, Beijing. The controls were matched according to date of birth (±1 month), sex and residence. The vaccination data of the subjects were obtained from the Childhood Immunization Information Management System in Beijing. Using conditional logistic regression models with or without interaction terms, we evaluated the effectiveness of varicella vaccine in different vaccination status.

RESULTS

A total of 2528 cases and 5056 controls were enrolled. This study found that whether the time since last vaccination was adjusted had a substantial effect on the comparing vaccine effectiveness (VE) between subgroups. After adjustment for the time since last vaccination, 1) the incremental VE of 2-dose was 49.6 % (95 % Confidence Interval [CI], 38.8-58.6) compared with 1-dose (93.9 % vs. 88.0 %); 2) Among children who received one dose, the risk of chickenpox in children vaccinated at 18-23 months was 1.382 (95 %CI, 1.084-1.762) times that in children vaccinated at 12-17 months. 3) the VE with less than one, two, and three year intervals is higher than that with six-year-intervals (P < 0.05), respectively.

CONCLUSIONS

When comparing VE between subgroups of different vaccination status, the time since last vaccination should be adjusted. The first dose of varicella vaccine should be given as early as the second year of life, and the second dose can improve vaccine effectiveness.

The epidemiologic and economic impact of varicella and herpes zoster vaccination in South Korea: A mathematical modelling study

BACKGROUND

In South Korea, the National Immunization Program has included one-dose varicella vaccination for 1-year-olds since 2005. This study examines the potential impact of introducing a two-dose varicella vaccination for children, along with zoster vaccination for adults, using either the zoster vaccine live (ZVL) or recombinant zoster vaccine (RZV).

METHODS

The investigation considered four strategies in a base case scenario. The first involved introducing zoster vaccination for 60-year-olds, with a 60 % coverage. The second strategy combined zoster vaccination with a second-dose varicella vaccination for 4-year-olds, with a 90 % coverage. An age-structured model spanning 50 years was employed, assuming a zoster vaccine catch-up campaign over the initial 5 years. Cost-effectiveness analyses were conducted, assessing incremental cost-effectiveness ratios (ICERs), incremental net monetary benefits (INMBs), and net loss under different ages at zoster vaccination (50, 60, 65, and 70 years) and varying willingness-to-pay (WTP) levels from ₩40 million ($34,998) to ₩84 million ($74,000).

RESULTS

All strategies were cost-effective and significantly reduced herpes zoster (HZ) incidence, preventing approximately 3,077,000 to 7,609,000 cases, depending on the chosen strategy. The combined strategy prevented around 4,950,000 varicella and 653,000 HZ cases additionally. RZV outperformed ZVL by preventing twice as many HZ cases and offering greater QALY gains. However, ZVL was more cost-effective due to its lower cost. Probabilistic sensitivity analyses revealed that RZV became more cost-effective at higher WTP thresholds, exceeding ₩60.9 million ($53,193) in terms of ICER and ₩62.5 million ($54,591) for INMBs and net loss. The optimal age for zoster vaccination was 60 years concerning ICER but 50 years regarding INMB.

CONCLUSIONS

Combining RZV with a two-dose varicella vaccination strategy reduced the disease burden and improved QALY more effectively, though ZVL remained more cost-effective at lower WTP levels. Decisions regarding vaccination policies should be balanced between the public health needs and WTP levels.

Economic burden of varicella in Bangkok, Thailand: A multicenter medical chart review study

Our multicenter, medical chart review, cost-of-illness study used a micro-costing approach to evaluate the economic burden associated with varicella in Bangkok, Thailand, from a societal perspective. We reviewed medical charts of adults and children with a primary diagnosis of varicella (2014-2018) from 4 hospitals in Bangkok. Reported healthcare resource utilization and missed school or workdays were extracted from medical charts. Mean direct, indirect, and total costs per patient were estimated for overall, adult, and pediatric patients (2020 USD). Of the 200 children and 60 adults, 99.6%, 5.4%, and 5.4% had a varicella-related outpatient visit, emergency department visit, and hospitalization, respectively. The mean direct medical cost was 33 USD for pediatric and adult patients. The mean cost of outpatient visits (8 vs 13 USD, P<0.001) and medications (7 vs 9 USD, P<0.001) was significantly lower among pediatric patients. Forty-eight children reported a mean of 5.8 school days lost, and 32 adult patients reported a mean of 7.4 workdays lost. The mean total cost per varicella patient was 89 USD, with the mean total cost higher for adult than pediatric patients (145 vs 72 USD, P<0.001). Indirect cost accounted for 63% of the total cost per patient (54% for pediatric patients and 77% for adult patients). There is a substantial economic burden associated with patients seeking varicella-related healthcare in Thailand, including considerable indirect costs.

Effectiveness of two-dose vs. one-dose varicella vaccine in children in Shanghai, China: a prospective cohort study

Objective

Varicella, a highly contagious viral disease caused by the varicella-zoster virus (VZV), affects millions globally, with a higher prevalence among children. After the initial infection, VZV lies dormant in sensory ganglia and has the potential to reactivate much later, causing herpes zoster (HZ). Vaccination is one of the most effective methods to prevent varicella, and the two-dose varicella vaccine (VarV) regimen is widely used around the world. In China, the VarV has been included in the national immunization programme with a recommended single-dose regimen. This study aimed to compare the effectiveness of the two-dose vs. one-dose VarV regimen in children in Shanghai, China.

Materials and methods

A prospective cohort study was conducted in Shanghai, China, from September 2018 to December 2022. The study enrolled children aged 3-18 years who had received either the one-dose, two-dose, or 0-dose VarV regimen. Vaccination history, varicella infection status, and relevant variables, including demographic information (name, date of birth and sex) and medical history (clinical features of varicella and illness duration) were collected through medical record review and parental interviews.

Results

A total of 3,838 children were included in the study, with 407 in the 0-dose regimen group, 2,107 in the one-dose regimen group and 1,324 in the two-dose regimen group. The corresponding incidence density in these groups was 0.13, 0.05 and 0.03 cases per 1,000 person-days, respectively. The adjusted vaccine effectiveness (VE) was 81.7% (95%CI: 59.3-91.8%) for the two-dose regimen and 60.3% (95%CI: 29.3-77.7%) for the one-dose regimen, compared to the 0-dose regimen. The two-dose VarV regimen showed a protective effectiveness of 47.6% (95%CI: 2.5-71.9%) compared to the one-dose VarV regimen.

Conclusion

This study provides evidence supporting the greater effectiveness of the two-dose VarV regimen in preventing varicella infection compared to the one-dose regimen.

The clinical and economic costs associated with regional disparities in varicella vaccine coverage in Italy over 50 years (2020-2070)

Italy implemented two-dose universal varicella vaccination (UVV) regionally from 2003 to 2013 and nationally from 2017 onwards. Our objective was to analyze regional disparities in varicella outcomes resulting from disparities in vaccine coverage rates (VCRs) projected over a 50-year time-horizon (2020-2070). A previously published dynamic transmission model was updated to quantify the potential public health impact of the UVV program in Italy at the national and regional levels. Four 2-dose vaccine strategies utilizing monovalent (V) and quadrivalent (MMRV) vaccines were evaluated for each region: (A) MMRV-MSD/MMRV-MSD, (B) MMRV-GSK/MMRV-GSK, (C) V-MSD/MMRV-MSD, and (D) V-GSK/MMRV-GSK. Costs were reported in 2022 Euros. Costs and quality-adjusted life-years (QALYs) were discounted 3% annually. Under strategy A, the three regions with the lowest first-dose VCR reported increased varicella cases (+ 34.3%), hospitalizations (+ 20.0%), QALYs lost (+ 5.9%), payer costs (+ 22.2%), and societal costs (+ 14.6%) over the 50-year time-horizon compared to the three regions with highest first-dose VCR. Regions with low first-dose VCR were more sensitive to changes in VCR than high first-dose VCR regions. Results with respect to second-dose VCR were qualitatively similar, although smaller in magnitude. Results were similar across all vaccine strategies.

UK healthcare professionals' attitudes towards the introduction of varicella vaccine into the routine childhood vaccination schedule and their preferences for administration

BACKGROUND

Varicella (chickenpox) is a highly contagious disease caused by the varicella-zoster virus. Although typically mild, varicella can cause complications leading to severe illness and even death. Safe and effective varicella vaccines are available. The Joint Committee on Vaccination and Immunisation has reviewed the evidence and recommended the introduction of varicella vaccine into the UK's routine childhood immunisation schedule.

OBJECTIVES

To explore UK healthcare professionals' (HCPs) knowledge and attitudes towards varicella vaccination, its introduction to the UK routine childhood immunisation schedule, and their preferences for how it should be delivered.

DESIGN

We conducted an online cross-sectional survey exploring HCPs' attitudes towards varicella, varicella vaccine, and their preferences for delivery of the vaccine between August and September 2022 prior to the recommendation that varicella vaccine should be introduced.

PARTICIPANTS

91 HCPs working in the UK (81 % nurses/health visitors, 9 % doctors, 10 % researcher/other, mean age 48.7 years).

RESULTS

All respondents agreed or strongly agreed that vaccines are important for a child's health. However, only 58% agreed or strongly agreed that chicken pox was a disease serious enough to warrant vaccination. Gaps in knowledge about varicella were revealed: 21.0% of respondents disagreed or were unsure that chickenpox can cause serious complications, while 41.8% were unsure or did not believe chickenpox was serious enough to vaccinate against. After receiving some basic information about chickenpox and the vaccine, almost half of the HCPs (47.3%) in our survey would prefer to administer the varicella vaccine combined with MMR.

CONCLUSIONS

Given the positive influence of HCPs on parents' decisions to vaccinate their children, it is important to understand HCPs' views regarding the introduction of varicella vaccine into the routine schedule. Our findings highlighted areas for training and HCPs' preferences which will have implications for policy and practice when the vaccine is introduced.

Varicella outbreak at nursery school under routine immunization in Japan in 2017 and 2018 and vaccine effectiveness

BACKGROUND

In Japan, routine administration to one-year-old children of two-dose immunization for varicella was introduced in October 2014. Object The object of this study was to report outbreaks of varicella under routine immunization at a nursery school and in its surrounding area using data of surrounding areas from the (Nursery) School Absenteeism Surveillance System. Then, we measured the effectiveness of routine two-dose immunization for varicella to onset. We tentatively assessed its severity in a nursery school.

METHOD

The study period extended from April 2017 through March 2018. The study area comprised Nursery school B and other nursery schools, and elementary and junior high schools in City A. Subjects in Nursery school B were 120 children. We analyzed vaccine effectiveness (VE) as an observational study and assessed severity using Fisher's exact test. We also assessed VE for severity using linear regression. Severity was defined as the length of nursery school absence attributable to varicella infection.

RESULTS

During the one month preceding a period of two weeks before the initial case at Nursery school B, there were 16 cases of varicella infection in nursery schools, 45 cases in elementary schools, and one case in junior high schools in City A. For children who had received one vaccine dose or more, VE was 48.1% for all ages and 49.2% among children three years old and older. No significant VE against infection was found. Vaccination using one dose or more can reduce severity significantly.

DISCUSSION AND CONCLUSION

Because many nursery school children who had received two doses of vaccine were infected, VE was estimated as low in the nursery school and not significant. Although VE for severity with more than one dose was confirmed, a second dose might not reduce severity compared to one dose.

Epidemiological Characteristics of Varicella in Anhui Province, China, 2012-2021: Surveillance Study

BACKGROUND

Varicella is a mild, self-limited disease caused by varicella-zoster virus (VZV) infection. Recently, the disease burden of varicella has been gradually increasing in China; however, the epidemiological characteristics of varicella have not been reported for Anhui Province.

OBJECTIVE

The aim of this study was to analyze the epidemiology of varicella in Anhui from 2012 to 2021, which can provide a basis for the future study and formulation of varicella prevention and control policies in the province.

METHODS

Surveillance data were used to characterize the epidemiology of varicella in Anhui from 2012 to 2021 in terms of population, time, and space. Spatial autocorrelation of varicella was explored using the Moran index (Moran I). The Kulldorff space-time scan statistic was used to analyze the spatiotemporal aggregation of varicella.

RESULTS

A total of 276,115 cases of varicella were reported from 2012 to 2021 in Anhui, with an average annual incidence of 44.8 per 100,000, and the highest incidence was 81.2 per 100,000 in 2019. The male-to-female ratio of cases was approximately 1.26, which has been gradually decreasing in recent years. The population aged 5-14 years comprised the high-incidence group, although the incidence in the population 30 years and older has gradually increased. Students accounted for the majority of cases, and the proportion of cases in both home-reared children (aged 0-7 years who are not sent to nurseries, daycare centers, or school) and kindergarten children (aged 3-6 years) has changed slightly in recent years. There were two peaks of varicella incidence annually, except for 2020, and the incidence was typically higher in the winter peak than in summer. The incidence of varicella in southern Anhui was higher than that in northern Anhui. The average annual incidence at the county level ranged from 6.61 to 152.14 per 100,000, and the varicella epidemics in 2018-2021 were relatively severe. The spatial and temporal distribution of varicella in Anhui was not random, with a positive spatial autocorrelation found at the county level (Moran I=0.412). There were 11 districts or counties with high-high clusters, mainly distributed in the south of Anhui, and 3 districts or counties with high-low or low-high clusters. Space-time scan analysis identified five possible clusters of areas, and the most likely cluster was distributed in the southeastern region of Anhui.

CONCLUSIONS

This study comprehensively describes the epidemiology and changing trend of varicella in Anhui from 2012 to 2021. In the future, preventive and control measures should be strengthened for the key populations and regions of varicella.

Effectiveness of the combined MMRV Priorix-Tetra™ vaccine against varicella in a large Italian region: A case-control study

Priorix-Tetra™ (MMRV GlaxoSmithKline Biologicals' vaccine) was developed based on the existing measles-mumps-rubella and varicella vaccines. In this study, we aimed to estimate the effectiveness of the combined measles-mumps-rubella-varicella Priorix-Tetra™ vaccine against varicella in real-world conditions. We conducted a post-marketing retrospective case-control study in the Apulia region of Italy in children aged 1-9 years born between January 1, 2008 and December 31, 2016. We assessed the effectiveness against varicella of all grades of severity (including hospitalisation) and against hospitalisation for varicella of a single and two doses of Priorix-Tetra™. Moreover, we also assessed effectiveness of monovalent varicella (monovalent-V) vaccine and any varicella vaccines. Vaccine effectiveness was calculated as (1-OR) x 100. We introduced demographic variables in the model to adjust Vaccine effectiveness (aVE) by potential confounders (sex and year of birth). We recorded 625 varicella cases and matched them with 1,875 controls. Among 625 cases, 198 had received a single MMRV dose, 10 two MMRV doses, 46 a single monovalent-V dose, none two monovalent-V doses; four a monovalent-V as first dose and MMRV as second dose, and one a MMRV as first dose and monovalent-V as second dose; 366 cases were not vaccinated. The aVE against varicella of all grades of severity was 77.0% and 93.0% after a single dose and after two doses of MMRV, respectively. The aVE against varicella of all grades was 72.0% after a single dose of monovalent-V vaccine. The aVE against varicella of all grades of severity was 76.0% after a single dose and 94.0% after two doses of any varicella vaccine. The aVE against varicella hospitalisation was 96% after a single dose of any varicella vaccine. Priorix-Tetra™ showed to be an effective vaccine and the two-dose schedule should be recommended to optimise immunisation programmes. A single dose was able to provide protection against varicella hospitalisation.

Prevalence and progression of pneumonia in immunocompetent adults with varicella

Pneumonia is the most common complication of varicella infections. Although previous studies have tended to focus mainly on immunocompromised patients, varicella pneumonia can also occur in healthy adults. Therefore, in this study, we aimed to assess the progression of varicella pneumonia in immunocompetent hosts. This retrospective study involved immunocompetent adult outpatients with varicella who attended the adult Fever Emergency facility of Peking University Third Hospital from April 1, 2020, to October 31, 2022. Varicella pneumonia was defined as a classic chickenpox-type rash in patients with infiltrates on chest computed tomography. The study included 186 patients, 57 of whom had a contact history of chickenpox exposure. Antiviral pneumonia therapy was administered to 175 patients by treating physicians. Computed tomography identified pneumonia in 132 patients, although no deaths from respiratory failure occurred. Seventy of the discharged patients were subsequently contacted, all of whom reported being well. Follow-up information, including computed tomography findings, was available for 37 patients with pneumonia, among whom 24 reported complete resolution whereas the remaining 13 developed persistent calcifications. Notably, we established that the true incidence of varicella pneumonia is higher than that previously reported, although the prognosis for immunocompetent hosts is generally good.

Parental perceptions of chickenpox and the varicella vaccine: A qualitative systematic review

BACKGROUND

In countries where varicella vaccination is not on the routine childhood immunisation schedule, such as those in the United Kingdom (UK), chickenpox is an almost universal disease of childhood. Chickenpox can cause serious complications, particularly in infants, pregnant women, and the immunocompromised. In November 2023 the varicella vaccine was recommended for inclusion in the UK routine childhood immunisation schedule. Successful rollout of the vaccine may be hindered by parental concerns about vaccine safety and efficacy, and perceptions of chickenpox as a mild illness.

OBJECTIVE

To examine parental perceptions of chickenpox and varicella vaccination, which may be crucial to effective vaccination campaigns.

DESIGN

Qualitative systematic review and thematic analysis.

METHODS

Six electronic databases were systematically searched for studies published between 2016 and 2023: CINAHL, EMBASE, MEDLINE, PsycInfo, PubMed, and Web of Science. The included studies were appraised against the Critical Appraisal Skills Program checklist for qualitative studies. Thematic analysis was used to analyse qualitative data, through the development of themes.

RESULTS

22 articles were included in this review, and five themes identified: perceptions that chickenpox is a mild illness, that parents have concerns about varicella vaccine efficacy and safety, a notion of natural immunity as superior, social determinants of health influence vaccine decision making, and vaccination is overwhelming perceived as a parental decision.

CONCLUSIONS

Whilst some parents displayed an acceptance and willingness to vaccinate against chickenpox, many expressed concerns, and perceived chickenpox as a routine unworrying childhood illness. Analysis demonstrated a knowledge gap in understanding UK parental opinions regarding chickenpox and varicella vaccination, highlighting the need for research in this area, particularly given ongoing reconsideration for inclusion in the UK vaccination schedule.

REGISTRATION

The review was registered on PROSPERO, registration ID CRD42021236120.

Immunogenicity and safety of a live attenuated varicella vaccine co-administered with inactive hepatitis A vaccine: A phase 4, single-center, randomized, controlled trial

Co-administration of vaccines can facilitate the introduction of new vaccines in immunization schedules. This study aimed to evaluate the immunogenicity and safety of co-administration with live attenuated varicella vaccine (VarV) and inactivated hepatitis A vaccine (HepA) among children aged 12 ~ 15 months. In this phase 4 clinical trial, 450 children were randomized with a ratio of 1:1 to receive VarV and Hep A simultaneously (Group A) or separately (Group B). The primary endpoints were the seroconversion rate of anti-varicella-zoster virus (VZV) antibodies 42 days after vaccination of VarV and the seroconversion rate of anti-Hepatitis A virus (HAV) antibodies 30 days after two-dose vaccination of HepA. After full immunization, the seroconversion rates of anti-VZV antibodies were 91.79% in Group A and 92.15% in Group B; the geometric mean titers (GMTs) were 11.80 and 12.19, respectively. The seroconversion rates of anti-HAV antibodies were 99.48% in Group A and 100.0% in Group B; the geometric mean concentrations (GMCs) reached 9499.11 and 9528.36 mIU/ml, respectively. The lower limits of the 95% CI for the seroconversion difference of anti-VZV antibodies and anti-HAV antibodies were -5.86% and -2.90%, which greater than the predefined non-inferiority margin (-10%). The incidence rate of adverse reactions in Group A was lower than Group B (9.33% vs 16.22%), and only one serious adverse event was reported in Group B, which was unrelated to the study vaccine. In conclusion, the co-administration of VarV with HepA has non-inferior immunogenicity and safety profiles were quite comparable with the separate administration of both vaccines.Trial registration number: NCT05526820 (ClinicalTrials.gov).

Assessing the impact of chickenpox and shingles vaccination using intermittent enhanced surveillance in Queensland, Australia

INTRODUCTION

Chickenpox and shingles are vaccine preventable diseases caused by varicella-zoster virus (VZV). Chickenpox is more common in children before adolescence and shingles among ≥50 years of age. With this study we aimed to determine changes in VZV epidemiology following chickenpox and shingles vaccine introduction in Queensland.

METHODS

This case series study used notified cases of VZV infection in Queensland from January 2010 to December 2021. In Queensland, VZV notifications are received as mostly clinically unspecified cases from pathology laboratories. Intermittent enhanced surveillance was conducted using clinician follow up to determine chickenpox and shingles clinical presentation, and we then analysed these by age-group, time period, and within vaccine eligible cohorts.

RESULTS

Of the 87,759 VZV notifications received, 70 % (n = 61,298) were notified as unspecified, followed by 23 % shingles (n = 19,927), and 7 % chickenpox (n = 6,534). Over the study period, the percent change in total notifications adjusted by age and sex was estimated to be an increase of 5.7 % (95 % CI 4.9-6.4) each year. The chickenpox notifications fell sharply at 18 months of age (eligible for chickenpox vaccine) with the rate being 57 % and 36 % lower among those aged 18-23 months compared to <12 and 12-17 months of age, respectively. Assuming all cases aged 60 years and older were shingles, notification rates of shingles decreased by 12-22 % among 70-79 years old (eligible for shingles vaccination) over the years 2017-2021 after vaccine introduction in 2016.

CONCLUSION

The VZV notification rate has increased over time in Queensland. Impact of chickenpox and shingles vaccines funded under National Immunisation Program is seen with a decline in notification rates among age-specific cohorts eligible to receive the vaccines under the program. Introduction of a second childhood dose chickenpox vaccine and more effective recombinant shingles vaccine may further improve the impact of the vaccination program.

A single-dose strategy for immunization with live attenuated vaccines is an effective option before treatment initiation in multiple sclerosis patients

BACKGROUND

Mumps-Measles-Rubella (MMR) and Varicella zoster vaccines (VAR) are live attenuated vaccines, usually administered in a two-dose scheme at least 4 weeks apart. However, single-dose immunization schemes may also be effective and can reduce delays in immunosuppressive treatment initiation in patients with multiple sclerosis (pwMS) who need to be immunized.

OBJECTIVES

To evaluate the immunogenicity of a single-dose attempt (SDA) versus the standard immunization scheme (SIS) with VAR and/or MMR in pwMS.

METHODS

Retrospective observational study in pwMS vaccinated against VAR and/or MMR. We compared seroprotection rates and antibody geometric mean titers (GMTs) between the two strategies.

RESULTS

Ninety-six patients were included. Thirty-one patients received VAR and 67 MMR. In the SDA group, the seroprotection rate was 66.7% (95% confidence interval (CI): 53.3-78.3) versus 97.2% (95% CI: 85.5-99.9) in the SIS (p < 0.001). For the seroprotected patients, GMTs were similar for both schemes.

CONCLUSION

An SDA of VAR and/or MMR vaccines could be sufficient to protect almost two-thirds of patients. Testing immunogenicity after a single dose of VZ and/or MMR could be included in routine clinical practice to achieve rapid immunization.

Safety and immunogenicity of the live-attenuated varicella vaccine in pediatric solid organ transplant recipients: A systematic review and meta-analysis

This study aimed to synthesize the available evidence on the immunogenicity, safety, and effectiveness of live-attenuated varicella vaccine in solid organ transplant recipients. Medline and EMBASE were searched using predefined search terms to identify relevant studies. The included articles reported varicella vaccine administration in the posttransplant period in children and adults. A pooled proportion of transplant recipients who seroconverted and who developed vaccine-strain varicella and varicella disease was generated. Eighteen articles (14 observational studies and 4 case reports) were included, reporting on 711 transplant recipients who received the varicella vaccine. The pooled proportion was 88.2% (95% confidence interval 78.0%-96.0%, 13 studies) for vaccinees who seroconverted, 0% (0%-1.2%, 13 studies) for vaccine-strain varicella, and 0.8% (0%-4.9%, 9 studies) for varicella disease. Most studies followed clinical guidelines for administering live-attenuated vaccines, with criteria that could include being at least 1 year posttransplant, 2 months postrejection episode, and on low-dose immunosuppressive medications. Varicella vaccination in transplant recipients was overall safe in the included studies, with few cases of vaccine-strain-induced varicella or vaccine failure, and although it was immunogenic, the proportion of recipients who seroconverted was lower than that seen in the general population. Our data support varicella vaccination in select pediatric solid organ transplant recipients.

Impact of Varicella Immunization and Public Health and Social Measures on Varicella Incidence: Insights from Surveillance Data in Shanghai, 2013-2022

To evaluate the impact of a two-dose VarV program on varicella incidence among the whole population, considering the influence of public health and social measures (PHSMs), we extracted surveillance data on varicella cases during 2013-2022 in Minhang, Shanghai. Then, we estimated the incidence trend of varicella through interrupted time-series analyses and quantified the impact of the immunization program and PHSMs using Serfling regression. We also explored the associations between PHSMs and varicella cases. The implementation of the two-dose VarV strategy was followed by a significant decrease in varicella incidence (-1.84% per month). After one year of the program, varicella incidence was estimated at a 45.25% reduction, which was higher in children (59.12% and 54.09%) than in adults (19.49%). The decrease attributed to PHSMs was 31.26% during 2020-2022, and school closing was identified as the most relevant PHSM (b = -8.03 cases, r = -0.67 with a 1-week lag). These findings indicate that the two-dose immunization program has more effectively reduced the varicella incidence compared with the one-dose vaccine, and interventions like school closings are also encouraged to serve as supplementary measures to prevent varicella epidemics.

Real-World Effectiveness of the Varicella Vaccine among Children and Adolescents in Qatar: A Case-Control Study

BACKGROUND

Despite the availability of a highly efficacious vaccine, varicella outbreaks are still being reported globally. In this study, we evaluated the real-world effectiveness of varicella vaccination among children between the ages of 1 and 18 years old during the period 2017 to 2019 in Qatar.

METHODS

A matched case-control study was conducted that included all reported varicella-infected children who visited the primary healthcare system in Qatar from January 2017 to December 2019. The cases were children under the age of 18 years who were clinically diagnosed with varicella. The controls were of the same age, who visited the Primary Health Care Corporation (PHCC) during 2017-2019 with a skin rash where varicella infection was ruled out. The data on varicella vaccination for each participant were obtained from the electronic database in the PHCC during the study period.

RESULTS

We included 862 cases of varicella and 5454 matched controls, with a median age of 8 years (IQR 3-12); 47.4% were female and almost 50% were of Qatari nationality. The year 2019 had the highest varicella infection count with a total of 416 cases. The cases were less likely to be vaccinated against varicella, with approximately a quarter (25.6%) of cases and 36.7% of the controls having either one or two doses of the vaccine (p < 0.001). Compared to not being vaccinated, a single dose vaccination showed a 56% reduction in the odds of varicella infection [OR 0.44, 95% CI: 0.34-0.55; p < 0.000], and a two-dose vaccination showed an 86% reduction in the odds of varicella infection [OR 0.13, 95% CI: 0.06-0.29; p < 0.000].

CONCLUSION

In this multicultural setting, a two-dose varicella vaccination shows reasonable protection against varicella infection.

The epidemiology of varicella and effectiveness of varicella vaccine in Ganyu, China: a long-term community surveillance study

BACKGROUND

The real-world data of long-term protection under moderate vaccination coverage is limited. This study aimed to evaluate varicella epidemiology and the long-term effectiveness under moderate coverage levels in Ganyu District, Lianyungang City, Jiangsu Province.

METHODS

This was a population-based, retrospective birth cohort study based on the immunization information system (IIS) and the National Notifiable Disease Surveillance System (NNDSS) in Ganyu District. Varicella cases reported from 2009 to 2020 were included to describe the epidemiology of varicella, and eleven-year consecutive birth cohorts (2008-2018) were included to estimate the vaccine effectiveness (VE) of varicella by Cox regression analysis.

RESULTS

A total of 155,232 native children and 3,251 varicella cases were included. The vaccination coverage was moderate with 37.1%, correspondingly, the annual incidence of varicella infection increased 4.4-fold from 2009 to 2020. A shift of the varicella cases to older age groups was observed, with the peak proportion of cases shifting from 5-6 year-old to 7-8 year-old. The adjusted effectiveness of one dose of vaccine waned over time, and the adjusted VE decreased from 72.9% to 41.8% in the one-dose group.

CONCLUSIONS

The insufficient vaccination coverage (37.1%) may have contributed in part to the rising annual incidence of varicella infection, and a shift of varicella cases to older age groups occurred. The effectiveness of one dose of varicella vaccine was moderate and waned over time. It is urgent to increase varicella vaccine coverage to 80% to reduce the incidence of varicella and prevent any potential shift in the age at infection in China.

Posterior Herpetic Uveitis: A Comprehensive Review

PURPOSE

To report and illustrate the main clinical presentations of posterior herpetic uveitis.

METHODS

Narrative review.

RESULTS

The ocular manifestations of posterior herpetic uveitis include different clinical presentations. Herpes simplex and varicella zoster can cause acute retinal necrosis, progressive outer retinal necrosis, and non-necrotizing herpetic retinopathies. Cytomegalovirus has been associated with fulminant retinitis with confluent areas of retinal necrosis and retinal hemorrhages, indolent/granular retinitis, and frosted branch angiitis. These diverse clinical presentations are often associated with specific risk factors and different immunological profiles of the host.

CONCLUSIONS

Herpetic viruses can cause posterior uveitis, presenting various clinical findings. Specific ocular manifestations and the immunological status of the host can help to differentiate the various herpetic entities before laboratory tests confirm the diagnosis.

Advances in Alpha Herpes Viruses Vaccines for Human

Alpha herpes simplex viruses are an important public health problem affecting all age groups. It can produce from common cold sores and chicken pox to severe conditions like encephalitis or newborn mortality. Although all three subtypes of alpha herpes viruses have a similar structure, the produced pathology differs, and at the same time, the available prevention measures, such as vaccination. While there is an available and efficient vaccine for the varicella-zoster virus, for herpes simplex virus 1 and 2, after multiple approaches from trivalent subunit vaccine to next-generation live-attenuated virus vaccines and bioinformatic studies, there is still no vaccine available. Although there are multiple failed approaches in present studies, there are also a few promising attempts; for example, the trivalent vaccine containing herpes simplex virus type 2 (HSV-2) glycoproteins C, D, and E (gC2, gD2, gE2) produced in baculovirus was able to protect guinea pigs against vaginal infection and proved to cross-protect against HSV-1. Another promising vaccine is the multivalent DNA vaccine, SL-V20, tested in a mouse model, which lowered the clinical signs of infection and produced efficient viral eradication against vaginal HSV-2. Promising approaches have emerged after the COVID-19 pandemic, and a possible nucleoside-modified mRNA vaccine could be the next step. All the approaches until now have not led to a successful vaccine that could be easy to administer and, at the same time, offer antibodies for a long period.

Antimicrobial use for the management of varicella in Thailand: a retrospective observational study

OBJECTIVE

To describe the clinical characteristics of varicella patients seeking medical consultation and the use of antimicrobials for their management in Thailand in the absence of universal varicella vaccination (UVV).

METHODS

A multicenter, retrospective chart review of 260 children and adults with a primary diagnosis of varicella was conducted at one private and three public hospitals in Bangkok, Thailand. Charts of varicella patients (inpatient or outpatient) were randomly selected over a 5-year period. Key outcomes included clinical complications and the use of antibiotics, antivirals, and other medications.

RESULTS

Charts of 200 children (mean age 5.7 years, range 0.3-16 years) and 60 adults (mean age 27.9 years, range 18-50 years) were reviewed. Fourteen patients (including 8 children) were hospitalized. Five percent of the children and none of the adults were immunocompromised. At least 1 varicella-related complication was reported by 7.3% (7% of children, 8.3% of adults, p = .778) of all patients, including 57.1% (62.5% of children, 50% of adults) of inpatients (p < .001, compared with outpatients). Skin/soft tissue infection (47.7%) and dehydration (47.4%) were the most common complications. Antivirals (mainly oral acyclovir) were prescribed to 46.5% of patients (31.5% of children, 96.7% of adults, p < .001). Antibiotics were prescribed to 20.8% of patients (19% of children, 26.7% of adults, p = .199). Topical, oral, and intravenous antibiotics were prescribed to 12.3%, 8.5%, and 1.2% of patients, respectively. Antimicrobial prescriptions were higher among adults (p < .001) and immunocompromised patients (p = .025). Apart from antimicrobials, acetaminophen (62.3%) and oral antihistamines (51.5%) were the most prescribed.

CONCLUSION

A considerable number of varicella patients, both children and adults, seeking medical consultation in Thai hospitals are prescribed antibiotics and antivirals, with one-fifth of patients being prescribed an antibiotic and almost half prescribed an antiviral. The study may be of interest to policymakers in Thailand and other Asia-Pacific countries considering UVV implementation.

The necessity for popularizing varicella-zoster virus vaccine programs worldwide: An age-period-cohort analysis for the Global Burden of Disease study 2019

BACKGROUND

Varicella-zoster virus (VZV) causes varicella and herpes zoster (VHZ), which is endemic worldwide. Although infection with VZV represents a considerable health threat, the global, regional and national burden of VZV infection, especially the probable relationship between VZV vaccines and the epidemiology of VZV infection, is poorly known. We sought to estimate the global spatial patterns and temporal trends of VHZ burden in 204 countries and territories from 1990 to 2019.

METHODS

Numbers and age-standardized rates (ASR) of VHZ incidence, and disability-adjusted life years (DALYs) were estimated using data from the Global Burden of Diseases Study (GBD) 2019. Spatiotemporal trends in ASR were evaluated by estimated annual percentage change (EAPC).

RESULTS

Worldwide, in 2019, there were approximately 84.0 million incidence and 0.9 million DALYs due to VHZ. The corresponding ASIR (age-standardized incidence rate) and ASDR (age-standardized DALY rate) drastically decreased in children (aged <20 years old), while the ASIR and ASDR of VHZ significantly increased in middle- and old-aged adults (aged >50 years old), with highest ASIR and ASDR in the High-income Asia Pacific and Western Sub-Saharan Africa, respectively. From 1990-2019, the corresponding EAPC in ASIR were 0.03 (95% uncertainty interval [UI]: 0.02-0.04). Whereas the global EAPC in ASDR decreased in all regions (-1.59, 95% UI: -1.64 to -1.55), expect for Australasia (0.46, [0.05, 0.88]). Notably, in 2019, age-specific rates of VHZ DALYs presented a rapid growth trend after 70 years old.

CONCLUSION

The spatiotemporal trends of VHZ were heterogeneous across countries from 1990 to 2019. The spatiotemporal trend in ASIR is highest in the High sociodemographic index (SDI) region, however the EAPC in ASDR is lowest, in part probably due to VHZ vaccination. Therefore, reducing morbidity and burden strategies such as vaccines programs for the prevention of VHZ should be promoted in those regions with high growth incidence and/or burden, especially for the population after 70 years old.

The Protective Effectiveness of 2-Dose Varicella Vaccination in Children in Korea: A Case-Control Study

BACKGROUND

A 2-dose vaccination against varicella has been adopted in many places; however, it has not been widely introduced in Korea. This study aimed to assess 1-dose and 2-+dose vaccine effectiveness (VE) against laboratory-confirmed varicella in Korea to provide a scientific basis for developing an immunization strategy.

METHODS

We constructed a national cohort using national surveillance data and the national immunization registry. From the cohort, we conducted a 1:2 matched nested case-control study to estimate and compare the VE of the 1-dose and 2-dose of varicella vaccination using exact conditional logistic regression. VE was calculated as [1 - matched odds ratio (OR) × 100%].

RESULTS

From January 1, 2011 to December 31, 2020, a total of 205,173 varicella cases were reported to the notifiable diseases surveillance system. Of these, we included 4,387 laboratory-confirmed varicella cases and 8,774 controls for the analyses. The VE of 1-dose vaccination was 16.8% (95% CI: -9.0% to 36.5%), whereas the VE of 2-doses of the vaccination was 98.6% (95% CI: 96.0%-99.5%).

CONCLUSION

These findings suggest that the 2-dose vaccination strategy can be an effective strategy to prevent varicella.

Universal varicella vaccination in Denmark: Modeling public health impact, age-shift, and cost-effectiveness

We modeled the long-term clinical and economic impact of two-dose universal varicella vaccination (UVV) strategies in Denmark using a dynamic transmission model. The cost-effectiveness of UVV was evaluated along with the impact on varicella (including age-shift) and herpes zoster burden. Six two-dose UVV strategies were compared to no vaccination, at either short (12/15 months) or medium (15/48 months) intervals. Monovalent vaccines (V-MSD or V-GSK) for the 1st dose, and either monovalent or quadrivalent vaccines (MMRV-MSD or MMRV-GSK) for the 2nd dose were considered. Compared to no vaccination, all two-dose UVV strategies reduced varicella cases by 94%-96%, hospitalizations by 93%-94%, and deaths by 91%-92% over 50 years; herpes zoster cases were also reduced by 9%. There was a decline in the total number of annual varicella cases in all age groups including adolescents and adults. All UVV strategies were cost-effective compared to no vaccination, with ICER values ranging from €18,228-€20,263/QALY (payer perspective) and €3,746-€5,937/QALY (societal perspective). The frontier analysis showed that a two-dose strategy with V-MSD (15 months) and MMRV-MSD (48 months) dominated all other strategies and was the most cost-effective. In conclusion, all modeled two-dose UVV strategies were projected to substantially reduce the clinical and economic burden of varicella disease in Denmark compared to the current no vaccination strategy, with declines in both varicella and zoster incidence for all age groups over a 50-year time horizon.

Parental acceptance of and preferences for administration of routine varicella vaccination in the UK: A study to inform policy

OBJECTIVES

To explore acceptability of and preferences for the introduction of varicella vaccination to the UK childhood immunisation schedule.

DESIGN

We conducted an online cross-sectional survey exploring parental attitudes towards vaccines in general, and varicella vaccine specifically, and their preferences for how the vaccine should be administered.

PARTICIPANTS

596 parents (76.3% female, 23.3% male, 0.4% other; mean age 33.4 years) whose youngest child was aged 0-5 years.

MAIN OUTCOME MEASURES

Willingness to accept the vaccine for their child and preferences for how the vaccine should be administered (in combination with the MMR vaccine [MMRV], on the same day as the MMR vaccine but as a separate injection [MMR + V], on a separate additional visit).

RESULTS

74.0% of parents (95% CI 70.2% to 77.5%) were extremely/somewhat likely to accept a varicella vaccine for their child if one became available, 18.3% (95% CI 15.3% to 21.8%) were extremely/somewhat unlikely to accept it and 7.7% (95% CI 5.7% to 10.2%) were neither likely nor unlikely. Reasons provided by parents likely to accept the vaccine included protection from complications of chickenpox, trust in the vaccine/healthcare professionals, and wanting their child to avoid their personal experience of chickenpox. Reasons provided by parents who were unlikely included chickenpox not being a serious illness, concern about side effects, and believing it is preferable to catch chickenpox as a child rather than as an adult. A combined MMRV vaccination or additional visit to the surgery were preferred over an additional injection at the same visit.

CONCLUSIONS

Most parents would accept a varicella vaccination. These findings highlight parents' preferences for varicella vaccine administration, information needed to inform vaccine policy and practice and development of a communication strategy.

Systematic review of economic evaluations of varicella vaccination programmes

OBJECTIVES

This study carried out a systematic literature review of economic evaluations of varicella vaccination programmes from the earliest publication to the present day, including programmes in the workplace and in special risk groups as well as universal childhood vaccination and catch up programmes.

METHODS

Articles published from 1985 until 2022 were sourced from PubMed/Medline, Embase, Web of Science, NHSEED and Econlit. Eligible economic evaluations, which included posters and conference abstracts, were identified by two reviewers who scrutinised each other's selections at both title and abstract and full report stages. The studies are described in terms of their methodological characteristics. Their results are aggregated by type of vaccination programme and the nature of the economic outcome.

RESULTS

A total of 2575 articles were identified of which 79 qualified as economic evaluations. A total of 55 studies focused on universal childhood vaccination, 10 on the workplace and 14 on high risk groups. Twenty-seven studies reported estimates of incremental cost per quality-adjusted life year (QALY) gained, 16 reported benefit-cost ratios, 20 reported cost-effectiveness outcomes in terms of incremental cost per event or life saved and 16 reported cost-cost offset results. Most studies of universal childhood vaccination reported an increase in overall costs to health services, but often a reduction in cost from a societal perspective.

CONCLUSIONS

The evidence surrounding the cost-effectiveness of varicella vaccination programmes remains sparse with contrasting conclusions in some areas. Future research should particularly aim to encompass the impact of universal childhood vaccination programmes on herpes zoster among adults.

Seasonal transmission dynamics of varicella in Japan: The role of temperature and school holidays

In Japan, major and minor bimodal seasonal patterns of varicella have been observed. To investigate the underlying mechanisms of seasonality, we evaluated the effects of the school term and temperature on the incidence of varicella in Japan. We analyzed epidemiological, demographic and climate datasets of seven prefectures in Japan. We fitted a generalized linear model to the number of varicella notifications from 2000 to 2009 and quantified the transmission rates as well as the force of infection, by prefecture. To evaluate the effect of annual variation in temperature on the rate of transmission, we assumed a threshold temperature value. In northern Japan, which has large annual temperature variations, a bimodal pattern in the epidemic curve was observed, reflecting the large deviation in average weekly temperature from the threshold value. This bimodal pattern was diminished with southward prefectures, gradually shifting to a unimodal pattern in the epidemic curve, with little temperature deviation from the threshold. The transmission rate and force of infection, considering the school term and temperature deviation from the threshold, exhibited similar seasonal patterns, with a bimodal pattern in the north and a unimodal pattern in the south. Our findings suggest the existence of preferable temperatures for varicella transmission and an interactive effect of the school term and temperature. Investigating the potential impact of temperature elevation that could reshape the epidemic pattern of varicella to become unimodal, even in the northern part of Japan, is required.

Chickenpox and multiple sclerosis: A Mendelian randomization study

Observational studies have suggested a suspected association between varicella-zoster virus (VZV) infection and multiple sclerosis (MS), but the connection has remained unclear. The aim of the present study is to evaluate the causal relationship between chickenpox which is caused by VZV infection and MS. We performed a two-sample Mendelian randomization analysis to investigate the association of chickenpox with MS using summary statistics from genome-wide association studies (GWAS). The GWAS summary statistics data for chickenpox was from the 23andMe cohort including 107 769 cases and 15 982 controls. A large summary of statistical data from the International Multiple Sclerosis Genetics Consortium (IMSGC) was used as the outcome GWAS data set, including 14 802 MS cases and 26 703 controls. We found evidence of a significant association between genetically predicted chickenpox and risk of MS (odds ratio [OR] = 35.27, 95% confidence interval [CI] = 22.97-54.17, p = 1.46E-59). Our findings provided evidence indicating a causal effect of chickenpox on MS. Further elucidations of this association and underlying mechanisms are needed for identifying feasible interventions to promote MS prevention.

Effects of meteorological factors on the incidence of varicella in Lu'an, Eastern China, 2015-2020

Varicella (chickenpox) is a serious public health problem in China, with the most reported cases among childhood vaccine-preventable infectious diseases, and its reported incidence has increased over 20-fold since 2005. Few previous studies have explored the association of multiple meteorological factors with varicella and considered the potential confounding effects of air pollutants. It is the first study to investigate and analyze the effects of multiple meteorological factors on varicella incidence, controlling for the confounding effects of various air pollutants. Daily meteorological and air pollution data and varicella cases were collected from January 1, 2015, to December 31, 2020, in Lu'an, Eastern China. A combination of the quasi-Poisson generalized additive model (GAM) and distributed lag nonlinear model (DLNM) was used to evaluate the meteorological factor-lag-varicella relationship, and the risk of varicella in extreme meteorological conditions. The maximum single-day lag effects of varicella were 1.288 (95%CI, 1.201-1.381, lag 16 day), 1.475 (95%CI, 1.152-1.889, lag 0 day), 1.307 (95%CI, 1.196-1.427, lag 16 day), 1.271 (95%CI, 0.981-1.647, lag 4 day), and 1.266 (95%CI, 1.162-1.378, lag 21 day), when mean temperature, diurnal temperature range (DTR), mean air pressure, wind speed, and sunshine hours were -5.8°C, 13.5°C, 1035.5 hPa, 6 m/s, and 0 h, respectively. At the maximum lag period, the overall effects of mean temperature and pressure on varicella showed W-shaped curves, peaked at 17.5°C (RR=2.085, 95%CI: 1.480-2.937) and 1035.5 hPa (RR=5.481, 95%CI: 1.813-16.577), while DTR showed an M-shaped curve and peaked at 4.4°C (RR=6.131, 95%CI: 1.120-33.570). Sunshine hours were positively correlated with varicella cases at the lag of 0-8 days and 0-9 days when sunshine duration exceeded 10 h. Furthermore, the lag effects of extreme meteorological factors on varicella cases were statistically significant, except for the extremely high wind speed. We found that mean temperature, mean air pressure, DTR, and sunshine hours had significant nonlinear effects on varicella incidence, which may be important predictors of varicella early warning.

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.

Evaluating the impact of universal varicella vaccination among preschool-aged children in Qingdao, China: An interrupted time-series analysis

Varicella is a contagious disease of children. Qingdao administrated free one-dose and free two-dose universal varicella vaccination schedules in 2013 and 2016 for preschool children. The effectiveness of the vaccination was analyzed in this study. Monthly varicella incidence data of 1-6 years old children during 2007-2020 were obtained from the Qingdao Infectious Disease Reporting Information Management System. We applied Interrupted time series and segmented regression analyses to assess changes in varicella incidence at the beginning of each month and average monthly changes during the vaccination. The vaccination was associated with a reduction of 32.7% in varicella morbidity on average during the 8-year intervention, there is a statistically significant difference between the voluntary period and free vaccination period (χ² = 290.80,P < 0.001). Immediately after the free one-dose vaccination implementation in 2013 and free two-dose vaccination implementation in 2016, varicella incidence decreased by 0.135 cases per 100 000 population (P < 0.001) and increased by 1.189 cases per 100 000 population (P = 0.039), respectively, the results were statistically significant. There were significant declining trends in varicella incidence after free vaccination: 0.135(P < 0.001) and 0.055 (P = 0.025) per month in 2013.7-2016.6 and 2016.7-2020.12, respectively. This study shows a further decaying trend of varicella incidence based on the impact of free two-dose vaccination. It is necessary to prolong free two-dose universal varicella vaccination to strengthen the immune barrier of preschool children sequentially.

The health and economic impact of switching vaccines in universal varicella vaccination programs using a dynamic transmission model: An Israel case study

Currently available health economic models for varicella infection are designed to inform the cost-effectiveness of universal varicella vaccination (UVV) compared with no vaccination. However, in countries with an existing UVV program, these models cannot be used to evaluate whether to continue with the current varicella vaccine or to switch to an alternative vaccine. We developed a dynamic transmission model that incorporates the historical vaccination program to project the health and economic impact of changing vaccination strategies. We applied the model to Israel, which initiated UVV in 2008 with a quadrivalent vaccine, MMRV-GSK, and switched to MMRV-MSD in 2016. The model was calibrated to pre-vaccination incidence data before projecting the impact of the historical and future alternative vaccination strategies on the clinical burden of varicella. Total costs and QALYs lost due to varicella infections were projected to compare continuing with MMRV-MSD versus switching to MMRV-GSK in 2022. Over a 50-year time horizon, continuing with MMRV-MSD reduced varicella incidence further by 64%, reaching 35 cases per 100,000 population by 2072, versus a 136% increase in incidence with MMRV-GSK. Continuing with MMRV-MSD reduced cumulative hospitalization and outpatient cases by 48% and 58% (vs. increase of 137% and 91% with MMRV-GSK), respectively. Continuing with MMRV-MSD resulted in 139 fewer QALYs lost with total cost savings of 3% compared with switching to MMRV-GSK, from the societal perspective. In Israel, maintaining the UVV strategy with MMRV-MSD versus switching to MMRV-GSK is projected to further reduce the burden of varicella and cost less from the societal perspective.

National and provincial burden of varicella disease and cost-effectiveness of childhood varicella vaccination in China from 2019 to 2049: a modelling analysis

Background

In China, varicella is the third most frequently reported vaccine-preventable infectious disease after tuberculosis and influenza, and imposes a heavy burden on families and society. To inform future immunization policy, we investigated disease burden of varicella in China and explored cost-effectiveness of different varicella vaccination strategies at national and provincial levels.

Methods

A dynamic transmission model was developed to assess disease burden of varicella and the impact of varicella vaccination in China. A cost-effectiveness analysis of three alternative vaccination strategies in China's National Immunization Program (NIP) compared with no vaccination was conducted. Scenario analyses and sensitivity analyses were performed to check the robustness of the results.

Findings

It was estimated that 3.35 million new varicella cases occurred in 2019, more than three times of 982 thousand cases officially reported from National Notifiable Infectious Disease Surveillance System (NNIDSS). The under-reported rate was approximately 71%. The economic analysis revealed that from the societal perspective, the incremental cost-effectiveness ratio (ICER) for one dose of varicella vaccination in NIP was US$ 2357 per QALY at the national level and it was cost-effective in 22 of 31 provinces. The ICER for one dose varicella vaccination plus a mass catch-up for unvaccinated children aged 2-11 years old would be US$ -5260 per QALY, cost-saving at the national level. The one dose plus mass catch-up NIP strategy was also cost-saving in 24 of the 31 provinces.

Interpretation

Varicella incident cases were substantially under-reported in China. Varicella vaccination in the NIP could significantly contribute to reducing the burden of varicella disease. From the societal perspective, including varicella vaccination into China's NIP was highly cost-effective at the national level and in most provinces.

Funding

Bill & Melinda Gates Foundation.

Monitoring Varicella Vaccine Impact on Varicella Incidence in the United States: Surveillance Challenges and Changing Epidemiology, 1995-2019

Surveillance is critical for monitoring vaccine impact. Varicella surveillance challenges predated varicella vaccine US licensure in 1995. Several interim steps were needed before case-based surveillance could be established in most states, and both active and passive surveillance was needed to document the vaccination program's impact on varicella incidence. By the end of the 1-dose program in 2005, incidence had declined 90% in the active surveillance areas, with significant declines occurring in all age groups within 5 years of program implementation. Additional declines occurred during the 2-dose program leading to >97% decline in incidence over the 25 years of program implementation through 2019, based on data from 4 states with continuous passive reporting. Surveillance showed that declines were highest among children and adolescents covered by the routine vaccination recommendations but occurred in all age groups. Although surveillance systems changed and were adapted to reflect evolving epidemiology, data consistently demonstrated decreasing varicella incidence following the vaccination program implementation. The vaccination program dramatically decreased virus circulation and increased community protection. Continued and improved varicella surveillance is needed to accurately monitor disease epidemiology and further guide prevention efforts.

Changing Epidemiology of Varicella Outbreaks in the United States During the Varicella Vaccination Program, 1995-2019

We describe the changing epidemiology of varicella outbreaks informed by past and current active and passive surveillance in the United States by reviewing data published during 1995-2015 and analyzing new data from 2016 to 2019. Varicella outbreaks were defined as ≥5 varicella cases within 1 setting and ≥1 incubation period. During the 1-dose varicella vaccination program (1995‒2006), the number of varicella outbreaks declined by 80% (2003-2006 vs 1995-1998) in 1 active surveillance area where vaccination coverage reached 90.5% in 2006. During the 2-dose program, in 7 states with consistent reporting to the Centers for Disease Control and Prevention, the number of outbreaks declined by 82% (2016-2019 vs 2005-2006). Over the entire program (1995-2019), outbreak size and duration declined from a median of 15 cases/outbreak and 45 days duration to 7 cases and 30 days duration. The proportion of outbreaks with <10 cases increased from 28% to 73%. During 2016‒2019, most (79%) outbreak cases occurred among unvaccinated or partially vaccinated persons eligible for second-dose vaccination, highlighting the potential for further varicella control.

The Effectiveness of Varicella Vaccine: 25 Years of Postlicensure Experience in the United States

We summarize studies of varicella vaccine's effectiveness for prevention of varicella and lessons learned during the first 25 years of the varicella vaccination program in the United States. One dose of varicella vaccine provided moderate protection (82%-85%) against varicella of any severity and high protection (100%) against severe varicella, with some waning of protection over time. The 1-dose program (1995-2006) had a substantial impact on the incidence both of varicella and of severe outcomes (71%-90% decrease) although it did not prevent low-level community transmission and some outbreaks continued to occur in highly vaccinated populations. Two doses of varicella vaccine improved the vaccine's effectiveness by at least 10% against varicella of any severity, with further declines in the incidence both of varicella and of severe outcomes as well as in both number and size of outbreaks. There is no evidence for waning of the effectiveness of 2 doses of the vaccine.

Decline in Severe Varicella Disease During the United States Varicella Vaccination Program: Hospitalizations and Deaths, 1990-2019

To describe the impact of the US varicella vaccination program on severe varicella outcomes, we analyzed varicella hospitalizations using the National Inpatient Sample 1993-2019 and varicella deaths using the National Center for Health Statistics data 1990-2019. Over 25 years of vaccination program (1995-2019), varicella hospitalizations, and deaths declined 94% and 97%, respectively, among persons aged <50 years. Most of the decline (∼90%) occurred during the 1-dose period (through 2006/2007) by attaining and maintaining high vaccination coverage; additional declines occurred during the 2-dose period, especially in the age groups covered by the 2-dose recommendation. The greatest decline for both hospitalizations and deaths (97% and >99%, respectively) was among persons aged <20 years, born during the varicella vaccination program. In the <20 age group, varicella hospitalization has become a rare event, and varicella deaths have been practically eliminated in the United States. A total of >10 500 varicella hospitalizations and 100 varicella deaths are now prevented annually in the United States as a direct result of vaccination and reduction in varicella-zoster virus circulation.

Clinical Manifestations of Varicella: Disease Is Largely Forgotten, but It's Not Gone

After 25 years of varicella vaccination in the United States, classic varicella and its complications have become an uncommon occurrence. The clinical manifestation of varicella among vaccinated persons is usually modified, with fewer skin lesions, mostly maculopapular, and milder presentation. However, the potential for severe manifestations from varicella still exists among both vaccinated and unvaccinated persons, and thus healthcare providers should keep varicella in the differential diagnosis of a maculopapular or vesicular rash. The prompt recognition and diagnosis of varicella is important because when confirmed, clinical and public health measures need to be taken swiftly.

Identifying optimal vaccination scenarios to reduce varicella zoster virus transmission and reactivation

BACKGROUND

Varicella zoster virus (VZV) is one of the eight known human herpesviruses. Initial VZV infection results in chickenpox, while viral reactivation following a period of latency manifests as shingles. Separate vaccines exist to protect against both initial infection and subsequent reactivation. Controversy regarding chickenpox vaccination is contentious with most countries not including the vaccine in their childhood immunization schedule due to the hypothesized negative impact on immune-boosting, where VZV reactivation is suppressed through exogenous boosting of VZV antibodies from exposure to natural chickenpox infections.

METHODS

Population-level chickenpox and shingles notifications from Thailand, a country that does not vaccinate against either disease, were previously fitted with mathematical models to estimate rates of VZV transmission and reactivation. Here, multiple chickenpox and shingles vaccination scenarios were simulated and compared to a model lacking any vaccination to analyze the long-term impacts of VZV vaccination.

RESULTS

As expected, simulations suggested that an introduction of the chickenpox vaccine, at any coverage level, would reduce chickenpox incidence. However, chickenpox vaccine coverage levels above 35% would increase shingles incidence under realistic estimates of shingles coverage with the current length of protective immunity from the vaccine. A trade-off between chickenpox and shingles vaccination coverage was discovered, where mid-level chickenpox coverage levels were identified as the optimal target to minimize total zoster burden. Only in scenarios where shingles vaccine provided lifelong immunity or coverage exceeded current levels could large reductions in both chickenpox and shingles be achieved.

CONCLUSIONS

The complicated nature of VZV makes it impossible to select a single vaccination scenario as universal policy. Strategies focused on reducing both chickenpox and shingles incidence, but prioritizing the latter should maximize efforts towards shingles vaccination, while slowly incorporating chickenpox vaccination. Alternatively, countries may wish to minimize VZV complications of both chickenpox and shingles, which would lead to maximizing vaccine coverage levels across both diseases. Balancing the consequences of vaccination to overall health impacts, including understanding the impact of an altered mean age of infection for both chickenpox and shingles, would need to be considered prior to any vaccine introduction.

A case of chickenpox with multiple bacterial complications requiring surgical treatment

Chickenpox is a controlled infection, even a single vaccination effectively prevents the development of severe forms (up to 98%).

Purpose — to demonstrate a case of severe chicken pox in a child aged 3.8 years with secondary infection of the skin of the right subscapular region and subcutaneous fat (phlegmon of the trunk) of streptococcal etiology.

The diagnosis of varicella was confirmed by the detection of Varicella-Zoster virus DNA by PCR from the skin. Surgical treatment was performed — opening and drainage of phlegmon, purulent-serous discharge was obtained, sowing was performed, Streptococcus pyogenes was isolated.

The child received antibiotic therapy — cefepime sulbactam, amikacin, acyclovir, infusion therapy, local treatment.

Conclusions. The given clinical case demonstrates the development of a severe bacterial complication of chicken pox, which required surgical treatment and substantiates the need for vaccination against chicken pox and its possible complications.

Relative efficacy of varicella vaccines: network meta-analysis of randomized controlled trials

OBJECTIVE

Although varicella vaccination is highly effective, no head-to-head randomized controlled trials (RCTs) have compared the efficacy of different vaccine formulations. This study assessed the relative efficacy of different varicella vaccines using network meta-analysis (NMA).

METHODS

We estimated the relative efficacies of varicella vaccines and dosing regimens from RCTs using Bayesian NMA. Modeling-based time-series NMA (MBNMA) was performed, accounting for differences in time since vaccination, to extrapolate long-term vaccine efficacy (VE).

RESULTS

Eight RCTs were included based on systematic review of biomedical databases. Efficacy data were reported for four varicella-containing vaccines: Varivax (V-MSD, one and two dose), Varilrix (V-GSK, one dose), Priorix-Tetra (MMRV-GSK, one dose), and Sinovac (V-Sinovac, one dose). All varicella vaccines were effective versus no vaccination. Two-dose V-MSD (98.29%, 95% credible interval [CrI] 96.08-99.23) showed significantly higher VE versus all one-dose varicella-containing vaccines, but no significant difference versus two-dose MMRV-GSK (95.19%, 95% CrI 90.3-97.63). Two-dose MMRV-GSK showed higher VE than one-dose V-GSK (66.47%; 95% CrI 43.02-79.43), but no significant differences in VE versus one-dose V-MSD or one-dose V-Sinovac. In one-dose comparisons, V-MSD showed significantly higher VE (93.09%, 95% CrI 89.13-95.96) than V-GSK, but no significant difference versus V-Sinovac (89.22%; 95% CrI 67.1-96.5). MBNMA indicated that protection against varicella was sustained without waning over the 10 year follow-up.

CONCLUSIONS

Our study reported higher VE for two-dose V-MSD and MMRV-GSK. Among one-dose formulations, one-dose V-MSD was more efficacious than one-dose V-GSK. Policymakers should take into consideration differences in VE when implementing one- versus two-dose strategies in universal vaccination programs.

The Long-Term Clinical and Economic Impact of Universal Varicella Vaccination in Slovenia

Background: Despite the substantial burden of varicella infection, Slovenia does not currently have a universal varicella vaccination (UVV) program. We modeled the long-term clinical and economic impact of implementing 2-dose UVV strategies compared with no vaccination in Slovenia. Methods: A previously published dynamic transmission model was adapted to the demographics, varicella seroprevalence, herpes zoster incidence, and contact patterns in Slovenia. Six 2-dose UVV strategies, vs no vaccination, were considered over a 50-year period, including monovalent vaccination (Varivax^® [V-MSD] or Varilrix^® [V-GSK]) at ages 12 and 24 months, or monovalent vaccination at 15 months followed by monovalent or quadrivalent vaccination (ProQuad^® [MMRV-MSD] or Priorix- Tetra^® [MMRV-GSK]) at 5.5 years. Costs, quality-adjusted life-years, and incremental cost-effectiveness ratios vs no vaccination were calculated to assess the economic impact of each strategy from payer and societal perspectives. Results: The incidence of varicella infection was estimated as 1228 per 100 000 population in the absence of UVV. Over 50 years, depending on vaccination strategy, UVV reduced varicella cases by 77% to 85% and was associated with substantial reductions in varicella deaths (39%-44%), outpatient cases (74%-82%), and hospitalizations (74%-82%). The greatest reductions were predicted with V-MSD (15 months/5.5 years) and V MSD/MMRV-MSD (15 months/5.5 years). Discussion: All 2-dose UVV strategies were cost-effective compared with no vaccination from payer and societal perspectives, with V-MSD (15 months/5.5 years) being the most favorable from both perspectives. Conclusion: Policymakers should consider implementing UVV to reduce the burden of varicella disease in Slovenia.

Post-exposure prophylaxis to prevent varicella in immunocompromised children

Background

Varicella-zoster virus (VZV) infection can cause life-threatening events in immunocompromised patients. Post-exposure prophylaxis (PEP) is required to prevent secondary VZV infection. Limited evidence is available for the use of acyclovir (ACV)/valacyclovir (VCV) as PEP.

Methods

Herein, we retrospectively analyzed immunocompromised paediatric patients with significant exposure to VZV. Patients administered PEP were categorized into four groups: 1) ACV/VCV group; 2) intravenous immunoglobulin (IVIG) group; 3) ACV/VCV/IVIG group; 4) vaccine group.

Results

Among 69 exposure events, 107 patients were administered PEP (91, ACV/VCV; 16, ACV/VCV/IVIG) and 10 patients did not receive PEP (non-PEP group). The index case was diagnosed based on clinical symptoms in 55 cases (79.7%). Fourteen cases (20.3%) were confirmed using direct virological diagnostic procedures. In the PEP group, only 2 patients (2.2%) developed secondary VZV infections. Additionally, 2 patients in the non-PEP group (20.0%) developed secondary VZV infection. The incidence of secondary VZV infection was significantly lower in the PEP group than in the non-PEP group (P=0.036). Among patients administered PEP, no antiviral drug-induced side effects were detected.

Conclusions

Antiviral agents administered as PEP are effective and safe for preventing VZV infections in immunocompromised patients. Rapid virological diagnosis of index cases might allow efficient administration of PEP after significant exposure to VZV infection.

Vaccine Coverage and Effectiveness in a School-Based Varicella Outbreak in Jinan Prefecture, Shandong Province

Background: Licheng District of Jinan Prefecture reported a school-based varicella outbreak. We conducted an investigation to analyze the epidemiology and scope of the outbreak, determine varicella vaccine coverage on the school campus, and estimate varicella vaccine effectiveness (VE). Methods: In the epidemiological investigation, we determined the attack rate, the clinical manifestations of varicella cases, and histories of prior varicella disease and varicella vaccination. We tested students for presence of serum IgM antibodies, and we attempted to isolate the varicella virus from vesicular fluid samples. We used chi-square to compare incidences between classes and floors. VE was estimated using a retrospective cohort study. Results: There were 13 varicella cases in the outbreak. All were among fourth grade students - twelve in Class 7 and one in Class 6. The attack rate in the two classrooms was 14.3% (13/91). Clinical symptoms were rash (100%) and fever (46.15%). All cases were reported within one average incubation period, and the epidemic curve suggested common exposure. Six of the 13 cases previously received one dose of varicella vaccine with a median time between vaccination and infection of 9 years; the other seven cases had not been vaccinated. Varicella vaccine coverage with one or more doses was 81.31%; 2-dose coverage was 38.15%. The median age of receipt of dose 1 was 1.18 years, and median age for receiving dose 2 was 5.12 years. One-dose varicella VE was 73.2% (95% confidence interval: 37.0%, 88.6%), and two-dose VE was 100%. Conclusions: Varicella vaccine coverage has been gradually increasing in recent years, as ≥1-dose and 2-dose coverage rates are higher in younger children than older children. High one-dose vaccination coverage limited the outbreak scope and led to the breakthrough cases being mild. Mild cases were difficult to detect in a timely manner. Varicella vaccine was highly effective, with 1-dose VE of 73% nine years after vaccination and 2-dose VE of 100%. We strongly recommended that all school students receive two doses of varicella vaccine.

Comparison of performance of varicella vaccines via infectious disease modeling

BACKGROUND

Population-level infectious disease models for varicella require vaccine parameters, namely 'take' and 'duration of protection' (defined here as vaccine performance), to quantify the impact of vaccination. Current published models for varicella use vaccine parameters derived from various methodologies which does not allow for the direct comparison of different vaccines.

METHODS

We estimated take and duration of protection using deterministic compartmental models to simulate clinical trials of one- or two-dose varicella vaccination using Varivax® (V-MSD) and Varilrix® (V-GSK). We fit different models to clinical trial data on breakthrough infections and evaluated their respective goodness-of-fit using the Akaike Information Criterion (AIC).

RESULTS

Based upon the clinical trial data, we estimated that 90.3% (95% CI: 87.8-92.9%) of the cohort gained permanent protection from breakthrough varicella after the first dose of V-MSD compared to 61.7% (95% CI: 58.2-65.3%) with the first dose of V-GSK. We further estimated that a total of 97.0% (95% CI: 95.2-98.8%) and 93.8% (95% CI: 92.2-95.4%) of the cohort were permanently protected after two-doses of V-MSD and V-GSK, respectively. According to the AIC, our new model (V-MSD AIC = 92.7; V-GSK AIC = 170.3) provided a better fit than an existing model (V-MSD AIC = 108.9; V-GSK AIC = 216.1).

CONCLUSIONS

The model developed fits the long-term clinical trial data on breakthrough infections for both V-MSD and V-GSK, thus, allowing for the direct comparison of vaccine performance. We estimated that a single dose of V-MSD was more likely to provide permanent protection than a single dose of V-GSK, while the protection offered by two doses was similar for both vaccines.

Estimation of single-dose varicella vaccine effectiveness in South Korea using mathematical modeling

In South Korea, despite the implementation of a universal single-dose vaccination program for children aged 12–15 months in 2005, the varicella incidence rate remains significant. Prior case-control studies have reported that currently used varicella vaccines are extremely inefficacious. We estimated vaccine effectiveness (VE) by fitting a dynamic transmission model to age-specific varicella incidence data from 2007 to 2015 and available vaccine coverage data. The initial vaccine efficacy and primary failure rates were estimated to be 61.1% and 38.9%, respectively. The average duration of protection was 21.4 years. The mean VE [(1-relative risk) %] for the simulated data of 2004–2014 birth cohorts decreased from 59.8% to 50.7% over 9 years. This mathematical modeling study demonstrated that the single-dose vaccine exhibits moderate effectiveness, and a high proportion of primary failure could be a main cause of breakthrough infections. Therefore, a two-dose vaccination strategy should be considered.

Impact of universal varicella vaccination on the use and cost of antibiotics and antivirals for varicella management in the United States

Background

Our objective was to estimate the impact of universal varicella vaccination (UVV) on the use and costs of antibiotics and antivirals for the management of varicella among children in the United States (US).

Methods

A decision tree model of varicella vaccination, infections and treatment decisions was developed. Results were extrapolated to the 2017 population of 73.5 million US children. Model parameters were populated from published sources. Treatment decisions were derived from a survey of health care professionals’ recommendations. The base case modelled current vaccination coverage rates in the US with additional scenarios analyses conducted for 0%, 20%, and 80% coverage and did not account for herd immunity benefits.

Results

Our model estimated that 551,434 varicella cases occurred annually among children ≤ 18 years in 2017. Antivirals or antibiotics were prescribed in 23.9% of cases, with unvaccinated children receiving the majority for base case. The annual cost for varicella antiviral and antibiotic treatment was approximately $14 million ($26 per case), with cases with no complications accounting for $12 million. Compared with the no vaccination scenario, the current vaccination rates resulted in savings of $181 million (94.7%) for antivirals and $78 million (95.0%) for antibiotics annually. Scenario analyses showed that higher vaccination coverage (from 0% to 80%) resulted in reduced annual expenditures for antivirals (from $191 million to $41 million), and antibiotics ($82 million to $17 million).

Conclusions

UVV was associated with significant reductions in the use of antibiotics and antivirals and their associated costs in the US. Higher vaccination coverage was associated with lower use and costs of antibiotics and antivirals for varicella management.