Varicella prevention in the United States: a review of successes and challenges

Protection against varicella with two doses of combined measles-mumps-rubella-varicella vaccine versus one dose of monovalent varicella vaccine: a multicentre, observer-blind, randomised, controlled trial

BACKGROUND

Rates of varicella have decreased substantially in countries implementing routine varicella vaccination. Immunisation is possible with monovalent varicella vaccine or a combined measles-mumps-rubella-varicella vaccine (MMRV). We assessed protection against varicella in naive children administered one dose of varicella vaccine or two doses of MMRV.

METHODS

This study was done in ten European countries with endemic varicella. Healthy children aged 12-22 months were randomised (3:3:1 ratio, by computer-generated randomisation list, with block size seven) to receive 42 days apart (1) two doses of MMRV (MMRV group), or (2) MMR at dose one and monovalent varicella vaccine at dose two (MMR+V group), or (3) two doses of MMR (MMR group; control). Participants and their parents or guardians, individuals involved in assessment of any outcome, and sponsor staff involved in review or analysis of data were masked to treatment assignment. The primary efficacy endpoint was occurrence of confirmed varicella (by detection of varicella zoster virus DNA or epidemiological link) from 42 days after the second vaccine dose to the end of the first phase of the trial. Cases were graded for severity. Efficacy analyses were per protocol. Safety analyses included all participants who received at least one vaccine dose. This trial is registered with ClinicalTrials.gov, number NCT00226499.

FINDINGS

Between Sept 1, 2005, and May 10, 2006, 5803 children (mean age 14·2 months, SD 2·5) were vaccinated. In the efficacy cohort of 5285 children, the mean duration of follow-up in the MMRV group was 36 months (SD 8·8), in the MMR+V group was 36 months (8·5) and in the MMR group was 35 months (8·9). Varicella cases were confirmed for 37 participants in the MMRV group (two moderate to severe), 243 in the MMR+V group, and 201 in the MMR group. Second cases occurred for three participants (all in the MMR+V group). Varicella cases were moderate to severe for two participants in the MMRV group, 37 in the MMR+V group (one being a second case that followed a mild first case); and 117 in the MMR group. Efficacy of two-dose MMRV against all varicella was 94·9% (97·5% CI 92·4-96·6), and against moderate to severe varicella was 99·5% (97·5-99·9). Efficacy of one-dose varicella vaccine against all varicella was 65·4% (57·2-72·1), and against moderate to severe varicella (post hoc) was 90·7% (85·9-93·9). The most common adverse event in all groups was injection-site redness (up to 25% of participants). Within 15 days after dose one, 57·4% (95% CI 53·9-60·9) of participants in the MMRV group reported fever of 38°C or more, by contrast with 44·5% (41·0-48·1) with MMR+V, and 39·8% (33·8-46·1) with MMR. Eight serious adverse events were deemed related to vaccination (three MMRV, four MMR+V, one MMR). All resolved within the study period.

INTERPRETATION

These results support the implementation of two-dose varicella vaccination on a short course, to ensure optimum protection from all forms of varicella disease.

FUNDING

GlaxoSmithKline Vaccines.

Clinical and molecular aspects of the live attenuated Oka varicella vaccine

VZV is a ubiquitous member of the Herpesviridae family that causes varicella (chicken pox) and herpes zoster (shingles). Both manifestations can cause great morbidity and mortality and are therefore of significant economic burden. The introduction of varicella vaccination as part of childhood immunization programs has resulted in a remarkable decline in varicella incidence, and associated hospitalizations and deaths, particularly in the USA. The vaccine preparation, vOka, is a live attenuated virus produced by serial passage of a wild-type clinical isolate termed pOka in human and guinea pig cell lines. Although vOka is clinically attenuated, it can cause mild varicella, establish latency, and reactivate to cause herpes zoster. Sequence analysis has shown that vOka differs from pOka by at least 42 loci; however, not all genomes possess the novel vOka change at all positions, creating a heterogeneous population of genetically distinct haplotypes. This, together with the extreme cell-associated nature of VZV replication in cell culture and the lack of an animal model, in which the complete VZV life cycle can be replicated, has limited studies into the molecular basis for vOka attenuation. Comparative studies of vOka with pOka replication in T cells, dorsal root ganglia, and skin indicate that attenuation likely involves multiple mutations within ORF 62 and several other genes. This article presents an overview of the clinical aspects of the vaccine and current progress on understanding the molecular mechanisms that account for the clinical phenotype of reduced virulence.

Disease burden of herpes zoster in Sweden--predominance in the elderly and in women - a register based study

Background

The herpes zoster burden of disease in Sweden is not well investigated. There is no Swedish immunization program to prevent varicella zoster virus infections. A vaccine against herpes zoster and its complications is now available. The aim of this study was to estimate the herpes zoster burden of disease and to establish a pre-vaccination baseline of the minimum incidence of herpes zoster.

Methods

Data were collected from the Swedish National Health Data Registers including the Patient Register, the Pharmacy Register, and the Cause of Death Register. The herpes zoster burden of disease in Sweden was estimated by analyzing the overall, and age and gender differences in the antiviral prescriptions, hospitalizations and complications during 2006-2010 and mortality during 2006-2009.

Results

Annually, 270 per 100,000 persons received antiviral treatment for herpes zoster, and the prescription rate increased with age. It was approximately 50% higher in females than in males in the age 50+ population (rate ratio 1.39; 95% CI, 1.22 to 1.58). The overall hospitalization rate for herpes zoster was 6.9/100,000 with an approximately three-fold increase for patients over 80 years of age compared to the age 70-79 group. A gender difference in hospitalization rates was observed: 8.1/100,000 in females and 5.6/100,000 in males. Herpes zoster, with a registered complication, was found in about one third of the hospitalized patients and the most common complications involved the peripheral and central nervous systems. Death due to herpes zoster was a rare event.

Conclusions

The results of this study demonstrate the significant burden of herpes zoster disease in the pre-zoster vaccination era. A strong correlation with age in the herpes zoster- related incidence, hospitalization, complications, and mortality rates was found. In addition, the study provides further evidence of the female predominance in herpes zoster disease.

Varicella-zoster virus vaccine, successes and difficulties

Despite intensive efforts in recent decades to develop preventive or therapeutic vaccines against diseases caused by herpes simplex virus (HSV), or varicella-zoster virus (VZV), members of the Alpha herpes virinae subfamily of human herpes viruses,a safe and efficient vaccine has been approved for commercial development only against VZV. The VZV vaccine contains a live attenuated strain, OKA. It consists of amixture of at least 13 subpopulations of viruses, all with deletions, insertions or mutations in the genome; the most common mutations are observed in the open reading frame 62 (ORF62). Experience over more than 30 years in Japan, the USA and other countries where VZV vaccination is provided has demonstrated that the vaccine is safe and the effectiveness of two doses compared to unvaccinated children is 98-99%. When administered in a higher dose to stimulate the declining cell-mediated immunity, the same vaccine has been shown to reduce the incidence and severity of herpes zoster in immunocompetent individuals older than 60 years. Vaccination of immuno-compromised subjects with this VZV vaccine is problematic and various strategies need to be explored. Differences in the pathomechanisms of infection, latency and immune evasion of VZV and HSV, together with host genetic factors, may explain the availability of the successful VZV vaccine and the failures of the past HSV vaccine candidates.

Different vaccination strategies in Spain and its impact on severe varicella and zoster

Varicella vaccines available in Spain were marketed in 1998 and 2003 for non-routine use. Since 2006 some regions decided to include varicella vaccination in their regional routine vaccination programmes at 15-18 months of age. Other regions chose the strategy of vaccinating susceptible adolescents. This study shows the trends in severe varicella zoster virus infections through the analysis of the hospital discharges related to varicella and herpes zoster in the general population from 2005 to 2010 in Spain. A total of 11,125 hospital discharges related to varicella and 27,736 related to herpes zoster were reported during the study period. The overall annual rate of hospitalization was 4.14 cases per 100,000 for varicella and 10.33 cases per 100,000 for herpes zoster. In children younger than 5 years old varicella hospitalization rate significantly decreased from 46.77 in 2005 to 26.55 per 100,000 in 2010. The hospitalization rate related to herpes zoster slightly increased from 9.71 in 2005 to 10.90 per 100,000 in 2010. This increase was mainly due to the significant increase occurring in the >84 age group, from 69.55 to 97.68 per 100,000. When gathering for regions taking into account varicella vaccine strategy, varicella related hospitalizations decreased significantly more in those regions which included the vaccine at 15-18 months of age as a routine vaccine comparing with those vaccinating at 10-14 years old. No significant differences were found in herpes zoster hospitalization rates regarding the varicella vaccination strategy among regions. Severe varicella infections decreased after implementation of varicella vaccination in Spain. This decrease was significantly higher in regions including the vaccine at 15-18 months of age compared with those vaccinating susceptible adolescents.

Impact of a routine two-dose varicella vaccination program on varicella epidemiology

OBJECTIVE

One-dose varicella vaccination for children was introduced in the United States in 1995. In 2006, a second dose was recommended to further decrease varicella disease and outbreaks. We describe the impact of the 2-dose vaccination program on varicella incidence, severity, and outbreaks in 2 varicella active surveillance areas.

METHODS

We examined varicella incidence rates and disease characteristics in Antelope Valley (AV), CA, and West Philadelphia, PA, and varicella outbreak characteristics in AV during 1995-2010.

RESULTS

In 2010, varicella incidence was 0.3 cases per 1000 population in AV and 0.1 cases per 1000 population in West Philadelphia: 76% and 67% declines, respectively, since 2006 and 98% declines in both sites since 1995; incidence declined in all age groups during 2006-2010. From 2006-2010, 61.7% of case patients in both surveillance areas had been vaccinated with 1 dose of varicella vaccine and 7.5% with 2 doses. Most vaccinated case patients had <50 lesions with no statistically significant differences among 1- and 2-dose cases (62.8% and 70.3%, respectively). Varicella-related hospitalizations during 2006-2010 declined >40% compared with 2002-2005 and >85% compared with 1995-1998. Twelve varicella outbreaks occurred in AV during 2007-2010, compared with 47 during 2003-2006 and 236 during 1995-1998 (P < .01).

CONCLUSIONS

Varicella incidence, hospitalizations, and outbreaks in 2 active surveillance areas declined substantially during the first 5 years of the 2-dose varicella vaccination program. Declines in incidence across all ages, including infants who are not eligible for varicella vaccination, and adults, in whom vaccination levels are low, provide evidence of the benefit of high levels of immunity in the population.

Breakthrough varicella in a cancer patient with persistent varicella antibody after one varicella vaccination

A boy with Hodgkin disease contracted breakthrough varicella from his father, who had chickenpox. The boy had received a single varicella vaccination and was seropositive by enzyme-linked immunosorbent assay before being diagnosed with breakthrough varicella. Seropositivity after a single varicella vaccination does not guarantee complete protection in an immunocompromised child.

Varicella and secondary pneumonia in a healthy child: is it time to introduce varicella vaccine in the UK?

A previously healthy 8-month-old boy presented to the emergency department with a 1-week history of chickenpox infection. His routine immunizations were up-to-date. His parents reported a high temperature (up to 39.5°C) in the preceding 48 hours and that he also had a mild cough, episodes of vomiting and loose stools. He had fed poorly in the 24 hours before presentation. Clinical assessment revealed a temperature of 36.7°C, heart rate 130/min, respiratory rate of 34/min and crusted chickenpox lesions. The infant was alert, smiling and playful, and systemic examination was otherwise unremarkable. He was admitted for monitoring of his fluid intake and temperature. As the infant continued to vomit intermittently in the 6 hours post admission, blood investigations were done and intravenous fluids were commenced. Laboratory investigations did not reveal biochemical evidence of dehydration, but they did show raised inflammatory markers: white blood cell count 24.8 × 109/litre, neutrophil count 19.8 × 109/litre and C-reactive protein 227mg/litre. In view of these results and the ongoing high fever, a chest X-ray was performed, revealing right upper lobe consolidation and collapse (Figure 1). Oral amoxicillin and flucloxacillin were started and oral feeding was successfully reestablished over the next 24 hours. He was discharged home after 48 hours, to complete a full 7-day course of oral antibiotics.

Pathogenesis and current approaches to control of varicella-zoster virus infections

Varicella-zoster virus (VZV) was once thought to be a fairly innocuous pathogen. That view is no longer tenable. The morbidity and mortality due to the primary and secondary diseases that VZV causes, varicella and herpes zoster (HZ), are significant. Fortunately, modern advances, including an available vaccine to prevent varicella, a therapeutic vaccine to diminish the incidence and ameliorate sequelae of HZ, effective antiviral drugs, a better understanding of VZV pathogenesis, and advances in diagnostic virology have made it possible to control VZV in the United States. Occult forms of VZV-induced disease have been recognized, including zoster sine herpete and enteric zoster, which have expanded the field. Future progress should include development of more effective vaccines to prevent HZ and a more complete understanding of the consequences of VZV latency in the enteric nervous system.

The effectiveness of varicella vaccination in children in Germany: a case-control study

BACKGROUND

Effectiveness of 1 dose of varicella vaccination was estimated to be 85-88% against clinical varicella of any severity in case-control studies in non-European countries, but lower effectiveness has been demonstrated in outbreaks.

METHODS

A prospective, age- and practice-matched case-control study was conducted in Germany to assess the effectiveness of 1 dose of OKA/GSK varicella vaccine (derived from the OKA strain, a Japanese clinical isolate) and of any varicella vaccine (including OKA/GSK, OKA/Merck and MMR-OKA/GSK) against polymerase chain reaction (PCR)-confirmed varicella under conditions of routine use.

RESULTS

The cohort included 432 PCR-confirmed cases and 432 matched controls (1-7 years old). Varicella vaccination was reported for 13.2% (57/432) of cases and 45.1% (195/432) of controls. Median time since vaccination was 28 and 25 months, respectively. Vaccinated cases experienced milder disease (P < 0.0001) and shorter duration of disease (P = 0.004) compared with unvaccinated cases. After adjusting for gender and school/day-care attendance, vaccine effectiveness of 1 dose of OKA/GSK against PCR-confirmed varicella of any severity was 71.5% (95% confidence interval [CI]: 49.1-84.0) and 94.7% (95% CI: 77.8-98.7) against PCR-confirmed moderate or severe varicella. Adjusted effectiveness for any varicella vaccine was 86.4% (95% CI: 77.3-91.8) against any severity and 97.7% (95% CI: 90.5-99.4) against moderate or severe varicella.

CONCLUSIONS

One dose of varicella vaccine provided high protection against moderate and severe varicella disease for a period of up to 5 years after vaccination. However, further effectiveness data are needed to assess long-term protection.

Varicella vaccine uptake and associated factors in children in Hong Kong

Varicella is a common and highly contagious childhood disease which impacts the public worldwide. Hong Kong children can only be vaccinated against the disease in private practice. The varicella vaccination rate of local children in preschool is uncertain. Therefore a cross-sectional kindergarten-based parent-administered questionnaire survey was conducted in Hong Kong during 2012. Twelve kindergartens were randomly selected from a complete school list from the Education Bureau of Hong Kong. In total, 1285/1538 (83·6%) parents consented to join the study and completed the questionnaires. The overall varicella infection rate was 19·5% and the uptake of varicella vaccination rate was 57·6%. Barriers against varicella vaccination were mostly due to parental uncertainties about the effectiveness of vaccine, lack of recommendations from doctors or government, and adverse side-effects of the vaccine. The government and healthcare professional bodies are strongly recommended to further enhance health education among healthcare professionals, encouraging their active promotion of varicella vaccination for their patients. Furthermore, health education through various stakeholders is crucial to enhance parental awareness of varicella, as well as the effectiveness and safety of varicella vaccine.

Three-dimensional normal human neural progenitor tissue-like assemblies: a model of persistent varicella-zoster virus infection

Varicella-zoster virus (VZV) is a neurotropic human alphaherpesvirus that causes varicella upon primary infection, establishes latency in multiple ganglionic neurons, and can reactivate to cause zoster. Live attenuated VZV vaccines are available; however, they can also establish latent infections and reactivate. Studies of VZV latency have been limited to the analyses of human ganglia removed at autopsy, as the virus is strictly a human pathogen. Recently, terminally differentiated human neurons have received much attention as a means to study the interaction between VZV and human neurons; however, the short life-span of these cells in culture has limited their application. Herein, we describe the construction of a model of normal human neural progenitor cells (NHNP) in tissue-like assemblies (TLAs), which can be successfully maintained for at least 180 days in three-dimensional (3D) culture, and exhibit an expression profile similar to that of human trigeminal ganglia. Infection of NHNP TLAs with cell-free VZV resulted in a persistent infection that was maintained for three months, during which the virus genome remained stable. Immediate-early, early and late VZV genes were transcribed, and low-levels of infectious VZV were recurrently detected in the culture supernatant. Our data suggest that NHNP TLAs are an effective system to investigate long-term interactions of VZV with complex assemblies of human neuronal cells.

Varicella-zoster virus (VZV), the alphaherpesvirus that typically causes childhood chickenpox and shingles in adults, becomes latent in neurons, thus remaining in the body for a lifetime. Unfortunately, few models are available to study the establishment of VZV latency since the virus infects only humans and establishes persistent infections and latency only in neurons, a slowly proliferating, short-lived cell in culture. We have successfully maintained normal human neural progenitor cells (NHNP) in tissue-like assemblies (TLAs) in 3-dimensional (3D) cultures for up to 6 months. The 3D NHNP TLAs show some characteristics as those found in the human trigeminal ganglia, the site of VZV latency. NHNP TLAs infected with VZV remain viable for 3 months during which time VZV DNA replicates and remains genetically stable, virus genes are transcribed, and infectious VZV is sporadically released. The ability to maintain VZV infected NHNP cells in culture for extended times provides the unique opportunity to study the molecular interactions between this important human pathogen and neuronal tissue to an extent previously unattainable.

Varicella zoster virus in American Samoa: seroprevalence and predictive value of varicella disease history in elementary and college students

The epidemiology of varicella is believed to differ between temperate and tropical countries. We conducted a varicella seroprevalence study in elementary and college students in the US territory of American Samoa before introduction of a routine varicella vaccination programme. Sera from 515 elementary and 208 college students were tested for the presence of varicella-zoster virus (VZV) IgG antibodies. VZV seroprevalence increased with age from 76·0% in the 4-6 years group to 97·7% in those aged ⩾23 years. Reported history of varicella disease for elementary students was significantly associated with VZV seropositivity. The positive and negative predictive values of varicella disease history were 93·4% and 36·4%, respectively, in elementary students and 97·6% and 3·0%, respectively, in college students. VZV seroprevalence in this Pacific island appears to be similar to that in temperate countries and suggests endemic VZV circulation.

A population based study of the epidemiology of Herpes Zoster and its complications

OBJECTIVES

To assess the incidence of Herpes Zoster (HZ) and its complications in the Israeli general population and specifically in immune-compromised individuals, and to identify risk factors for developing HZ and post-herpetic neuralgia (PHN).

METHODS

A retrospective database search for newly diagnosed cases of HZ and of PHN during 2006-2010 was conducted using the comprehensive longitudinal database of Maccabi Health Services. Cox-proportional hazards models were used to assess associations between risk factors and HZ and PHN.

RESULTS

During 2006-2010 there were 28,977 newly diagnosed cases of HZ and 1508 newly diagnosed cases of PHN. Incidence density rate of HZ was 3.46 per 1000 person-years in the total population and 12.8 per 1000 person-years in immune-compromised patients. HZ and PHN incidence increased sharply with age. 12.4% and 3.1% of elderly HZ patients (≥ 65 years) developed PHN or ophthalmic complications, respectively. In multivariable analyses, HZ and PHN were associated with female sex, higher socioeconomic status, diabetes mellitus, cancer history, and HIV treatment.

CONCLUSIONS

Extrapolating to the entire Israeli population, we estimate over 24,000 new cases of HZ and 1250 new cases of PHN each year. Cost-effectiveness analysis should be performed to determine the threshold age for vaccination against HZ.

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.

Cycling probe technology to quantify and discriminate between wild-type varicella-zoster virus and Oka vaccine strains

Rapid differentiation between wild-type varicella zoster virus (VZV) and Oka-vaccine (vOka) strains is important for monitoring side reactions of varicella vaccination. To develop a high-throughput molecular diagnostic method for the differentiation of wild-type VZV and vOka strains based on cycling probe technology. The primers were designed to amplify common sequences spanning a single nucleotide polymorphism (SNP) in gene 62 of VZV. DNA-RNA chimeric probes (cycling probes) were designed to detect the SNP at nucleotide 105705. The cycling probe real-time PCR assays for VZV wild-type and vOka strains specifically amplified plasmids containing target sequences that ranged between 10 and 1×10(6) copies per reaction. The inter- and intra-assay coefficients of variation were less than 5%. After initial validation studies, the clinical reliability of this method was evaluated using 38 swab samples that were collected from patients suspected of being zoster. Compared to the loop mediated isothermal amplification method, which is defined as the gold standard, cycling probe real-time PCR was highly sensitive and specific. The cycling probe real-time PCR technology is a reliable tool for differentiating between wild-type VZV and vOka strains in clinical samples.

Factors associated with receipt of two doses of varicella vaccine among adolescents in the United States

BACKGROUND

In 2006, routine two-dose varicella vaccination for all children was recommended, including a second dose catch-up program for older children and adolescents. Recent studies have shown that a second dose of the vaccine provides incremental protection against varicella disease.

METHODS

This study is a cross-sectional analysis of data collected in the National Immunization Survey-Teen 2010 combined with publicly available data related to state immunization requirements. Bivariate and multivariable logistic regression analyses were performed to examine individual-level and state-level factors associated with receipt of two doses of varicella vaccine among 10,542 adolescents 13 to 17 years of age with no history of varicella.

RESULTS

Overall, 58.1% of adolescents without any history of varicella had received two doses of varicella vaccine. Coverage varied widely among states, ranging from 19.7% in South Dakota to 85.3% in Rhode Island. In the multivariable model, receipt of two doses of varicella vaccine was significantly associated with younger age, higher maternal education level, private health insurance, more frequent health care visits, receipt of both quadrivalent meningococcal conjugate and tetanus, diphtheria, and acellular pertussis vaccinations, and residing in a state with two-dose policies for middle school entry. Vaccines for Children program-eligible adolescents were less likely to have received two doses.

CONCLUSION

Two-dose varicella vaccination coverage remained low among adolescents in 2010, despite the universal recommendation. Programs that are aimed specifically at Vaccines for Children program-eligible adolescents, state policies requiring two doses for middle school entry, and broad education and implementation of the adolescent vaccination platform may help to improve varicella vaccination coverage.

Perspectives on the impact of varicella immunization on herpes zoster. A model-based evaluation from three European countries

The introduction of mass vaccination against Varicella-Zoster-Virus (VZV) is being delayed in many European countries because of, among other factors, the possibility of a large increase in Herpes Zoster (HZ) incidence in the first decades after the initiation of vaccination, due to the expected decline of the boosting of Cell Mediated Immunity caused by the reduced varicella circulation. A multi-country model of VZV transmission and reactivation, is used to evaluate the possible impact of varicella vaccination on HZ epidemiology in Italy, Finland and the UK. Despite the large uncertainty surrounding HZ and vaccine-related parameters, surprisingly robust medium-term predictions are provided, indicating that an increase in HZ incidence is likely to occur in countries where the incidence rate is lower in absence of immunization, possibly due to a higher force of boosting (e.g. Finland), whereas increases in HZ incidence might be minor where the force of boosting is milder (e.g. the UK). Moreover, a convergence of HZ post vaccination incidence levels in the examined countries is predicted despite different initial degrees of success of immunization policies. Unlike previous model-based evaluations, our investigation shows that after varicella immunization an increase of HZ incidence is not a certain fact, rather depends on the presence or absence of factors promoting a strong boosting intensity and which might or not be heavily affected by changes in varicella circulation due to mass immunization. These findings might explain the opposed empirical evidences observed about the increases of HZ in sites where mass varicella vaccination is ongoing.

Herpes zoster and radiation therapy: what radiation oncologists need to know about diagnosing, preventing, and treating herpes zoster

Herpes zoster, a viral disease that is characterized by a painful and blistering eruption in the skin, represents reactivation of latent varicella zoster (chickenpox) virus infection. In high-risk groups such as elderly or immunocompromised patients, the incidence of zoster can be as high as 50%. Radiation oncologists are likely to see zoster because cancer, and cancer therapy, can adversely affect immune function. A few reports suggest that radiation therapy is a risk factor for zoster, and that the skin eruption is often in or near the radiation treatment field. The diagnosis is typically made through clinical history and exam, but several tests are available to confirm the diagnosis and differentiate it from other infections or dermatitis. Effective management consists of prompt antiviral medication, acute pain control, appropriate precautions to limit transmission, and referral to specialists in certain cases. Despite appropriate therapy, up to 18% of patients can develop persistent postherpetic neuralgia, defined as pain more than 4 months after resolution of the rash. Several classes of pain medication are available to treat acute or long-term pain. Vaccination against zoster is recommended for patients aged 60 years or older, as it can reduce the incidence and severity of zoster.

Systemic varicella zoster virus reactive effector memory T-cells impaired in the elderly and in kidney transplant recipients

Varicella zoster virus (VZV) infections cause varicella and subsequently herpes zoster upon reactivation. Immune-compromised individuals and the elderly are at high risk of developing herpes zoster due to waning of VZV-specific T-cell immunity. In the present study, a novel functional T-cell assay was developed to test the correlation between age and VZV-specific T-cell responses in peripheral blood from healthy individuals. Secondly, VZV-specific T-cell responses from renal transplant recipients were compared with healthy individuals. Monocytes were differentiated into mature monocyte-derived dendritic cells (moDCs) and were infected with VZV. T-cells were co-cultured with autologous moDCs infected with VZV and subjected to flowcytometric analysis to identify the phenotype (i.e., naïve [NA: CCR7(+) CD45RO(-) ], central [CM: CCR7(+) CD45RO(+) ] and effector memory [EM: CCR7(-) CD45RO(+) ] T-cells) and the frequency of VZV-reactive T-cell subsets by intra-cellular IFN-γ flowcytometry. In contrast to NA and CM T-cells, the frequency of VZV-reactive CD4 and CD8 EM T-cells was inversely correlated with age (P = 0.0007 and P = 0.01). No difference was found in the percentage of VZV-reactive CD4 NA, CM and EM T-cells between transplant recipients and controls. However, the percentage of VZV-reactive CD8 EM T-cells was significantly lower in transplant recipients compared to controls (P = 0.02). In conclusion, moDCs infected with VZV are efficient antigen presenting cells applicable to enumerate and characterize the phenotype and differentiation status of the systemic VZV-specific T-cell response ex-vivo. The data suggest that VZV-reactive EM T-cells are impaired in the elderly and renal transplant recipients.

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

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

Varicella zoster vaccines and their implications for development of HSV vaccines

Live attenuated vaccines to prevent varicella and zoster have been available in the US for the past 17 years, with a resultant dramatic decrease in varicella incidence and a predicted future decrease in the incidence of zoster. The pathogenesis and immune responses to varicella zoster virus (VZV) as well as the safety and effectiveness of VZV vaccines are reviewed. The lack of sterilizing immunity provided by VZV vaccines has not prevented them from being safe and effective. Virological and pathological information concerning parallels and differences between VZV and herpes simplex virus (HSV) are highlighted. Although VZV and HSV are distinct pathogens, they appear to have similarities in target organs and immunity that provide an expectation of a high likelihood for the success of vaccination against HSV, and predicted to be similar to that of VZV.

Incidence and use of resources for chickenpox and herpes zoster in Latin America and the Caribbean--a systematic review and meta-analysis

BACKGROUND

Varicella-zoster virus causes chickenpox and herpes zoster. More than 90% of varicella cases occur in childhood. The aim of this study was to gather all relevant information on epidemiology and resource use in Latin America and the Caribbean since 2000.

METHODS

Epidemiologic studies published since 2000 with at least 50 cases of varicella or herpes zoster, or at least 10 cases of congenital disease were included. Gray literature was also searched. Outcomes included incidence, admission rate, mortality and case-fatality ratio. Use of resources and both direct and indirect costs associated were extracted.

RESULTS

From the 495 records identified, 23 were included in the meta-analysis to report varicella-zoster virus outcomes and 3 in the herpes zoster analysis. The global pooled varicella incidence in subjects under 15 years of age was 42.9 cases per 1000 individuals per year (95% confidence interval: 26.9-58.9); children under 5 years of age were the most affected. Pooled general admission rate was 3.5 per 100,000 population (95% confidence interval: 2.9-4.1) and median hospitalization was 5-9 days. The most common varicella complications reported in studies were skin infections (3-61%), followed by respiratory infections (0-15%) and neurologic problems (1-5%). Direct costs averaged (2011/international dollar [I$]) $2040 per admission (range, I$ 298-5369) and I$70 per clinical visit (range, 11-188 I$).

CONCLUSIONS

Limited information was available on the outcomes studied. Improvements in the surveillance of ambulatory cases are required to obtain a better epidemiologic picture. As of 2011, only 2 countries introduced the vaccine in national immunization programs in Latin America and the Caribbean.

Herpes zoster ophthalmicus in an otherwise healthy 2-year-old child

The following report describes a previously healthy 2-year-old girl with herpes zoster ophthalmicus (HZO). The child presented with a painless vesicular skin eruption covering the left forehead. There was only a history of household exposure to varicella zoster virus (VZV) and the child had not been vaccinated against VZV. PCR assays on vesicular fluid identified VZV DNA. Treatment with acyclovir was started early in the clinical course. In addition, the girl was treated with locally administered ophthalmological acyclovir ointment. Besides some dermal excoriations, a complete resolution of the HZO was achieved without sequelae.

Varicella-zoster virus: Prevention through vaccination

Widespread use of varicella vaccine in the United States has drastically changed the epidemiology of the disease. Although chickenpox is no longer a ubiquitous childhood infection, varicella-zoster virus continues to circulate in the community and nonimmune pregnant women remain at risk. Varicella can cause severe infection in pregnant women, often complicated by viral pneumonia. Maternal varicella occurring in the first half of pregnancy can cause the rare but devastating congenital varicella syndrome, whereas infection in the late stages of pregnancy may cause neonatal varicella. The best approach to avoiding the morbidity and mortality associated with chickenpox in pregnancy is to screen and vaccinate susceptible reproductive-age women.

Immunogenicity and safety of two tetravalent (measles, mumps, rubella, varicella) vaccines coadministered with hepatitis a and pneumococcal conjugate vaccines to children twelve to fourteen months of age

BACKGROUND

This study compared single-dose tetravalent measles, mumps, rubella, varicella vaccine, Priorix-Tetra, stored refrigerated (GSK+4C) or frozen (GSK-20C), with ProQuad (Merck-20C), when coadministered with hepatitis A vaccine (HAV) and 7-valent pneumococcal conjugate vaccine (PCV7).

METHODS

Multicenter, observer-blind phase 2 study in 1783 healthy 12-14 month olds randomized to: GSK+4C (n = 705), GSK-20C (n = 689) or Merck-20C (n = 389), administered concomitantly with HAV (Havrix) and PCV7 (Prevnar). Seroresponse rates and antibody geometric mean concentrations/titers were determined from enzyme-linked immunosorbent assay and neutralization assays. Reactogenicity and safety were assessed.

RESULTS

Seroresponse rates (day 42) were >97% for measles and rubella viruses and >92% for mumps virus, in all groups. Noninferiority of both GSK+4C and GSK-20C vaccines versus Merck-20C was demonstrated for seroresponse rates to measles, mumps and rubella viruses (lower 97.5% confidence interval above -5%, -10% and -5%, respectively). For varicella-zoster virus, seroresponse rates were 57.1%, 69.8% and 86.7% in the GSK+4C, GSK-20C and Merck-20C groups, respectively. Noninferiority was not shown for either GSK vaccine (lower 97.5% confidence intervals <-15%). Geometric mean concentration ratios for anti-varicella-zoster virus demonstrated noninferiority (lower 97.5% confidence interval ≥ 0.5) versus Merck-20C for GSK-20C only. Geometric mean concentration ratios for antibodies to HAV and to PCV7 pneumococcal serotypes also met criteria for noninferiority for both GSK groups compared with Merck-20C. GSK vaccine safety was observed comparable to Merck-20C. Localized but not generalized measles/rubella-like rash and grade 3 fever was reported slightly more frequently with GSK vaccines, but antipyretic use was similar. The incidence of subjects experiencing at least 1 serious adverse event was 2.0%, 2.9% and 1.8% in the GSK+4C, GSK-20C and Merck-20C groups, respectively.

CONCLUSIONS

Noninferiority of both GSK measles, mumps, rubella, varicella vaccines versus Merck-20C was demonstrated for responses to measles, mumps and rubella viruses but was not fully demonstrated for varicella-zoster virus. The vaccines showed acceptable reactogenicity/safety when coadministered with HAV and PCV7.

Management and control of varicella on cruise ships: a collaborative approach to promoting public health

BACKGROUND

In most years varicella is the vaccine-preventable disease most frequently reported to Centers for Disease Control and Prevention (CDC) by cruise ships. Since 2005, CDC has received numerous isolated case reports of varicella among crew members and has investigated varicella outbreaks aboard vessels sailing into and from US seaports.

METHODS

CDC investigators reviewed electronic varicella case reports from 2005 to 2009 and outbreak reports from 2009 to characterize the response and control efforts implemented by cruise ships in accordance with CDC protocols. Outbreak reports from 2009 were manually reviewed for details of case identification, contact investigations, isolation and restriction of cases and contacts, respectively, and number of contacts administered varicella vaccine post-exposure by cruise lines.

RESULTS

During 2005 to 2009, cruise ships reported 278 cases of varicella to CDC among predominantly male (80%) crew members, three-quarters of whom were residents of Caribbean countries, Indonesia, the Philippines, or India, and whose median age was 29 years. Cases were more commonly reported during spring and winter months. During 2009, cruise ships reported 94 varicella cases among crew members of which 66 (70%) were associated with 18 reported varicella outbreaks. Outbreak response included isolation of 66 (100%) of 66 cases, restriction of 66 (26%) of 255 crew-contacts, and administration of post-exposure vaccine to 522 close contacts and other susceptible crew members per standard CDC recommendations.

DISCUSSION

Most cases reported to CDC during 2005 to 2009 were among non-US resident crew members. Overall, cruise lines sailing into North America have the onboard capability to manage varicella cases and outbreaks and appear responsive to CDC recommendations. Cruise lines should continue to implement CDC-recommended response protocols to curtail outbreaks rapidly and should consider whether pre-placement varicella immunity screening and vaccination of crew members is a cost-effective option for their respective fleet operations.

Antibody persistence for 3 years following two doses of tetravalent measles-mumps-rubella-varicella vaccine in healthy children

Two doses of a varicella-containing vaccine in healthy children <12 years are suggested to induce better protection than a single dose. Persistence of immunity against measles, mumps, rubella, and varicella as well as varicella breakthrough cases were assessed 3 years after two-dose measles, mumps, rubella, and varicella (MMRV) vaccination or concomitant MMR (Priorix™) and varicella (Varilrix™) vaccination. Four hundred ninety-four healthy children, 12-18 months old at the time of the first dose, received either two doses of MMRV vaccine (GlaxoSmithKline Biologicals) 42-56 days apart (MMRV, N = 371) or one dose of MMR and varicella vaccines administered simultaneously at separate sites, followed by another MMR vaccination 42-56 days later (MMR + V, N = 123). Three hundred-four subjects participated in 3-year follow-up for persistence of immunity and occurrence of breakthrough varicella (MMRV, N = 225; MMR + V, N = 79). Antibodies were measured by ELISA (measles, mumps, rubella) and immunofluorescence (varicella). Contacts with individuals with varicella or zoster and cases of breakthrough varicella disease were recorded. Three years post-vaccination seropositivity rates in subjects seronegative before vaccination were: MMRV-measles, 98.5% (geometric mean titer [GMT] = 3,599.6); mumps, 97.4% (GMT = 1,754.5); rubella, 100% (GMT = 51.9); varicella, 99.4% (GMT = 225.5); MMR + V-measles, 97.0% (GMT = 1,818.8); mumps, 93.8% (GMT = 1,454.6); rubella, 100% (GMT = 53.8); and varicella, 96.8% (GMT = 105.8). Of the subjects, 15-20% reported contact with individuals with varicella/zoster each year. After 3 years, the cumulative varicella breakthrough disease rate was 0.7% (two cases) in the MMRV group and 5.4% (five cases) in the MMR + V group.

CONCLUSION

Immunogenicity of the combined MMRV vaccine was sustained 3 years post-vaccination. (208136/041/NCT00406211).

Novel genetic variation identified at fixed loci in ORF62 of the Oka varicella vaccine and in a case of vaccine-associated herpes zoster

The live attenuated Oka varicella vaccine (vOka), derived from clade 2 wild-type (wt) virus pOka, is used for routine childhood immunization in several countries, including the United States, which has caused dramatic declines in the incidence of varicella. vOka can cause varicella, establish latency, and reactivate to cause herpes zoster (HZ). Three loci in varicella-zoster virus (VZV) open reading frame 62 (ORF62) (106262, 107252, and 108111) are used to distinguish vOka from wt VZV. A fourth position (105705) is also fixed for the vOka allele in nearly all vaccine batches. These 4 positions and two vOka mutations (106710 and 107599) reportedly absent from Varivax were analyzed on Varivax-derived ORF62 TOPO TA clones. The wt allele was detected at positions 105705 and 107252 on 3% and 2% of clones, respectively, but was absent at positions 106262 and 108111. Position 106710 was fixed for the wt allele, whereas the vOka allele was present on 18.4% of clones at position 107599. We also evaluated the 4 vOka markers in an isolate obtained from a case of vaccine-caused HZ. The isolate carried the vOka allele at positions 105705, 106262, and 108111. However, at position 107252, the wt allele was present. Thus, all of the ORF62 vOka markers previously regarded as fixed occur as the wt allele in a small percentage of vOka strains. Characterization of all four vOka markers in ORF62 and of the clade 2 subtype marker in ORF38 is now necessary to confirm vOka adverse events.

The controversy of varicella vaccination in children with acute lymphoblastic leukemia

BACKGROUND

The available guidelines for varicella vaccination of susceptible children with acute lymphoblastic leukemia (ALL) have become increasingly conservative. However, vaccination of those who have remained in continuous complete remission for 1 year and are receiving chemotherapy is still considered a reasonable option. There is little available data to allow a comparison of the risk versus benefit of vaccinating these patients.

PROCEDURE

We retrospectively reviewed mortality due to varicella in the records of 15 pediatric ALL study groups throughout Europe, Asia, and North America during the period 1984-2008.

RESULTS

We found that 20 of 35,128 children with ALL (0.057%; 95% confidence interval [CI], 0.037-0.088%) died of VZV infection. The mortality rate was lower in North America (3 of 11,558 children, 0.026%; 95% CI, 0.009-0.076%) than in the Asian countries (2 of 4,882 children, 0.041%; 95% CI, 0.011-0.149%) and in Europe (15 of 18,688 children, 0.080%; 95% CI, 0.049-0.132%) consistent with the generally higher rate of VZV vaccination in North America. Fourteen of the 20 patients (70%) died during the first year of treatment for ALL. One death was attributed to varicella vaccination.

CONCLUSIONS

The negligible rate of fatal varicella infection in children with ALL, the risk that accompanies vaccination, and the necessity of withholding chemotherapy for vaccination appear to outweigh the potential benefit of varicella vaccination for children during treatment of ALL.

Epidemiological characteristics of varicella from 2000 to 2008 and the impact of nationwide immunization in Taiwan

Background

Varicella has an important impact on public health. Starting in 2004 in Taiwan, nationwide free varicella vaccinations were given to 1-year-old children.

Methods

Our study investigated the epidemiological characteristics of varicella from 2000 to 2008, and assessed the change of varicella epidemiology after the mass varicella immunization. ICD-9-CM codes related to varicella or chickenpox (052, 052.1, 052.2, 052.7, 052.8, 052.9) were analyzed for all young people under 20 years of age through the National Health Insurance database of Taiwan from 2000 to 2008.

Results

Case numbers of varicella or chickenpox significantly declined after the nationwide immunization in 2004. Winter, particularly January, was the epidemic season of varicella. We found a significant post-vaccination decrease in incidence among preschool children, especially 3 to 6 year-old children-- the peak incidence was 66 per thousand for 4 and 5 year-old children before the nationwide immunization (2000 to 2003), and the peak incidence was 23 per thousand for 6 year-old children in 2008 (p < 0.001). Varicella-related hospitalization also significantly decreased in children younger than 6 years after the nationwide immunization.

Conclusion

The varicella annual incidence and varicella-related hospitalization markedly declined in preschool children after nationwide varicella immunization in 2004.

Cardiac-related varicella mortality in childhood: a literature review with clinical experience

Among unvaccinated populations, primary varicella zoster virus (VZV) infection results in a minor childhood illness for the majority of individuals. Mortality is rare, and fatalities associated with cardiac complications are exceptional. In a population where routine VZV vaccination is not practised, we report a death in a previously healthy child secondary to VZV myocarditis. A literature review of cardiac-related VZV mortality in childhood is included. This identified a further 13 cases where death was associated with or attributable to, direct involvement of the myocardium or conducting system with what is frequently considered a benign childhood illness.

The cost-effectiveness of varicella and combined varicella and herpes zoster vaccination programmes in the United Kingdom

BACKGROUND

Despite the existence of varicella vaccine, many developed countries have not introduced it into their national schedules, partly because of concerns about whether herpes zoster (HZ, shingles) will increase due to a lack of exogenous boosting. The magnitude of any increase in zoster that might occur is dependent on rates at which adults and children mix - something that has only recently been quantified - and could be reduced by simultaneously vaccinating older individuals against shingles. This study is the first to assess the cost-effectiveness of combined varicella and zoster vaccination options and compare this to alternative programmes.

METHODS AND FINDINGS

The cost-effectiveness of various options for the use of varicella-zoster virus (VZV) containing vaccines was explored using a transmission dynamic model. Underlying contact rates are estimated from a contemporary survey of social mixing patterns, and uncertainty in these derived from bootstrapping the original sample. The model was calibrated to UK data on varicella and zoster incidence. Other parameters were taken from the literature. UK guidance on perspective and discount rates were followed. The results of the incremental cost-effectiveness analysis suggest that a combined policy is cost-effective. However, the cost-effectiveness of this policy (and indeed the childhood two-dose policy) is influenced by projected benefits that accrue many decades (80-100 years or more) after the start of vaccination. If the programme is evaluated over shorter time frames, then it would be unlikely to be deemed cost-effective, and may result in declines in population health, due to a projected rise in the incidence of HZ. The findings are also sensitive to a number of parameters that are inaccurately quantified, such as the risk of HZ in varicella vaccine responders.

CONCLUSIONS

Policy makers should be aware of the potential negative benefits in the first 30-50 years after introduction of a childhood varicella vaccine. This can only be partly mitigated by the introduction of a herpes zoster vaccine. They have to decide how they value the potential benefits beyond this time to consider childhood vaccination cost effective.

The burden of varicella from a parent's perspective and its societal impact in The Netherlands: an Internet survey

BACKGROUND

Varicella is a common childhood disease. Only 5% of first varicella-zoster-virus infections occur asymptomatically. Most data on the burden of varicella stem from health service databases. This study aims to provide insight in the burden of varicella from a parent's perspective including cases outside the healthcare system.

METHODS

An internet questionnaire was developed for parents in the Netherlands to report health care resource use and productivity losses during the varicella episode in their child younger than 6 years. 11,367 invitations were sent out to members with children of an internet panel of a market research agency. 4,168 (37%) parents started the questionnaire (response rate), of which 360 (9%) stopped before completion and 1,838 (44%) were out of the target group. In total 1,970 parents completed the questionnaire. The questionnaire provided a symptom list ranging from common symptoms, such as skin vesicles, itching to fits or convulsions. A posteriori, in the analyses, the symptoms 'skin infections', 'fits/convulsions', 'unconsciousness', and 'balance and movement disorders' were labelled as complications. There was no restriction to time since the varicella episode for inclusion in the analyses.

RESULTS

The 1,970 respondents had in total 2,899 children aged younger than six years, of which 2,564 (88%) children had had varicella. In 62% of the episodes the parent did not seek medical help. In 18% of all episodes symptoms labelled as complications were reported; in 11% of all episodes parents visited a medical doctor (MD) for a complication. Reporting of complications did not differ (X2 ; p = 0.964) between children with a recent (≤ 12 months ago) or a more distant (> 12 months) history of varicella. Prescription drugs were used in 12% of the children with varicella; OTC drugs in 72%. Parents reported work loss in 17% of the varicella-episodes (23% when MD visit; 14% when no MD-visit) for on average 14 hours, which equals to 2.5 hours of work loss for any given varicella-episode.

CONCLUSIONS

This study shows the full spectrum of varicella-episodes and associated healthcare use, including the large proportion of cases not seeking medical care and the societal impact associated with those cases.

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

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

Effectiveness of state-level vaccination mandates: evidence from the varicella vaccine

This paper utilizes longitudinal data on varicella (chickenpox) immunizations in order to estimate the causal effects of state-level school-entry and daycare-entry immunization mandates within the United States. We find significant causal effects of mandates upon vaccination rates among preschool children aged 19-35 months; these effects appear in the year of mandate adoption, peak two years after adoption, and show a minimal difference from the aggregate trend about six years after adoption. For a mandate enacted in 2000, the model and estimates imply that roughly 20% of the short-run increase in state-level immunization rates was caused by the mandate introduction. We find no evidence of differential effects for different socioeconomic groups. Combined with previous cost-benefit analyses of the varicella vaccine, the estimates suggest that state-level mandates have been effective from an economic standpoint.

Molecular studies of the Oka varicella vaccine

Varicella zoster virus (VZV) is one of eight members of the Herpesviridae family for which humans are the primary host; it causes two distinct diseases, varicella (chickenpox) and zoster (shingles). Varicella results from primary infection, during which the virus establishes latency in sensory neurons, a characteristic of all members of the Alphaherpesvirinae subfamily. Zoster is caused by reactivation of latent virus, which typically occurs when cellular immunity is impaired. VZV is the first human herpesvirus for which a vaccine has been licensed. The vaccine preparation, v-Oka, is a live-attenuated virus stock produced by the classic method of tissue culture passage in animal and human cell lines. Over 90 million doses of the vaccine have been administered in countries worldwide, including the USA, where varicella morbidity and mortality has declined dramatically. Over the last decade, several laboratories have been committed to investigating the mechanism by which the Oka vaccine is attenuated. Mutations have accumulated across the genome of the vaccine during the attenuation process; however, studies of the contribution of these changes to vaccine attenuation have been hampered by the lack of a suitable animal model of VZV disease and by the heterogeneity that exists among the viral population within the vaccine preparation. Notwithstanding, a wealth of data has been generated using various laboratory methodologies. Studies of the vaccine virus in human xenografts implanted in severe combined immunodeficiency-hu mice, have enabled analyses of the replication dynamics of the vaccine in dorsal root ganglia, T lymphocytes and skin. In vitro assays have been used to investigate the effect of vaccine mutations on viral gene expression and sequence analysis of vaccine rash viruses has permitted investigations into spread of the vaccine virus in a human host. We present here a review of what has been learned thus far about the molecular and phenotypic characteristics of the Oka vaccine.

Update on available vaccines in India: report of the APPA VU 2010: I

The Asia Pacific Pediatric Association Vaccinology Update 2010 was held in Mumbai on November 13-14, 2010 to discuss the latest information on burden of infectious diseases, recent developments in vaccines and their impact on immunization practices against infectious diseases occurring in Indian children. During the conference the importance of including conjugate Haemophilus influenzae type b vaccine and anti-rabies vaccines in routine immunization was stressed. Also, the need for giving a second dose of measles mumps rubella vaccine at school entry; and the need for a two-dose varicella vaccine regimen (first dose at 12-15 months of age and a second dose at age 4-6 years) was elucidated. Information related to vaccines which have become available in India in recent years, namely, inactivated poliovirus vaccine; diphtheria, tetanus, acellular pertussis (DTaP) vaccine; conjugate pneumococcal vaccine; rotavirus vaccines; H1N1 vaccines; live attenuated hepatitis A virus vaccine; oral cholera vaccine; tetanus, reduced-dose diphtheria, acellular pertussis (Tdap) vaccine; and human papillomavirus vaccines were discussed.

Varicella rates among unvaccinated and one-dose vaccinated healthy children in Izmir, Turkey

OBJECTIVES

We aimed to determine the rate of breakthrough varicella in Turkey, a country with low varicella vaccination coverage.

METHODS

This study was conducted between April 2008 and March 2009 at the Well-Child Clinic at Ege University and pediatricians' offices. We collected information on vaccination status and varicella infection using a questionnaire. In order to elicit more details about the severity of illness, we interviewed all parents and reviewed the clinician records. Vaccination status was verified from the medical records or vaccination cards with dates.

RESULTS

A total of 2802 children were evaluated. Of these, 1683 had been vaccinated with a single dose of varicella vaccine and 1119 were unvaccinated. Among vaccinated children, 466 (27.7%) had breakthrough varicella. Vaccinated children tended to have mild varicella. However, about 25% of breakthrough cases had moderate or severe disease. Children who were vaccinated ≥ 5 years previously had a 3.7-fold higher risk of breakthrough disease than those who were vaccinated <5 years before. Vaccination at younger than 15 months of age was not significantly associated with an increased risk of breakthrough infection.

CONCLUSIONS

Breakthrough varicella is not rare in Turkey where varicella infections are common. A longer interval since vaccination may be a risk factor for developing breakthrough varicella. Children who had been vaccinated >5 years previously were at risk for breakthrough disease. A two-dose varicella vaccine policy may be needed to provide improved protection.

Complete atrioventricular block as a complication of varicella in children

Although varicella is a benign and self-limited disease in children, serious complications can occur. We herein report a case of a 15-month-old boy who required a permanent pacemaker because of complete atrioventricular block as a complication of varicella. Universal vaccination is warranted to prevent such a potentially fatal complication in Japan where varicella is still endemic.

[Risk of vaccination in children with epilepsy]

INTRODUCTION

The central nervous system, previously considered as "immune privileged", does exhibit features of inflammation in response to injury, infection or disease. We do not know its reactions on immunization. We do not know how common febrile seizures after vaccination are and if there are subgroups of children at higher risk. What is the long term outcome for children who had afebrile seizure after vaccination? Can the vaccine be a direct cause of a condition called an epileptic encephalopathy, where seizures damage the brain with the resulting epilepsy?

DISCUSSION AND CONCLUSION

It should not be forgotten that "benign infective childhood diseases" can, and do, kill, and that vaccines are a public health intervention saving many millions of lives around the world. Parents as well as doctors have fear: whether vaccinations can cause convulsions, epilepsy or encephalopathy. Large studies of this issue have produced conflicting results, although the recent consensus is that the risk of vaccine-induced epilepsy and or encephalopathy, if it exists at all, is extremely low. It is necessary to establish a proposed immunization program for children at neurologically high risk and for children with epilepsy to protect them and the whole population from infectious diseases, children from immunization adverse events, and avoid possibilities of legal trial. It is necessary to know everything about the risks and benefits of immunizations for each child. For each child, the risks of the disease, and its squeal, must be compared with the vaccine's protective efficacy and potential adverse reactions. Vaccination is given preference in nearly all children with epilepsy.