Epidemiology Of Varicella Research Articles

Immunity to Varicella Zoster Virus Among Young Adults: A Decline Prior to Widespread Uptake of Varicella Vaccines

The epidemiology of chickenpox in Israel is changing, mainly due to the increasing - but not universal - uptake of varicella vaccine. We conducted a seroprevalence study of varicella zoster virus (VZV) antibodies among 536 Israeli military recruits 18 years of age, on the basis of a representative sample of sera collected in 2003. The overall seroprevalence rate was 94.6%, which was significantly lower than that observed in a similar population in 1992 (98.4%, p < 0.001). The rate was lower among subjects whose fathers had less than 12 years of schooling (89.8%, p = 0.033). No statistically significant differences were observed when data were stratified by sex, subject's level of education, or origin. This decline in the level of immunity must be considered when determining pre- and post-exposure vaccination policy among young adults in crowded environments.

Changing Varicella Epidemiology in Active Surveillance Sites—United States, 1995–2005

Significant reductions in varicella incidence were reported from 1995 to 2000 in the varicella active surveillance sites of Antelope Valley (AV), California, and West Philadelphia (WP), Pennsylvania. We examined incidence rates, median age, and vaccination status of case patients for 1995-2005. Coverage data were from the National Immunization Survey. By 2005, coverage among children 19-35 months of age reached 92% (AV) and 94% (WP); 57% and 64% of case patients in AV and WP, respectively, were vaccinated; and varicella incidence declined by 89.8% in AV and 90.4% in WP. Incidence declined in all age groups, especially among children <10 years of age in both sites and among adolescents 10-14 years of age in WP. In AV, since 2000, the incidence among adolescents 10-14 and 15-19 years of age increased. Implementation of school requirements through 10th grade in WP may explain the differences in the decline in incidence among adolescents. Continued surveillance will be important to monitor the impact that the 2-dose vaccine policy in children has on varicella epidemiology.

Epidemiology of Varicella in Connecticut, 2001–2005

We analyzed varicella surveillance data in Connecticut for 2001-2005, to describe the epidemiology of varicella in a highly vaccinated population after the introduction of varicella vaccine and to determine the number of preventable cases that had occurred during school-related outbreaks. Overall, the incidence of varicella did not change during the surveillance period. Vaccination rates among reported case patients increased, and the severity of infection decreased. An annual median of 2.5 cases/outbreak was identified as being preventable, with a majority of these cases being preventable by revaccination of previously vaccinated persons. Continued surveillance is needed in order to monitor changing trends in varicella epidemiology.

The epidemiology of varicella in school-aged Greek children before the implementation of universal vaccination

Data on local epidemiology is necessary when deciding on the introduction of a vaccine. Parents of children attending 1st and 6th grades completed a questionnaire on demographical data and varicella history. Analyzing 70,226 questionnaires, varicella was reported in 63.6% and 78.6% of 1st and 6th grade children, respectively (mean age 4.75 years), indicating that a quarter of children entering adolescence are susceptible. Children attending day care and children with older siblings had contracted chickenpox at a younger age. In conclusion, in Greece, in addition to introducing universal varicella vaccination, it is necessary to identify older children at risk and offer catch-up vaccination.

Validity of Self-Reported Varicella Disease History in Pregnant Women Attending Prenatal Clinics

The purpose of this study was to assess the validity of self-reported history for varicella disease relative to serological evidence of varicella immunity in pregnant women attending antenatal care at clinics located in two diverse geographical locations in the U.S. (Antelope Valley, California, and Philadelphia) with high varicella vaccination coverage. Pregnant women attending prenatal care appointments who needed blood drawn as part of their routine care were eligible to participate. Self-reported varicella disease history was obtained via questionnaire. Varicella serostatus was determined using a whole-cell enzyme-linked immunosorbent assay to test for varicella zoster virus-specific immunoglobulin G (VZV IgG) antibodies. Of the 309 study participants from Antelope Valley and the 528 participants from Philadelphia who self-reported having had chickenpox disease, 308 (99.7%; 95% confidence interval [CI]: 98.2, 100) and 517 (97.9%; 95% CI: 96.3, 99.0), respectively, had serological evidence of immunity to varicella. Only 6.8% (95% CI: 3.9, 11.0) and 17.4% (95% CI: 13.1, 22.5) of women who self-reported having a negative or uncertain varicella disease history in Antelope Valley and Philadelphia, respectively, were seronegative for varicella antibodies. Despite the dramatic changes in the epidemiology of varicella that have occurred since 1995 due to the introduction and subsequent widespread use of the varicella vaccine, self-reported history of varicella continues to be a strong predictor of VZV IgG antibodies in pregnant women. Negative or uncertain history remains poorly predictive of negative serostatus.

Varicella vaccination in Europe: are we ready for a universal childhood programme?

Safe and effective vaccines against varicella zoster virus (VZV), the aetiological agent of varicella and shingles, have been available in Europe for the last 5-10 years. The USA has had a universal childhood vaccination policy since 1995 and this has resulted in a dramatic decrease in the incidence, morbidity and mortality related to varicella. The economic and medical burden of VZV has led to discussions regarding both the desirability and feasibility of a similar routine immunisation policy for all European children. This article examines the epidemiology of varicella in Europe and how the data emerging from the USA can be used to achieve adequate prevention of the disease. It looks into the current evidence of the health economic evaluation of universal varicella vaccination and explores the concerns surrounding such a policy, including the postulated impact on the incidence of zoster. In conclusion, the Society of Independent European Vaccination Experts (SIEVE) recommends that the immunisation of susceptible adolescents needs to be urgently implemented, in addition to the current recommendations targeting high-risk patients, their close contacts with a negative history of varicella and seronegative health-care workers. A universal policy, optimally incorporating a two-dose schedule, will be needed to finally reduce the burden of disease of varicella from a societal point of view. The SIEVE recommends the implementation of such a policy as soon as financially and practically possible.

Vaccination des adultes contre la varicelle et le zona

Following the commercialisation in France of the varicella vaccine and the European marketing authorization for a vaccine against zoster, this article intends to review the epidemiology of varicella and herpes zoster, to expose the characteristics of the available vaccines, and to consider the advantages and caveats of the different immunisation strategies. In France, from 550.000 to 750.000 cases of varicella are reported each year, which result in more than 3.500 hospitalizations and about 20 deaths. Subjects>or=15 years old represent 8.3% of the total number of cases of varicella, 26% of varicella-related hospitalisations and 69% of all varicella-related deaths. The susceptibility rate for the 15 years old is 10,3 and 79% of these non-immune subjects are expected to contract varicella. The vaccines currently marketed against varicella are safe, have a good immunogenicity and remain effective over the evaluated periods. Two vaccination strategies are considered: a generalized vaccination of the infants and children, or a vaccination targeted against high-risk populations and non-immune teenagers and adults. The incidence of herpes zoster is estimated in France at 235.000 new cases per year, from which 1% is hospitalized. A live attenuated vaccine using the same strain as the varicella vaccine, but at a much higher dose, proved its efficacy in terms of reducing shingles and postherpetic neuralgia incidences, of 51 and 67% respectively. This vaccine received a marketing authorisation in France, for adults>or=60 years old. Uncertainties about the impact of vaccination on varicella and herpes zoster epidemiology have yet to be solved, such as the potential increase in herpes zoster incidence or in the absolute number of diagnosed varicella cases in older age groups, or the loss of vaccination-induced immunity with time. These questions demonstrate the need for an operational real-time surveillance network to monitor varicella and herpes zoster incidence in the setting of general population immunisation.

Use of National Health Insurance database to evaluate the impact of public varicella vaccination program on burden of varicella in Taiwan

The aims of this study were to investigate the epidemiology of varicella and evaluate the effect of varicella vaccination on the burden of varicella in Taiwan. The outpatient and hospitalization claims made to the National Health Insurance (NHI) in public and private vaccination areas were compared during 2000–2002. In 2002, the outpatient visit rates for 1- to 5-year-old children in public vaccination areas were 66–78% lower than their counterparts in private vaccination areas. The reduction in outpatient visit rate was the greatest among preschool children. The reductions also occurred in every age group including infants and adults. This study showed significant evidence of vaccine impact with a marked decline in clinical cases in the short term.

The epidemiology of varicella and herpes zoster in The Netherlands: Implications for varicella zoster virus vaccination

We studied the epidemiology of varicella (chickenpox) and herpes zoster (shingles) in The Netherlands to assess the desirability to implement routine varicella zoster virus vaccination in The Netherlands. Data on seroprevalence of varicella zoster virus in the general population (1995–1996), consultations of general practitioners for varicella (2000–2002) and herpes zoster (1998–2001) and hospital admissions due to varicella (1994–2001) and herpes zoster (1994–2001) in The Netherlands were analysed. The seropositivity increased sharply with age from 18.4% for both 0- and 1-year-olds, to 48.9%, 59.0%, 75.7% and 93.0% for 2-, 3-, 4- and 5-year-olds, respectively, and varied between 97.5% and 100% for older age groups. The average annual incidence of GP-consultations amounted to 253.5 and 325.0 per 100,000 for varicella and herpes zoster, respectively. The incidence of hospital admission due to varicella and herpes zoster was 1.3 (2.3 including side diagnosis) and 2.7 (5.8) per 100,000, respectively. Whilst for varicella, the incidence of GP-consultations and hospital admissions were highest in childhood, for herpes zoster, these were highest in elderly. Insight into epidemiology of varicella zoster is needed for the assessment of the desirability of introduction of routine varicella zoster vaccination.

Update in varicella vaccination

Varicella, which is mostly a benign disease, but also can cause considerable health burden in the community, can be prevented by immunization with live attenuated varicella vaccine. Higher uptake of varicella vaccine by universal immunization in North America has apparently been associated with decline in the number of reported cases of varicella, varicella-related hospitalizations, and the number of deaths caused by complications of varicella. On the contrary, there has been some reluctance in endorsing varicella vaccine for universal immunization in most of European countries. Concerns include unanticipated outbreaks of varicella among vaccine recipients, risk of varicella among unvaccinated adults, risk of herpes zoster among vaccinees as well as unvaccinees. Recently developed measles, mumps, rubella, and varicella combination vaccine and herpes zoster vaccine that may be licensed in the upcoming years may be the solution for varicella vaccine to be utilized in a greater scale. In Korea several varicella vaccine products have been utilized since late 1980. The adoption of varicella vaccine for universal immunization since 2005 along with the changing view in varicella prevention strategy mandates more studies for immunogenecity and efficacy of varicella vaccines as well as more surveillance to delineate the changes in epidemiology of varicella in Korea.

The incidence of varicella and herpes zoster in Massachusetts as measured by the Behavioral Risk Factor Surveillance System (BRFSS) during a period of increasing varicella vaccine coverage, 1998-2003.

BackgroundThe authors sought to monitor the impact of widespread varicella vaccination on the epidemiology of varicella and herpes zoster. While varicella incidence would be expected to decrease, mathematical models predict an initial increase in herpes zoster incidence if re-exposure to varicella protects against reactivation of the varicella zoster virus.MethodsIn 1998–2003, as varicella vaccine uptake increased, incidence of varicella and herpes zoster in Massachusetts was monitored using the random-digit-dial Behavioral Risk Factor Surveillance System.ResultsBetween 1998 and 2003, varicella incidence declined from 16.5/1,000 to 3.5/1,000 (79%) overall with ≥66% decreases for all age groups except adults (27% decrease). Age-standardized estimates of overall herpes zoster occurrence increased from 2.77/1,000 to 5.25/1,000 (90%) in the period 1999–2003, and the trend in both crude and adjusted rates was highly significant (p < 0.001). Annual age-specific rates were somewhat unstable, but all increased, and the trend was significant for the 25–44 year and 65+ year age groups.ConclusionAs varicella vaccine coverage in children increased, the incidence of varicella decreased and the occurrence of herpes zoster increased. If the observed increase in herpes zoster incidence is real, widespread vaccination of children is only one of several possible explanations. Further studies are needed to understand secular trends in herpes zoster before and after use of varicella vaccine in the United States and other countries.

Varicella Vaccine and Infection with Varicella–Zoster Virus

Universal vaccination of susceptible children and adults has had a profound effect on the epidemiology of varicella. Drs. Marietta Vazquez and Eugene Shapiro discuss the question of whether vaccine-induced immunity in children will wane over time.

Epidemiology of severe varicella–zoster virus infection in Spain

Data of hospitalizations for varicella and herpes zoster in Spain during the 1999–2000 period were obtained from the national surveillance system for hospital data. A total of 3083 hospitalizations for varicella and 6324 for herpes zoster were identified, representing an annual incidence of 4.1 and 8.4 per 100,000 persons per year, respectively. Almost half of patients hospitalized for varicella were children under 5 years of age. In contrast, 78% of hospitalizations for zoster occurred in adults >50 years of age. Hospitalizations for varicella and herpes zoster resulted annually in 11,141 and 40,090 days of hospitalization and a cost of € 3.2 and 7.0 million, respectively.

The seroepidemiology and transmission dynamics of varicella in Australia.

To enhance our understanding of the epidemiology and transmission dynamics of varicella in the pre-vaccine era we performed a serosurvey using opportunistically collected sera submitted to diagnostic laboratories across Australia during 1997-1999. A representative sample by state and sex of 2027 sera from persons aged 1-49 years was tested using an enzyme immunoassay method. The average age of infection and age-specific forces of infection (the probability that a susceptible individual acquires infection) were calculated using published methodologies. Seropositivity increased with age, with 83% of sera positive by ages 10-14 years. The highest force of infection was in the 5-9 years age group (0.195 per susceptible year) followed by the 0-4 years age group (0.139 per susceptible year) and the average age of infection was 8.15 years. These results provide valuable baseline information to measure the impact of vaccination and indicate that vaccination should be aimed at children less than 5 years of age, although further modelling using the serosurvey data is warranted.

Epidemiology and economic impact of varicella in immunocompetent children in Spain.: A nation-wide study

The epidemiology and burden of varicella was assessed through the prospective study of 683 children under 15 years, by 58 primary care paediatricians working on seven autonomous communities of Spain. The mean age was 4.5±2.7 years, and 566 (83%) were secondary cases. There were 111 complications in 101 children (14.8%), skin superinfection being the most frequent (8.9%), followed by respiratory tract (4.5%) and eye (2.2%) infections. The mean number of visits to the paediatric clinic was 1.42 (95% C.I. 1.37–1.47), and 5.6% of the children were attended in the emergency department of a hospital previously. All children had at least one prescription, being antihistamines and antipyretics the most prescribed. Thirteen percent received systemic antibiotics and 11% acyclovir. Children were mainly cared by grandparents, and parents were off work for a mean of 0.97 days (1.61 if children under 5 years attended day-care facilities; 0.51 if they did not). Costs derived from medical attention totalled €32.5, and social indirect costs were €63.77.

Geographic and racial aspects of herpes zoster.

Geographic and racial factors have been reported in studies of the epidemiology of varicella and herpes zoster. To clarify further these relationships, data from five multicenter clinical trials of the antiviral agent famciclovir were examined (total N = 2074). Non-Caucasian racial group and tropical region were each significantly associated with younger age at zoster onset. In analyses of the non-Caucasian subgroups, Black and Asian patients did not significantly differ in age or sex; however, Black and Asian patients from tropical regions had significantly younger mean ages at onset and greater rash duration at enrollment than those from temperate regions. Controlling for sex and rash duration at enrollment, both tropical region and non-Caucasian racial group were found to be independently associated with a younger age at zoster onset. These results suggest that racial group and geographic region may be independent factors associated with age at onset in patients with herpes zoster.

Varicella susceptibility and vaccine use among young adults enlisting in the United States Navy.

Primary varicella infection, or chicken pox, is a threat to all young adults who join the United States (U.S.) military if they fail to develop immunity prior to enlistment. Historically, outbreaks of chicken pox have caused marked morbidity and impaired military readiness. In December 1996, the U.S. Navy began performing serologic testing for varicella among all new recruits, and vaccinating those found to be sero-negative. We evaluated results of the screening program in its first 4 years, and used multivariable logistic regression modeling to describe factors associated with varicella susceptibility. Cases of chicken pox were tracked among all military services before and after program implementation. More than 190,000 young adults enlisted in the U.S. Navy between 1997 and 2000. Recruits originated from all 50 states and several foreign countries; 84% were male, and their average age was 19 years. Seven percent were found to be susceptible (sero-negative) to varicella. In multivariable modeling, race/ethnicity was associated with susceptibility, but age, gender, and home state were not. The overall incidence of chicken pox in the Navy was reduced by more than 80% after initiation of the screening-vaccination program. A successful varicella screening-vaccination program has been implemented in the U.S. Navy. Results of serologic screening undertaken on this large number of young adults may be useful in tracking the changing epidemiology of varicella in the general population in the post-vaccine era.

Hospitalizations for varicella in the United States, 1988 to 1999

Varicella epidemiology is changing with increasing use of the varicella vaccine. To describe the epidemiology of severe varicella disease before and after vaccine introduction, data from the National Hospital Discharge Survey (NHDS) for 1988 to 1999 were analyzed. Incidental cases of varicella in persons hospitalized for a different indication were excluded. In the prevaccination era (1988 to 1995), there were 10 632 varicella hospitalizations annually. The most common complications were viral pneumonitis (20.9%), fluid/electrolyte disturbances (19.3%) and soft tissue infections (17.8%). Most (89.1%) persons had no severe underlying immunocompromising conditions. The mean length of hospitalization was 5.4 days, corresponding to approximately 57 000 days of hospitalization annually. In the first years after vaccine licensure (1996 to 1999), vaccine coverage reached 59%. Although not statistically significant, there was a trend toward decreased hospitalizations and a decline in mean length of hospitalization. Varicella morbidity was higher in the prevaccination era than previously reported. Although no significant decline is evident, a trend toward decreased hospitalizations is emerging in the first years after vaccine introduction.

Varicella transmission in two samples of children with different social behaviour in the State of São Paulo, Brazil.

In order to establish the differences in transmission pattern of varicella-zoster virus (VZV), a comparative seroepidemiological study was carried out in two different children samples. Children aged 1-11 years, were randomly selected from state schools of São Paulo city, Brazil. Individuals aged 1-15 years were sampled by cluster from Caieiras city. Children aged 3 years or under from Caieiras were not attending school, while those from São Paulo were attending all-day nurseries or kindergarten. The presence of antibodies to VZV was analysed by ELISA technique. The force of infection and contact rate were determined by mathematical techniques. The average age of first infection was 2.87 +/- 0.14 years and 4.07 +/- 0.47 years for Sao Paulo and Caieiras, respectively. The average force of infection estimated was 0.29 year(-1) for São Paulo and was 0.26 year(-1) for Caieiras. The proportion of seropositivity and the force of infection were higher in São Paulo school children up to 3 years of age compared with Caieiras children, where the social contact starts later. In conclusion, social changes affecting contact among children may influence varicella epidemiology.

Epidemiology of varicella zoster virus infection in Canada and the United Kingdom.

Many countries are currently studying the possibility of mass vaccination against varicella. The objective of this study was to provide a comprehensive picture of the pre-vaccine epidemiology of the varicella zoster virus (VZV) to aid in the design of immunization programs and to adequately measure the impact of vaccination. Population-based data including physician visit claims, sentinel surveillance and hospitalization data from Canada and the United Kingdom were analysed. The key epidemiological characteristics of varicella and zoster (age specific consultation rates, seasonality, force of infection, hospitalization rates and inpatient days) were compared. Results show that the overall epidemiology of varicella and zoster is remarkably similar between the two countries. The major difference being that, contrary to Canada, the epidemiology of varicella seems to be changing in the United Kingdom with an important decrease in the average age at infection that coincides with a significant increase in children attending preschool. Furthermore, differences exist in the seasonality between the United Kingdom and Canada, which seem to be primarily due to the school calendar. These results illustrate that school and preschool contact patterns play an important role in the dynamics of varicella. Finally, our results provide baseline estimates of varicella and zoster incidence and morbidity for VZV vaccine effectiveness and cost-effectiveness studies.