The effect of funded varicella immunization programs on varicella-related hospitalizations in IMPACT centers, Canada, 2000-2008

Global Prevalence of Varicella-Associated Complications: A Systematic Review and Meta-Analysis

INTRODUCTION

Varicella (chickenpox) is an infectious disease caused by the varicella zoster virus affecting children, adolescents, and adults. Varicella symptoms are usually self-limiting; however, different complications with widespread and systemic manifestations can occur. This systematic literature review aims to explore and quantify varicella-associated complication rates.

METHODS

Two databases (Embase and MEDLINE), congress abstracts, and reference lists of systematic reviews were screened to identify evidence on varicella complications. Complications were identified and grouped into 14 clinically relevant categories. Proportional meta-analyses were conducted using a random-effects model and tests for heterogeneity and publication bias were performed. Subgroup, sensitivity, and meta-regression analyses were also conducted. A total of 78 studies, spanning 30 countries, were included in the meta-analysis.

RESULTS

Pooled prevalence was highest in severe varicella (22.42%; 95% confidence interval [CI] 10.13-37.77), skin-related complications (20.12%; 95% CI 15.48-25.20), and infection-related complications (10.03%; 95% CI 7.47-12.90). Cardiovascular (0.55%; 95% CI 0.08-1.33), genitourinary (1.17%; 95% CI 0.55-1.99), and musculoskeletal (1.54%; 95% CI 1.06-2.11) complications had the lowest pooled prevalence. The remaining complication categories ranged between 1% and 10%. Subgroup analysis showed that complications were more prevalent in children versus adults and in hospitalized patients versus outpatients. Meta-regression analysis found that no ecological level covariates were accurate predictors for the overall prevalence of varicella-associated complications. There was substantial heterogeneity and publication bias across all meta-analyses.

CONCLUSION

Results suggest that different types of varicella-associated complications could be frequent, impacting quality of life, and healthcare resource utilisation and budgets. These findings are crucial to raise awareness of the health and economic burden of varicella disease.

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.

Has Clinical and Epidemiological Varicella Burden Changed over Time in Children? Overview on Hospitalizations, Comorbidities and Costs from 2010 to 2017 in Italy

According to WHO estimates, varicella disease is responsible of a worldwide significant burden in terms of hospitalizations, complications, and deaths, with more than 90% of cases under 12 years old. This study aims at evaluating the clinical, epidemiological, and economic burden of varicella in Ligurian children, about comorbidities, organizational variables, and vaccination coverages from 2010 to 2017, in terms of Emergency Department accesses and hospitalizations. The overall hospitalization rate was 179.76 (per 100,000 inhab.), with a gradual but significant decline since 2015, when universal varicella vaccination was introduced in Liguria (p < 0.0001). The risk of being hospitalized for complicated varicella in subjects with at least one comorbidity was significantly higher than in subjects without comorbidities (p = 0.0016). The economic analysis showed higher costs in subjects with complicated varicella who were 0-3 years old. This age group showed higher costs also considering extra-hospital costs for both outpatient procedures and pharmaceutical costs (p < 0.0001). The results confirm the relevant burden of varicella, especially in the 0-3 age group and in children with comorbidities. Thus, vaccination with the achievement of adequate vaccination coverages is confirmed to be a necessary control strategy to reduce hospitalizations and associated complications with important economic benefits.

Clinical and economic impact of universal varicella vaccination in Norway: A modeling study

BACKGROUND

Norway has not implemented universal varicella vaccination, despite the considerable clinical and economic burden of varicella disease.

METHODS

An existing dynamic transmission model of varicella infection was calibrated to age-specific seroprevalence rates in Norway. Six two-dose vaccination strategies were considered, consisting of combinations of two formulations each of a monovalent varicella vaccine (Varivax® or Varilrix®) and a quadrivalent vaccine against measles-mumps-rubella-varicella (ProQuad® or PriorixTetra®), with the first dose given with a monovalent vaccine at age 15 months, and the second dose with either a monovalent or quadrivalent vaccine at either 18 months, 7 or 11 years. Costs were considered from the perspectives of both the health care system and society. Quality-adjusted life-years saved and incremental cost-effectiveness ratios relative to no vaccination were calculated. A one-way sensitivity analysis was conducted to assess the impact of vaccine efficacy, price, the costs of a lost workday and of inpatient and outpatient care, vaccination coverage, and discount rate.

RESULTS

In the absence of varicella vaccination, the annual incidence of natural varicella is estimated to be 1,359 per 100,000 population, and the cumulative numbers of varicella outpatient cases, hospitalizations, and deaths over 50 years are projected to be 1.81 million, 10,161, and 61, respectively. Universal varicella vaccination is projected to reduce the natural varicella incidence rate to 48-59 per 100,000 population, depending on the vaccination strategy, and to reduce varicella outpatient cases, hospitalizations, and deaths by 75-85%, 67-79%, and 75-79%, respectively. All strategies were cost-saving, with the most cost-saving as two doses of Varivax® at 15 months and 7 years (payer perspective) and two doses of Varivax® at 15 months and 18 months (societal perspective).

CONCLUSIONS

All modeled two-dose varicella vaccination strategies are projected to lead to substantial reductions in varicella disease and to be cost saving compared to no vaccination in Norway.

Association between Antiviral Prophylaxis and Cytomegalovirus and Epstein-Barr Virus DNAemia in Pediatric Recipients of Allogeneic Hematopoietic Stem Cell Transplant

Background: Epstein–Barr virus (EBV) and cytomegalovirus (CMV) infections can have serious consequences during the period of aplasia and lymphopenia following hematopoietic stem cell transplantation (HSCT). Large pediatric cohort studies examining the effect of antiviral prophylaxis against these viruses are scarce. The present study aimed to analyse the potential effect of antiviral prophylaxis (acyclovir and famciclovir) on active post-transplant EBV and CMV infection in a pediatric cohort of allogeneic HSCT recipients. Methods: We used data from the TREASuRE cohort, consisting of 156 patients who had a first allogeneic HSCT, enrolled in four pediatric centers in Canada between July 2013 and March 2017. Follow-up was performed from the time of transplant up to 100 days post-transplant. Adjusted hazard ratio (HR) with 95% confidence intervals (CI) for the association between antiviral prophylaxis with acyclovir and/or famciclovir and EBV and CMV DNAemia was estimated using multivariate Cox regression models. Results: The post-transplant cumulative incidence of EBV and CMV DNAemia at 100 days of follow-up were, respectively, 34.5% (95% CI: 27.6–42.6) and 19.9% (95% CI: 14.5–27.1). For acyclovir, the adjusted hazard ratio (HR) for CMV and EBV DNAemia was 0.55 (95% CI: 0.24–1.26) and 1.41 (95% CI: 0.63–3.14), respectively. For famciclovir, the adjusted HR were 0.82 (95% CI: 0.30–2.29) and 0.79 (95% CI: 0.36–1.72) for CMV and EBV DNAemia, respectively. Conclusion: The antivirals famciclovir and acyclovir did not reduce the risk of post-transplant CMV and EBV DNAemia among HSCT recipients in our pediatric population.

Active surveillance of acute paediatric hospitalisations demonstrates the impact of vaccination programmes and informs vaccine policy in Canada and Australia

Sentinel surveillance of acute hospitalisations in response to infectious disease emergencies such as the 2009 influenza A(H1N1)pdm09 pandemic is well described, but recognition of its potential to supplement routine public health surveillance and provide scalability for emergency responses has been limited. We summarise the achievements of two national paediatric hospital surveillance networks relevant to vaccine programmes and emerging infectious diseases in Canada (Canadian Immunization Monitoring Program Active; IMPACT from 1991) and Australia (Paediatric Active Enhanced Disease Surveillance; PAEDS from 2007) and discuss opportunities and challenges in applying their model to other contexts. Both networks were established to enhance capacity to measure vaccine preventable disease burden, vaccine programme impact, and safety, with their scope occasionally being increased with emerging infectious diseases’ surveillance. Their active surveillance has increased data accuracy and utility for syndromic conditions (e.g. encephalitis), pathogen-specific diseases (e.g. pertussis, rotavirus, influenza), and adverse events following immunisation (e.g. febrile seizure), enabled correlation of biological specimens with clinical context and supported responses to emerging infections (e.g. pandemic influenza, parechovirus, COVID-19). The demonstrated long-term value of continuous, rather than incident-related, operation of these networks in strengthening routine surveillance, bridging research gaps, and providing scalable public health response, supports their applicability to other countries.

Congenital viral infections in England over five decades: a population-based observational study

BACKGROUND

Congenital viral infections cause substantial long-term morbidity but population-based data about diagnosis rates are scarce. The aim of this study was to assess the long-term trends in congenital viral infections in England and to report on how the rates of these infections might have changed with improved methods for detection, the introduction of the two-dose measles-mumps-rubella (MMR) vaccine in 1996, and the implementation of the Newborn Hearing Screening Programme (NHSP) in 2006.

METHODS

For this population-based, observational cohort study, we used national and regional hospitalisation data from 1968 to 2016 in England (Hospital In-Patient Enquiry, Hospital Episode Statistics, and Oxford Record Linkage Study) to calculate annual rates of hospital discharges coded with-and individuals aged younger than 1 month diagnosed with-congenital cytomegalovirus, herpes simplex virus (HSV), varicella zoster virus (VZV), and rubella. We investigated associations of congenital cytomegalovirus, HSV, and VZV with perinatal and maternal factors (sex, mother's ethnicity, mode of delivery, gestational age, birthweight, mother's age, mother's index of multiple deprivation, and number of previous pregnancies).

FINDINGS

In 2016, discharge rates per 100 000 infant population were 22·3 (95% CI 18·8-26·1) for congenital cytomegalovirus, 17·6 (14·6-21·1) for HSV, 32·6 (28·4-37·2) for VZV, and 0·15 (0·0-0·8) for rubella. Compared with earlier years of the study, the discharge rate in 2016 was higher for congenital cytomegalovirus, HSV, and VZV, whereas it was lower for rubella. For congenital cytomegalovirus, there was a significant step-increase between 2006 and 2007 following implementation of the NHSP (rate ratio comparing the trend line post-NHSP with that pre-NHSP 1·55 [95% CI 1·12-2·14], p=0·0072). Congenital cytomegalovirus infection was associated with birthweight less than 1 kg, maternal age younger than 25 years, socioeconomically deprived households, casearean section, and mothers of black ethnicity. Congenital HSV infection was associated with maternal age younger than 20 years, gestational age less than 32 weeks, and vaginal and emergency caesarean section deliveries, while VZV infection was associated with increased parity and black and south Asian ethnicities.

INTERPRETATION

The increase in hospital discharges coded with congenital cytomegalovirus is most likely due to the introduction of sensitive diagnostic techniques and retrospective diagnoses made in infants after implementation of the NHSP. Public health strategies to improve prevention and treatment of congenital viral infections are urgently warranted. The decrease in discharges for rubella is most likely due to the MMR vaccine.

FUNDING

None.

Specific Varicella-Related Complications and Their Decrease in Hospitalized Children after the Introduction of General Varicella Vaccination: Results from a Multicenter Pediatric Hospital Surveillance Study in Bavaria (Germany)

BACKGROUND

Universal varicella vaccination (UVV) for children introduced in Germany in 2004 resulted in a significant overall decline of varicella-related hospitalizations (VRHs). We investigated the incidence of specific types of varicella-related complications (VRCs) in hospitalized children and the impact of UVV on VRCs during the first 7 years of UVV.

METHODS

Children < 17 years of age hospitalized with an ICD-10-based (International Classification of Diseases, 10th Revision) discharge diagnosis of varicella were identified as VRH in pediatric hospitals in Bavaria by annual standardized data queries of the hospital databases (2005-2011). For each VRH, the hospitals reported basic demographic data, duration of hospital stay, all diagnostic and procedural codes, and outcome. VRCs were reported overall, per year, and by immune status. Complication rates were calculated as mean number per complication category per hospital and per year; VRC trends over time were assessed by linear regression.

RESULTS

Between 78% (2005) and 61% (2011) of Bavarian hospitals participated and reported a total of 1263 VRHs. Specific VRCs were reported in 954 (76%) children. Complication rates per hospital and year decreased from 6.7 [95% confidence interval (CI): 5.1-8.3] in 2005 to 1.5 (95% CI: 0.8-2.3) in 2011, with the strongest reduction of 90% in children < 5 years of age from 5.3 (95% CI: 4.0-6.6) in 2005 to 0.5 (95% CI: 0.1-0.9) in 2011. Significant decreases were observed for children with upper respiratory tract (URT, by 97%), lower respiratory tract (LRT, by 90%), skin (by 81%), gastrointestinal (by 78%), and neurologic (by 65%) VRCs. Forty-eight children with VRCs were immunocompromised; their annual rate decreased by 87%.

DISCUSSION

Corresponding to increasing varicella vaccination coverage in the population, the incidence of VRC decreased by 77% from 2005 to 2011, with the most substantial decrease in the target group for UVV.

CONCLUSION

Within 7 years, UVV in Germany led to a decrease of about 77% of all types of VRCs, with the highest reductions observed for VRCs of the respiratory tract.

Burden of varicella in Latin America and the Caribbean: findings from a systematic literature review

BACKGROUND

Varicella is typically mild and self-limiting, but can be associated with complications and even death. The limited data available on varicella in Latin America and the Caribbean (LAC) indicate substantial burden in countries where varicella vaccine is not part of publicly funded childhood national immunization programs.

METHODS

A systematic literature review of published studies was complemented by "gray" literature on varicella incidence, complications, mortality, and economic consequences, in the absence and presence of universal varicella vaccination (UVV) in LAC.

RESULTS

Seroprevalence data indicate that varicella is usually a disease of childhood in LAC. Varicella incidence rates, while unreliable in the absence of mandatory reporting, show a trend to increased incidence due to greater urbanization and population density. The introduction of UVV in national immunization programs has led to significant reductions in varicella incidence in these areas.

CONCLUSIONS

Varicella continues to pose a substantial healthcare burden in LAC. The future introduction of UVV in additional countries is predicted to provide substantial reductions in cases, with important economic benefits. For countries that have already implemented UVV, the challenge is to maintain high rates of coverage and, where relevant, consider inclusion of a second dose to reduce breakthrough cases. Given the significant proportion of the region now implementing UVV, a regional recommendation in order to prevent any potential for age-shifts in varicella infection might be considered.

Global impact of varicella vaccination programs

Although varicella is usually a mild and self-limited disease, complications can occur. In 1998, the World Health Organization recommended varicella vaccination for countries where the disease has a significant public health burden. Nonetheless, concerns about a shift in the disease to older groups, an increase in herpes zoster in the elderly and cost-effectiveness led many countries to postpone universal varicella vaccine introduction. In this review, we summarize the accumulating evidence, available mostly from high and middle-income countries supporting a high impact of universal vaccination in reductions of the incidence of the disease and hospitalizations and its cost-effectiveness. We have also observed the effect of herd immunity and noted that there is no definitive and consistent association between vaccination and the increase in herpes zoster incidence in the elderly.

School, child care and camp exclusion policies for chickenpox: A rational approach

Widespread varicella vaccination in Canada since 2007 has changed the epidemiology of chickenpox, with a significant decline in varicella-related hospitalizations. However, there will always be a varicella-susceptible population because of immune-compromising treatments or conditions and/or parental vaccine refusal. This document updates and replaces a 1999 statement by the Canadian Paediatric Society. The CPS position on school and child care exclusion policies has not changed since the original statement, but because there have been two published reports of varicella outbreaks associated with summer camp attendance since 1999, this revision provides additional recommendations to mitigate risk for varicella transmission at summer camps.

Early impact of universal varicella vaccination on childhood varicella and herpes zoster hospitalizations in Brazil

INTRODUCTION

The Brazilian childhood National Immunization Program (NIP) introduced live and attenuated varicella vaccination in a single dose, combined as tetraviral vaccine, at 15 months of age in the whole country, during September to December of 2013. The aim of this study was to report trends in incidence of childhood hospital admissions related to varicella and zoster in Brazil from 2003 to 2016, including the first three years after vaccine introduction.

METHODS

The number and incidence of hospital admission in patients aged less than 20 years in Brazilian public health system with an admission diagnosis of varicella and zoster from 2003 to 2016 were analyzed and pre (2003-2013) and post-vaccination periods (2014-2016) were compared. The data were obtained from DATASUS, a Brazilian government's open-access public health database system, and analyzed adjusting for secular trend and seasonality if a statistically significant change was found.

RESULTS

During the study period, 69,791 admissions due to varicella and herpes zoster occurred in the children younger than 20 years. After adjusting for seasonality, the incidence of hospitalizations decreased from 27.33 to 14.33 per 100000 per year, which corresponds to a reduction of 47.6% (95% confidence interval 18.19-77.04%, p < 0.001) in the vaccinated age group (1-4 years) in 2014-2016 compared to pre-vaccination period. The changes were not significant in the unvaccinated age groups.

CONCLUSION

The hospitalizations due to varicella and herpes zoster were decreased by half early after the introduction of a single dose of tetraviral vaccine in NIP in the vaccinated children. Further studies may assess duration and intensity of this effect, as well as the indirect effect in the unvaccinated age groups.

Safety and immunogenicity of Bio Pox™, a live varicella vaccine (Oka strain) in Indian children: A comparative multicentric, randomized phase II/III clinical trial

Varicella or chickenpox is a highly contagious disease with a high secondary attack rate. Almost 30% of Indian adolescents lack protective antibodies against varicella, emphasizing the need of routine varicella immunization. The Oka VZV is a well-established, safe and efficacious vaccine strain that is highly immunogenic and produces lifelong protective immunity. The present multicentric, open label, randomized, controlled Phase II/III study, compared the Bio Pox™ (indigenous investigational vaccine) with a licensed vaccine, Varivax™ [a][a] Please note that this article refers to the product named VARIVAX as manufactured by Changchun Keygen Biological Products Ltd., China and marketed in India by VHB Life Sciences Limited, Mumbai, and not the product VARIVAX® owned by Merck Sharp & Dohme Corp., Rahway, New Jersey, USA. Merck Sharp & Dohme Corp. have asked us to make clear that the product manufactured by Changchun Keygen Biological Products Ltd. is unrelated to and is not sponsored, endorsed or otherwise authorised by Merck Sharp & Dohme Corp. , for its safety and immunogenicity profile in 252 healthy subjects in the age group of 1-12 y (cohort I: 6-12 years, II:1-6 years) in 3 tertiary medical institutions. Antibodies were measured by VZV Glycoprotein Enzyme Linked Immunoassay (IgG ELISA) kit. Seroconversion percentage in children having pre-vaccination anti VZV IgG titer <10 mIU/mL (< 5 gp ELISA units/mL) were 80% for Bio Pox™ and 77% for Varivax™ (p = 0.692). The seroconversion rate in the group receiving Bio Pox™ was non-inferior to the group that received Varivax™. There were mild local reactions for both the vaccines; none of the patient had fever or required hospitalization or medication. The Bio Pox™ was found to be safe and immunogenic in children against VZV infection.

Economic burden of varicella in children 1-12 Years of age in Hungary, 2011-2015

Background

Although live-attenuated varicella-zoster virus (VZV) vaccines have been proven to be safe and effective in preventing varicella and real-word evidence shows routine childhood immunization programs are effective in dramatically reducing varicella associated morbidity and mortality, varicella vaccine is not included in the National Immunization Program (NIP) in Hungary. The purpose of this study was to evaluate the clinical and economic burden associated with varicella in Hungary.

Methods

This was a multicenter, retrospective, chart review study of patients aged 1–12 years with a primary varicella diagnosis between 2011 and 2015. Healthcare resource utilization (HCRU) associated with varicella, unit costs, and work loss were used to estimate direct and indirect costs. All costs are presented in 2015 HUF / Euros (€).

Results

156 children with varicella were included (75 outpatients, 81 inpatients), with a mean age of 4.4 (SD: 2.0) and 3.7 (SD: 2.1) years, respectively. One or more complications were reported by 12.0% of outpatients and 92.6% of inpatients, the most common being dehydration, skin and soft tissue infections, pneumonia, keratoconjunctivitis, and cerebellitis. HCRU estimates included use of over-the-counter (OTC) medications (96.0% outpatients, 53.1% inpatients), prescription medications (9.3% outpatients, 70.4% inpatients), tests/procedures (4.0% outpatients, 97.5% inpatients), and consultation with allied health professionals (2.7% outpatients, 30.9% inpatients). The average duration of hospital stay (inpatients) was 3.6 (95% CI: 3.2, 4.1) days. The total combined direct and indirect cost per varicella case was 228,146.7 Hungarian Forint (HUF)/€ 736.0 for inpatients and 49,790.6 HUF/€ 106.6 for outpatients. The overall annual cost of varicella in Hungary for children aged <15 years in 2015 was estimated at 1,903,332,524.3 HUF/ € 6,139,980.4.

Conclusion

Varicella is associated with substantial clinical burden in Hungary, resulting in the utilization of a significant amount of healthcare resources. These results support the need for routine vaccination of all healthy children to reduce the varicella-associated disease burden.

Severe varicella in persons vaccinated with varicella vaccine (breakthrough varicella): a systematic literature review

INTRODUCTION

Varicella vaccines are highly effective at preventing disease, but varicella may occur among vaccinated persons (termed breakthrough varicella). Breakthrough varicella is generally mild, but severe cases have been reported. The objective of this review is to describe severe breakthrough varicella. Areas covered: We conducted a systematic review of articles published during 1974-2016. A total of 34 articles were included in our review: 21 described breakthrough varicella with disseminated varicella-zoster virus (VZV) infection with other organ involvement in addition to skin (none among two-dose vaccinees); 9 described hospitalized breakthrough varicella without mention of other organ involvement in addition to skin (of which 2 reported 4 two-dose vaccinees); and 4 described both. A total of 52-60 unique breakthrough varicella cases with disseminated VZV infection with other organ involvement in addition to skin reported with the following complications, not mutually exclusive: pneumonia (n = 8-9 cases), neurologic (n = 18-24 cases), hematologic (n = 10-11 cases), ocular (n = 5 cases), renal (n = 2 cases), hepatic (n = 3 cases), secondary infection with bacteremia or sepsis (n = 8 cases), and other complication (n = 4 cases). There were 6 cases of fatal breakthrough varicella. Expert commentary: With >31 million doses distributed annually worldwide since 2007, severe breakthrough varicella can occur but they appear to be uncommon.

Decline of Neurologic Varicella Complications in Children During the First Seven Years After Introduction of Universal Varicella Vaccination in Germany, 2005-2011

BACKGROUND

Universal varicella vaccination for 1-year-old children was introduced in Germany in 2004. We investigated changes in the incidence and type of varicella-associated neurologic complications in children during the first 7 years after universal vaccination recommendation.

METHODS

A surveillance study was conducted based on patients <17 years of age with an International Classification of Diseases (10th Revision) discharge diagnosis of varicella, annually reported by 22-29 pediatric hospitals in Bavaria, Germany, 2005 to 2011. Annual incidences were estimated and linear trend across years was assessed by Poisson regression models.

RESULTS

Of a total of 1263 varicella-associated pediatric hospitalizations, 228 children (18.1%) had neurologic complications (median age 4 years, interquartile range 2-7; 56% male). The most frequent neurologic complications were febrile convulsion (32.0% of 228 children, median age 3.0 years), varicella encephalitis or meningitis (28.9%; median age 4.5 years), syncope (13.2%; median age 7.0 years) and cerebral convulsion (11.0%; median age 4.0 years). Other complications included ataxia (3.1%), facial nerve palsy (2.6%) and cerebral vasculitis/infarction (1.8%). Neurologic complications showed a continuous decrease between 2005 and 2011, from an incidence of 2.8 (95% confidence interval: 2.1-3.6) per 100,000 children <17 years of age to 1.2 (95% confidence interval: 0.7-2.1; P < 0.001). In particular, a marked decline was observed among children up to 7 years of age, mainly because of a decrease in the number of febrile convulsions and encephalitis or meningitis.

CONCLUSION

The incidence of varicella-associated neurologic complications in children decreased approximately by 60% during the first 7 years following the recommendation for universal vaccination.

Global Varicella Vaccine Effectiveness: A Meta-analysis

CONTEXT

Several varicella vaccines are available worldwide. Countries with a varicella vaccination program use 1- or 2-dose schedules.

OBJECTIVE

We examined postlicensure estimates of varicella vaccine effectiveness (VE) among healthy children.

DATA SOURCES

Systematic review and descriptive and meta-analysis of Medline, Embase, Cochrane libraries, and CINAHL databases for reports published during 1995-2014.

STUDY SELECTION

Publications that reported original data on dose-specific varicella VE among immunocompetent children.

DATA EXTRACTION

We used random effects meta-analysis models to obtain pooled one dose VE estimates by disease severity (all varicella and moderate/severe varicella). Within each severity category, we assessed pooled VE by vaccine and by study design. We used descriptive statistics to summarize 1-dose VE against severe disease. For 2-dose VE, we calculated pooled estimates against all varicella and by study design.

RESULTS

The pooled 1-dose VE was 81% (95% confidence interval [CI]: 78%-84%) against all varicella and 98% (95% CI: 97%-99%) against moderate/severe varicella with no significant association between VE and vaccine type or study design (P > .1). For 1 dose, median VE for prevention of severe disease was 100% (mean = 99.4%). The pooled 2-dose VE against all varicella was 92% (95% CI: 88%-95%), with similar estimates by study design.

LIMITATIONS

VE was assessed primarily during outbreak investigations and using clinically diagnosed varicella.

CONCLUSIONS

One dose of varicella vaccine was moderately effective in preventing all varicella and highly effective in preventing moderate/severe varicella, with no differences by vaccine. The second dose adds improved protection against all varicella.

Hospitalization with varicella and shingles before and after introduction of childhood varicella vaccination in Germany

In Germany, one dose of varicella vaccination has been recommended for children aged <24 months since 2004, and 2 doses have been recommended since 2009. Vaccination coverage (VC) is above 80% for one dose and 60% for 2 doses. In this study, data on varicella- and shingles-associated hospitalizations before and after vaccine introduction were assessed. Based on ICD-coded data of the main diagnosis of hospitalized cases from 1995-2012 in Germany, annual age-adjusted and age-specific hospitalization incidences (cases/100,000; HI) were calculated. HI means 1995-2003 (pre-vaccination-period) versus 2005-2012 (post-vaccination-period) were compared. Age-specific trends and annual percentage change rates (APC) were assessed by joinpoint regression. Overall age-adjusted varicella-HI decreased from 3.3/100,000 pre-vaccination to 1.9/100,000 post vaccination. The decline was greatest in regions with the highest VC. The post-vaccination decline was greatest in children aged <1, 1-4, and 5-9 y, who had APCs of -18.2,-27.2 and -15.2, respectively, and significant joinpoints. In all other age groups no post-vaccination joinpoints were detected or they did not lead to a consistent trend. Age-adjusted shingles-HI increased from 8.8/100,000 (1995) to 16.8/100,000 (2012). Shingles-HI increased in all age groups with no significant post-vaccination joinpoints, except in children<1 and 1-4 y, where APCs of -5.6 and -3.6 were detected. Varicella vaccination significantly reduced varicella-HI in children below 10 y, but was not definitely related to varicella-HI in older age groups. A consistent increase of shingles-HI began before varicella vaccination was introduced and was not affected by vaccination.

A spot of bother: Why varicella vaccine programs matter

Objective

To evaluate Ontario's provincial varicella vaccination program through analysis of aggregate varicella cases in order to determine whether there has been a decrease in reportable disease burden; and to assess varicella vaccine adverse events following immunization (AEFIs).

Methods

Aggregate varicella cases (1993-2013) were extracted from the reportable disease databases. Pre-program (1993-2004) and post-program (2007-2013) periods were chosen according to implementation of the publicly funded vaccination program. AEFIs following administration of varicella vaccines (2010-2013) were also extracted. Reporting rates were calculated using net doses distributed as the denominator. Serious AEFIs were defined using World Health Organization standards.

Results

The incidence of aggregate varicella reports decreased significantly over the study period (from 311.4 to 22.2 cases per 100,000 population in 1993 and 2013, respectively). Incidence also decreased significantly in all age groups between the pre- and the post-program periods with a shift in age distribution towards older individuals in the post-program period. A total of 162 AEFIs following varicella vaccine were reported between 2010 and 2013 for an annualized reporting rate of 14.6 per 100,000 doses distributed. The most common events were rash (37.3%), including eight reports of varicella-like rash (0.7 per 100,000 doses distributed). Ten serious events were reported (0.9 per 100,000 doses distributed), and all vaccine recipients recovered.

Conclusion

Significant reductions in varicella disease incidence and low AEFI reporting rates were observed with the introduction of the publicly funded varicella vaccine program in Ontario. Continued surveillance is indicated to further assess trends in varicella disease and vaccine safety.

Twenty Years of Medically-Attended Pediatric Varicella and Herpes Zoster in Ontario, Canada: A Population-Based Study

OBJECTIVE

To determine if reductions in medically-attended pediatric varicella and herpes zoster occurred in Ontario, Canada, after publicly-funded varicella immunization was implemented in 2004.

METHODS

For fiscal years (FY) 1992-2011, we examined data on varicella and herpes zoster physician office visits, emergency department (ED) visits, hospitalizations (including for varicella-associated skin and soft tissue infections [SSTI]), and intensive care unit (ICU) admissions, among those aged <18 years. The pre-vaccine, privately-available, and vaccine program eras were FY1992-1998, FY1999-2003, and FY2004-2011, respectively. We used Poisson regressionand Kruskal-Wallis tests (all at the p<0.05 level of significance), and compared rates using incidence rate ratios (IRRs) and 95% confidence intervals (CIs).

RESULTS

Incidence of varicella office visits declined over the study period from a high of 25.1/1,000 in FY1994 to a low of 3.2/1,000 in FY2011. ED visits and hospitalizations followed similar patterns of decreasing rates later in the study period. IRRs comparing the vaccine program versus pre-vaccine eras were 0.29 (95%CI: 0.26-0.32) for office visits, 0.29 (95%CI: 0.21-0.40) for ED visits, and 0.41 (95%CI: 0.10-1.69) for hospitalizations. Annual declines in varicella office visits were 7.7%, 9.1%, 8.4%, and 8.4% per year among children aged <1 year, 1-4 years, 5-11 years, and ≥12 years, respectively (all p<0.001). Age-specific rates of varicella-associated SSTI declined significantly among children <12 years (p<0.001) and rates of ICU admissions decreased significantly for children <1 year (p = 0.02). (p<0.001) over the study period. For children aged 5-17 years, herpes zoster office visits decreased whereas ED visits increased (both p<0.001) and there was a small, non-significant (p = 0.07), decrease in hospitalizations.

CONCLUSION

Medically-attended varicella decreased during the study period, particularly since varicella vaccine was publicly-funded. Results suggest immunization program-related changes in varicella epidemiology, including herd effects, demonstrated by reductions in varicella in program-ineligible age groups. We did not observe a consistent impact on herpes zoster.

Successes and challenges in varicella vaccine

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

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

OBJECTIVE

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

METHODS

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

FINDINGS

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

CONCLUSION

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

[Varicella vaccination in Germany. A provisional appraisal in the context of MMR vaccination]

In 2004, a general varicella immunization was introduced in Germany for infants from the age of 11 months, followed by the subsequent recommendation in 2009 of a second vaccine dose. The vaccination is carried out at the same time as the immunization against measles, mumps, and rubella (MMR). Results of the nationwide sentinel surveillance of varicella and herpes zoster implemented by the Varicella Working Group (Arbeitsgemeinschaft Varizellen, AGV) show that the defined goals for varicella immunization (reduction of varicella-related morbidity, complications and hospitalizations) have been reached within a few years owing to the advances in vaccine coverage. Although coverage rates for varicella have not yet reached the same levels as for MMR, varicella immunization seems to have benefited from the established MMR immunization schedule. Moreover, there is no evidence for an adverse effect on the use and acceptance of the MMR vaccine. Lessons learnt in measles epidemiology (such as trends in the incidence of the disease in adolescents and infants), as well as in the history of MMR recommendations, may be useful for the evaluation of future epidemiological changes with respect to varicella and herpes zoster. In view of a rapidly waning immunity against the varicella zoster virus after vaccination with one dose and the lifelong persistence of the virus, achieving a robust and sustainable immunity in the general population seems to be an ambitious goal. However, this accomplishment will be indispensable in preventing breakthrough infections and a shift of varicella to older ages and in avoiding an increase in herpes zoster incidence.

Antimicrobial stewardship in daily practice: Managing an important resource

Antimicrobial stewardship is a recent concept that embodies the practical, judicious use of antimicrobials to decrease adverse outcomes from antimicrobials while optimizing the treatment of bacterial infections to reduce the emergence of resistant pathogens. The objectives of the present statement are to illustrate the principles of antimicrobial stewardship and to offer practical examples of how to make antimicrobial stewardship part of everyday hospital and outpatient practice. Vital components of antimicrobial stewardship include appropriate testing to diagnose whether infections are viral or bacterial, and using clinical follow-up rather than antibiotics in cases in which the child is not very ill and uncertainty exists. Other specific, important actions include questioning whether positive urine cultures are contaminated when there is no evidence of pyuria or inflammatory changes, and obtaining a chest radiograph to support a diagnosis of bacterial pneumonia. Optimizing the choice and dosage of antimicrobials also reduces the probability of clinical failures and subsequent courses of antimicrobials. A list of common clinical scenarios to promote stew-ardship is included.

Varicella routine vaccination and the effects on varicella epidemiology - results from the Bavarian Varicella Surveillance Project (BaVariPro), 2006-2011

BACKGROUND

In 2004, routine varicella vaccination was recommended in Germany for children 11-14 months of age with one dose, and since 2009, with a second dose at 15-23 months of age. The effects on varicella epidemiology were investigated.

METHODS

Data on varicella vaccinations, cases and complications were collected from annual parent surveys (2006-2011), monthly paediatric practice surveillance (Oct 2006 - Sep 2011; five varicella seasons) and paediatric hospital databases (2005-2009) in the area of Munich (about 238,000 paediatric inhabitants); annual incidences of cases and hospitalisations were estimated.

RESULTS

Varicella vaccination coverage (1st dose) in children 18-36 months of age increased in two steps (38%, 51%, 53%, 53%, 66% and 68%); second-dose coverage reached 59% in the 2011 survey. A monthly mean of 82 (62%) practices participated; they applied a total of 50,059 first-dose and 40,541 second-dose varicella vaccinations, with preferential use of combined MMR-varicella vaccine after recommendation of two doses, and reported a total of 16,054 varicella cases <17 years of age. The mean number of cases decreased by 67% in two steps, from 6.6 (95%CI 6.1-7.0) per 1,000 patient contacts in season 2006/07 to 4.2 (95%CI 3.9-4.6) in 2007/08 and 4.0 (95%CI 3.6-4.3) in 2008/09, and further to 2.3 (95%CI 2.0-2.6) in 2009/10 and 2.2 (95%CI 1.9-2.5) in 2010/11. The decrease occurred in all paediatric age groups, indicating herd protection effects. Incidence of varicella was estimated as 78/1,000 children <17 years of age in 2006/07, and 19/1,000 in 2010/11. Vaccinated cases increased from 0.3 (95%0.2-0.3) per 1,000 patient contacts in 2006/07 to 0.4 (95%CI 0.3-0.5) until 2008/09 and decreased to 0.2 (95%CI 0.2-0.3) until 2010/11. The practices treated a total of 134 complicated cases, mainly with skin complications. The paediatric hospitals recorded a total of 178 varicella patients, including 40 (22.5%) with neurological complications and one (0.6%) fatality due to varicella pneumonia. Incidence of hospitalisations decreased from 7.6 per 100,000 children <17 years of age in 2005 to 4.3 in 2009, and from 21.0 to 4.7 in children <5 years of age.

CONCLUSIONS

Overall, the results show increasing acceptance and a strong impact of the varicella vaccination program, even with still suboptimal vaccination coverage.