Universal Varicella Immunization Research Articles

A systematic review of varicella seroprevalence in European countries before universal childhood immunization: deriving incidence from seroprevalence data.

Surveillance systems for varicella in Europe are highly heterogeneous or completely absent. We estimated the varicella incidence based on seroprevalence data, as these data are largely available and not biased by under-reporting or underascertainment. We conducted a systematic literature search for varicella serological data in Europe prior to introduction of universal varicella immunization. Age-specific serological data were pooled by country and serological profiles estimated using the catalytic model with piecewise constant force of infection. From the estimated profiles, we derived the annual incidence of varicella infection (/100·000) for six age groups (<5, 5-9, 10-14, 15-19, 20-39 and 40-65 years). In total, 43 studies from 16 countries were identified. By the age of 15 years, over 90% of the population has been infected by varicella in all countries except for Greece (86·6%) and Italy (85·3%). Substantial variability across countries exists in the age-specific annual incidence of varicella primary infection among the <5 years old (from 7052 to 16 122 per 100 000) and 5-9 years old (from 3292 to 11 798 per 100 000). The apparent validity and robustness of our estimates highlight the importance of serological data for the characterization of varicella epidemiology, even in the absence of sampling or assay standardization.

A national register-based study of paediatric varicella hospitalizations in Denmark 2010-2016.

Varicella, usually a mild disease of childhood, can also cause complications and hospitalization. Universal varicella immunization is implemented in several countries worldwide, but not in Denmark. Taking advantage of unique national registers, we aimed to estimate the incidence of paediatric varicella hospitalizations and assess determinants for hospitalization. For this purpose, we designed a nationwide, retrospective register study of paediatric varicella hospitalizations and applied a case-cohort design and logistic regression analysis comparing hospitalized varicella patients to a sample of the entire paediatric population in Denmark. Varicella patients were identified in The Danish National Patient Register and referents were randomly selected from the Danish Civil Registration System. The incidence of paediatric varicella admissions was 11/100 000 children 0-18 years of age/year. Of admitted children 67·1% had complications and 30·0% had underlying disease. All categories of underlying disease significantly increased the odds of hospitalization as well as male gender and not having been born in Denmark. In conclusion, we found a considerable burden of paediatric varicella disease in Danish hospitals, of similar magnitude as in other European countries comparable to Denmark. With this study we have provided epidemiological data needed for considering implementation of varicella vaccine in Denmark.

Estimation of the burden of varicella in Europe before the introduction of universal childhood immunization

BackgroundVaricella is generally considered a mild disease. Disease burden is not well known and country-level estimation is challenging. As varicella disease is not notifiable, notification criteria and rates vary between countries. In general, existing surveillance systems do not capture cases that do not seek medical care, and most are affected by underreporting and underascertainment. We aimed to estimate the overall varicella disease burden in Europe to provide critical information to support decision-making regarding varicella vaccination.MethodsWe conducted a systematic literature review to identify all available epidemiological data on varicella IgG antibody seroprevalence, primary care and hospitalisation incidence, and mortality. We then developed methods to estimate age-specific varicella incidence and annual number of cases by different levels of severity (cases in the community, health care seekers in primary care and hospitals, and deaths) for all countries belonging to the European Medicines Agency (EMA) region and Switzerland.ResultsIn the absence of universal varicella immunization, the burden of varicella would be substantial with a total of 5.5 million (95% CI: 4.7–6.4) varicella cases occurring annually across Europe. Variation exists between countries but overall the majority of cases (3 million; 95% CI: 2.7–3.3) would occur in children <5 years. Annually, 3–3.9 million patients would consult a primary care physician, 18,200–23,500 patients would be hospitalised, and 80 varicella-related deaths would occur (95% CI: 19–822).ConclusionsVaricella disease burden is substantial. Most cases occur in children <5 years old but adults require hospitalisation more often and are at higher risk of death. This information should be considered when planning and evaluating varicella control strategies. A better understanding of the driving factors of country-specific differences in varicella transmission and health care utilization is needed. Improving and standardizing varicella surveillance in Europe, as initiated by the European Centre for Disease Prevention and Control (ECDC), is important to improve data quality to facilitate inter-country comparison.

Time trends in pediatric Herpes zoster hospitalization rate after Varicella immunization

Herpes zoster (HZ) is an emerging concern for public health officials. The aim of this study was to determine whether universal Varicella immunization implemented in 2004 had an impact on HZ hospitalization in immunocompetent children in Greece. All HZ hospitalizations were recorded during the period 1999-2011. The overall attributable hospitalization rate was 13.89 cases/1000 hospital admissions (95%CI: 11.69-16.38 cases/1000 hospital admissions). HZ hospitalization rate remained unchanged during the study period. These data provide a basis for monitoring HZ hospitalization rate among children following universal toddler immunization.

Application of Oral Fluid Assays in Support of Mumps, Rubella and Varicella Control Programs.

Detection of specific viral antibody or nucleic acid produced by infection or immunization, using oral fluid samples, offers increased potential for wider population uptake compared to blood sampling. This methodology is well established for the control of HIV and measles infections, but can also be applied to the control of other vaccine preventable infections, and this review describes the application of oral fluid assays in support of mumps, rubella and varicella national immunization programs. In England and Wales individuals with suspected mumps or rubella, based on clinical presentation, can have an oral fluid swab sample taken for case confirmation. Universal varicella immunization of children has led to a drastic reduction of chickenpox in those countries where it is used; however, in England and Wales such a policy has not been instigated. Consequently, in England and Wales most children have had chickenpox by age 10 years; however, small, but significant, numbers of adults remain susceptible. Targeted varicella zoster virus (VZV) immunization of susceptible adolescents offers the potential to reduce the pool of susceptible adults and oral fluid determination of VZV immunity in adolescents is a potential means of identifying susceptible individuals in need of VZV vaccination. The main application of oral fluid testing is in those circumstances where blood sampling is deemed not necessary, or is undesirable, and when the documented sensitivity and specificity of the oral fluid assay methodology to be used is considered sufficient for the purpose intended.

Time Trends in Pediatric Hospitalizations for Varicella Infection Are Associated with Climatic Changes: A 22-Year Retrospective Study in a Tertiary Greek Referral Center

Background/AimsThe transmission rate of air-borne infectious diseases may vary secondary to climate conditions. The study assessed time trends in the seasonality of hospitalized varicella cases in a temperate region in relation to climatic parameters prior to the implementation of universal varicella immunization.MethodsA retrospective descriptive study was conducted among all pediatric and adolescent varicella patients (n = 2366) hospitalized at the “Aghia Sophia” Children's Hospital during 1982–2003 in Athens, Greece. Date of infection was computed based on hospital admission date. Seasonal and monthly trends in the epidemiology of varicella infection were assessed with time series analysis (ARIMA modeling procedure). The correlation between the frequency of varicella patients and the meteorological parameters was examined by the application of Generalized Linear Models with Gamma distribution.ResultsDuring 1982–2003, the occurrence of hospitalized varicella cases increased during summer (p = 0.025) and decreased during autumn (p = 0.021), and particularly in September (p = 0.003). The frequency of hospitalized varicella cases was inversely associated with air temperature (p<0.001). In contrast, the occurrence of hospitalized varicella cases was positively associated with wind speed (p = 0.009).ConclusionsPediatric hospitalizations for varicella infection rates have increased during summer and decreased during autumn in the examined temperate region. Time trends in hospitalized varicella cases are associated with climatic variables.

The epidemiology of chickenpox in UK 5-year olds: An analysis to inform vaccine policy

Varicella vaccine is not routinely administered to children in many countries including the UK. Longitudinal data are lacking to inform optimal schedules. We report the prevalence of VZV infection at 5 years of age, cumulative incidence between 3 and 5 years and socio-demographic associations with risk of infection using longitudinal data on 12,509 children from the UK Millennium Cohort Study. VZV prevalence by 5 years was 76.9% [95% CI: 75.9%, 78.0%]. The cumulative incidence between 3 and 5 years was 32.2% [95% CI: 31.1%, 33.3%]. Risk of infection by 5 years was associated with higher maternal socio-economic status, larger household size and formal day-care attendance at 9 months and 3 years. If universal varicella immunisation were introduced in the UK, where 40% children have attended some formal day-care by 3 years, a schedule commencing early in the second year of life would be indicated.

Commentary: The Case for Universal Varicella Immunization

The article in this month’s issue on immunity to the varicella-zoster virus (VZV) in France highlights the fact that varicella is primarily a childhood disease and that prevention of varicella and its attendant morbidity and mortality require the universal vaccination of children. Yet despite the availability of a safe and effective vaccine, many countries in Europe and the industrialized world, at present, have not included varicella vaccine in their routine immunization programs. 1 Considered by many physicians to be a benign disease, varicella can result in serious complications, sequelae and death. In the United States, before use of varicella vaccine, there were an average of 4 million cases of varicella that resulted in 10,500 –15,000 hospitalizations and 100 –150 deaths every year. 2– 6 Although the risk of severe disease was higher in adults, children bore the brunt of the health burden with 90% of varicella cases, 67% of the varicella hospitalizations and one-half the varicella deaths occurring in this age group. 2– 4 It was recognition of this health burden and the knowledge that children were the primary transmitters of infection that led the United States to adopt a program of universal vaccination of children in 1995. Germany is the only country in Europe with routine childhood immunization. Varicella vaccine was incorporated into the routine immunization schedule in July 2004, as a

Declining incidence of chickenpox in the absence of universal childhood immunisation

Objective: To examine the epidemiology of chickenpox in Wales from 1986 to 2001. Design: Descriptive analysis of chickenpox consultations reported by the Welsh general practice sentinel surveillance scheme for infectious...

Canada's first universal varicella immunization program: Lessons from Prince Edward Island.

A live attenuated varicella vaccine was licensed in Canada in December 1998. The first universal varicella immunization program in Canada was initiated in Prince Edward Island in 2000. Students in grades one to six without a history of varicella were offered the vaccine, administered by Public Health Nurses, in school clinics during February and March 2000. The acceptance rate ranged from 29.1% of all grade one students to 9.8% of all grade six students; overall, 18.8% of students received the vaccine. A universal program for children 12 months of age was introduced on April 1, 2000 and catch-up clinics for those between 12 months of age and those in grade one were introduced in June 2000. Repeated media announcements and the cooperation of staff in schools and daycare facilities assisted in informing parents about the availability of the vaccine. Vaccine-associated adverse events have been uncommon and the vaccine has been well accepted.

Reservations about universal varicella immunisation in the US

Reservations about universal varicella immunisation in the US

Reservations about universal varicella immunisation in the US

Reservations about universal varicella immunisation in the US

Reactions of pediatricians to the recommendation for universal varicella vaccination.

To determine the rate of self-reported adherence by pediatricians to the 1995 American Academy of Pediatrics and the Advisory Committee on Immunization Practices varicella immunization recommendations and to evaluate factors that might influence adherence. Mail survey. Washington State pediatricians. Logistic regression was used to identify demographic characteristics, attitudes about varicella vaccine, and previous experiences with the disease that were associated with self-reported adherence to universal varicella immunization recommendations. Completed surveys were returned by 76% of contacted pediatricians, of whom 42% reported following a policy of universal varicella immunization. In multivariate analysis, agreement with statements regarding the effectiveness of varicella vaccine in reducing rare but serious complications of the disease (odds ratio [OR], 4.90; 95% confidence interval [CI], 2.30-10.50) and in decreasing work loss by parents (OR, 4.21; 95% CI, 1.14-15.50) were associated with recommending universal immunization. Disagreement with statements concerning the lack of the need for varicella immunization because complications are rare (OR, 2.54; 95% CI, 1.12-5.74), it is not required for school entry (OR, 2.52; 95% CI, 1.37-4.64), and it is not medically cost-effective (OR, 2.25; 95% CI, 1.21-4.18) were also associated with universally recommending the vaccine. In addition, experience with varicella encephalitis was also associated with adherence to the recommendations (OR, 1.96; 95% CI, 1.06-3.65). Conversely, those who were concerned that varicella vaccine might not provide lifelong immunity were less likely to report recommending universal vaccination (OR, 0.36; 95% CI, 0.19-0.68). Fewer than 50% of responding Washington State pediatricians reported recommending universal varicella vaccination. Adherence to the recommendations appears to be influenced by personal experience, perceptions about the potential seriousness of varicella, and beliefs about the societal and medical cost-effectiveness of varicella vaccine.

Concerns regarding universal varicella immunization. Time will tell.

The American Academy of Pediatrics, the Advisory Committee on Immunization Practices, and the American Academy of Family Physicians now recommend universal immunization for varicella for all susceptible children and adolescents. Although the varicella vaccine appears safe and efficacious, it is unknown how universal immunization will influence the epidemiology of varicella infections. The duration of immunity, both conferred and passive reinoculation, remains a concern and must continue to be evaluated in the population of vaccinees. As universal immunization is implemented, the cost-effectiveness of such a program will need to be evaluated. Physicians and parents must be educated about the risks and benefits of vaccination vs natural infection.