Varicella disease after introduction of varicella vaccine in the United States, 1995-2000

Modeling the impact of one- and two-dose varicella vaccination on the epidemiology of varicella and zoster

In many countries, policymakers are being asked to make recommendations regarding the introduction of a 2-dose varicella vaccination program. The objective of this study was to examine the potential impact of 1-dose versus 2-dose varicella vaccination programs on varicella and zoster incidence, using Canada as an example. We developed a deterministic realistic age-structured model that fits 1- and 2-dose vaccine efficacy, varicella force of infection and zoster incidence. Assuming 90% coverage, the base case model (range: min; max) predicts that 1-dose vaccination will reduce varicella and zoster cases by 64% (14%; 96%) and 5% (-2%; 22%), respectively, over 80-years. Adding a second dose is predicted to reduce varicella and zoster by an additional 22% (0%; 82%) and 6% (0%; 14%), respectively. Most varicella cases prevented by the second dose are breakthrough infections. Although the incremental effectiveness of adding the second dose is highly sensitive to vaccine efficacy and mixing, predictions of the overall benefit of a 2-dose program is relatively robust to model assumptions. Adding a 2-dose program may help guarantee high population-level effectiveness against varicella. However, the incremental benefit of a second dose is highly dependant on the effectiveness of the first dose and its impact on zoster.

Decline in varicella-related ambulatory visits and hospitalizations in the United States since routine immunization against varicella

BACKGROUND

Widespread varicella vaccination has led to substantial decreases in varicella-related mortality and hospitalizations. The effect of the vaccine on ambulatory care utilization is poorly defined.

OBJECTIVE

To determine trends in varicella-related ambulatory care and hospital discharges before and after vaccine licensure.

DESIGN, SETTING, AND PARTICIPANTS

Estimates of varicella-related ambulatory and hospital discharges were calculated for the pre- (1993-1995) and post- (1996-2004) vaccine licensure periods using the National Ambulatory Medical Care Survey, National Hospital Ambulatory Medical Care Survey, and National Hospital Discharge Survey.

MAIN OUTCOME MEASURE

Ambulatory and hospital discharge rates for varicella.

RESULTS

The rate of varicella-related ambulatory discharges decreased by 66% from 106.6 per 100,000 (95% confidence interval [CI]: 80.5-132.6) in the prelicensure period to 36.4 per 100,000 population (95% CI: 29.3-43.5) in the post-licensure period (P < 0.001). The decrease was significant across all age groups <45 years, with the greatest reduction (98%) occurring among patients 0 to 4 years of age. The incidence of varicella-related hospital discharges decreased by 53% from 30.9 per 100,000 (95% CI: 24.4-37.3) to 14.5 per 100,000 population (95% CI: 12.1-16.8; P < 0.001). This difference was significant among patients <14 years of age. Rates of varicella-related ambulatory discharges decreased significantly for both whites and non-whites in the postlicensure period, but postlicensure ambulatory discharge rates remained higher for non-whites than for whites. Decreases in varicella-related hospital discharges were statistically significant for whites and non-whites. Racial differences in the incidence of varicella-related hospital discharges also persisted following vaccine licensure.

CONCLUSIONS

Varicella-related ambulatory visits and hospitalizations have decreased significantly in the period after licensure of the varicella vaccine.

A decline in varicella but an uncertain impact on zoster following varicella vaccination in Victoria, Australia

Varicella vaccine was licensed in Australia in 1999 and publicly funded in 2005. We examined trends in varicella and zoster hospitalisations and community consultations in Victoria during periods of no vaccine, private availability of vaccine and funded vaccination. Varicella hospitalisation rates declined 7% per year (95% CI 5-9%) from 2000 to 2007, predominately in children under five (12% per year, 95% CI 9-16%). A similar decline was seen in community data. The zoster hospitalisation rate increased from 1998 to 2007 (5% per year, 95% CI 3-6%), before introduction of varicella vaccine. Among those aged 80 and over the hospitalisation rate increased 5% per year (95% CI 3-7%) from 1998 to 2007. Zoster increased in community data from 2001.

Herpes zoster and exposure to the varicella zoster virus in an era of varicella vaccination

OBJECTIVES

We performed a case-control study to determine if participants with herpes zoster had fewer contacts with persons with varicella or zoster, and with young children, to explore the hypothesis that exposure to persons with varicella zoster virus (VZV) results in "immune boosting."

METHODS

Participants were patients of the multispecialty Marshfield Clinic in Wisconsin. We identified patients aged 40 to 79 years with a new diagnosis of zoster from August 2000 to July 2005. We frequency matched control participants to case participants for age. We confirmed diagnoses by chart review and assessed exposures by interview.

RESULTS

Interviews were completed by 633 of 902 eligible case participants (70.2%) and 655 of 1149 control participants (57.0%). The number of varicella contacts was not associated with zoster; there was no trend even at the highest exposure level (3 or more contacts). Similarly, there was no association with exposure to persons with zoster or to children, or with workplace exposures.

CONCLUSIONS

Although exposure to VZV in our study was relatively low, the absence of a relationship with zoster reflects the uncertain influence of varicella circulation on zoster epidemiology.

Varicella-zoster virus vaccine: molecular genetics

The genetic differences that potentially account for the attenuation of the Oka vaccine VZV preparation are more clearly defined than for perhaps any other vaccine in current use. This is due in large part to the small number of differences between the vaccine and the parental strain from which it was derived, and to the high level of genomic conservation that characterizes VZV. This information has been used with great success to develop methods that discriminate vaccine from wild-type strains, to begin determining which specific vaccine markers contribute to the attenuated phenotype, to improve evaluations of vaccine efficacy and safety, and to observe the behavior of the live, attenuated preparation as it becomes more prevalent through widespread immunization.

Neurologic varicella complications before routine immunization in Germany

Varicella is an acute febrile, highly infectious disease. We describe the incidence and types of neurologic complications in children up to 16 years old. Hospitalized varicella cases were prospectively captured by active nationwide surveillance through the German Pediatric Surveillance Unit for Rare Diseases from January 2003 to December 2004. Neurologic complications occurred in 232 (25.4%) of 918 hospitalized children with varicella, and were the most frequent reason for hospitalization. The median age was 4.2 years (interquartile range 2.5-5.9). The median duration of hospital stay was 6 days (interquartile range 3-11). Neurologic complications were more frequent (P=0.054) in immunocompetent (32%) than immunocompromised (4%) children. The most frequent diagnoses comprised acute cerebellar ataxia in 72 (31.0%), febrile convulsion in 69 (29.7%), meningoencephalitis in 52 (22.4%), cerebral convulsions in 21 (9.1%), syncope in 9 (3.9%), and cerebral vasculitis/infarction in 6 (2.6%) of all children with neurologic complications. Twenty-eight (12%) demonstrated sequelae (18 with ataxia, four with epilepsy, two with hemiparesis, three with cerebral nerve palsy, and one with dysesthesia). Three patients died. The yearly incidence of neurologic varicella-associated hospitalizations was estimated at 2.4 neurologic complications per 100,000 children, corresponding to about one neurologic complication in 2000 varicella cases.

Intravenous immunoglobulin in children with streptococcal toxic shock syndrome

BACKGROUND

Streptococcal toxic shock syndrome (TSS) is a rare and severe manifestation of group A streptococcal infection. The role of intravenous immunoglobulin (IVIG) for streptococcal TSS in children is controversial. This study aims to describe the epidemiology of streptococcal TSS in children and to determine whether adjunctive therapy with IVIG is associated with improved outcomes.

METHODS

A multicenter, retrospective cohort study of children with streptococcal TSS from 1 January 2003 through 31 December 2007 was conducted. Propensity scores were used to determine each child's likelihood of receiving IVIG. Differences in the primary outcomes of death, hospital length of stay, and total hospital costs were compared after matching IVIG recipients and nonrecipients on propensity score.

RESULTS

The median patient age was 8.2 years. IVIG was administered to 84 (44%) of 192 patients. The overall mortality rate was 4.2% (95% confidence interval, 1.8%-8.0%). Differences in mortality between IVIG recipients (n = 3; 4.5%) and nonrecipients (n = 3; 4.5%) were not statistically significant (p > .99). Although patients receiving IVIG had higher total hospital and drug costs than nonrecipients, differences in hospital costs were not significant once drug costs were removed (median difference between matched patients, $6139; interquartile range, -$8316 to $25,993; P = .06). No differences were found in length of hospital stay between matched IVIG recipients and nonrecipients.

CONCLUSION

This multicenter study is, to our knowledge, the largest to describe the epidemiology and outcomes of children with streptococcal TSS and the first to explore the association between IVIG use and clinical outcomes. IVIG use was associated with increased costs of caring for children with streptococcal TSS but was not associated with improved outcomes.

[A live attenuated varicella vaccine]

The vaccine virus was isolated from a vesicle of a 3-year-old otherwise healthy boy called Oka (his family name) who had typical varicella. This virus was passaged through human embryonic lung cells, guinea pig embryonic cells at a low temperature, and human diploid cells (WI-38). It was then adapted to MRC-5 human diploid cells for vaccine preparation. The vaccine contains cell-free virus with a minimum of 1000 plaque forming units per dose and suitable stabilizers. In 1974 the vaccine was administered to hospitalized children immediately after the occurrence of an index varicella case because preventive methods, such as administration of VZV immune globulin, were unavailable at the time. The vaccine prevented the spread of varicella throughout the children's ward of the hospital. Subsequently, the vaccine was shown to be immunogenic, well tolerated, and efficacious even in high-risk children. The vaccine has been studied extensively with largely favorable results. The vaccine was initially licensed in Japan in 1987 for high-risk children but was extended just after licensure to include normal children based on the needs of parents and physicians. Because varicella vaccination is not compulsory in Japan, only approximately 40% of Japanese children received the vaccine in 2008. This low level of coverage was not sufficient to alter the circulation of wild-type VZV, and the epidemiology of natural varicella has not changed since the vaccine was introduced. The most dramatic changes were reported in the USA after the introduction of a universal immunization strategy in 1996, causing vaccine coverage to increase to 89% in 2006. As a result, there have been substantial declines among both children and adults in the incidence of varicella, hospitalizations and ambulatory visits for varicella, mortality due to varicella, varicella-related complications, and overall expenditures for varicella-related illnesses. The vaccine is now commercially available worldwide and was administered to approximately 16 million individuals in approximately 80 countries in 2006. The universal immunization strategy should be introduced in Japan as soon as possible.

Caracterização epidemiológica dos casos de varicela em pacientes internados em um hospital universitário da cidade do Recife

A varicela é uma doença cosmopolita, com contagiosidade extremamente acentuada, causada pelo vírus Varicela - Zoster. Embora considerada uma doença benigna da infância, atualmente tem-se demonstrado uma crescente incidência de complicações severas com um alto potencial de morbi-mortalidade em crianças e adultos previamente saudáveis. O trabalho tem como objetivo caracterizar o perfil epidemiológico dos casos de varicela em pacientes internados em um hospital universitário da cidade do Recife. Trata-se de um estudo do tipo descritivo-exploratório com abordagem quantitativa, realizado no período de janeiro de 2004 a janeiro de 2005 em pacientes internados por varicela no Hospital Universitário Oswaldo Cruz da cidade do Recife. Observou-se que, do total de 255 pacientes internados por varicela, 53% eram do sexo masculino; 77,3% dos casos apresentaram como complicação predominante as infecções bacterianas secundárias da pele, sendo a celulite a mais freqüente, em 48,1% dos casos; verificou-se que 2% evoluíram a óbito; constatou-se na análise dos custos e benefícios que ocorreria uma economia de R$ 61.710,00 se a população em estudo fosse vacinada. A pesquisa apresenta dados que fundamentam a importância da redução no número de casos da doença, tendo em vista que existe a possibilidade de uma evolução não satisfatória e, inclusive, evolução ao óbito. Nesse sentido, esses achados poderão nortear os gestores de saúde na adoção de condutas preventivas e no planejamento das ações de saúde.

The incidence and clinical characteristics of herpes zoster among children and adolescents after implementation of varicella vaccination

BACKGROUND

The varicella-zoster virus (VZV) vaccine strain may reactivate to cause herpes zoster. Limited data suggest that the risk of herpes zoster in vaccinated children could be lower than in children with naturally acquired varicella. We examine incidence trends, risk and epidemiologic and clinical features of herpes zoster disease among children and adolescents by vaccination status.

METHODS

Population-based active surveillance was conducted among <20 years old residents in Antelope Valley, California, from 2000 through 2006. Structured telephone interviews collected demographic, varicella vaccination and disease histories, and clinical information.

RESULTS

From 2000 to 2006, the incidence of herpes zoster among children<10 years of age declined by 55%, from 42 cases reported in 2000 (74.8/100,000 persons; 95% confidence interval [95% CI]: 55.3-101.2) to 18 reported in 2006 (33.3/100,000; 95% CI: 20.9-52.8; P<0.001). During the same period, the incidence of herpes zoster among 10- to 19-year-olds increased by 63%, from 35 cases reported in 2000 (59.5/100,000 persons; 95% CI: 42.7-82.9) to 64 reported in 2006 (96.7/100,000; 95% CI: 75.7-123.6; P<0.02). Among children aged<10 years, those with a history of varicella vaccination had a 4 to 12 times lower risk for developing herpes zoster compared with children with history of varicella disease.

CONCLUSIONS

Varicella vaccine substantially decreases the risk of herpes zoster among vaccinated children and its widespread use will likely reduce overall herpes zoster burden in the United States. The increase in herpes zoster incidence among 10- to 19-year-olds could not be confidently explained and needs to be confirmed from other data sources.

Varicella zoster virus vaccines: effective, but concerns linger

Both varicella and herpes zoster (HZ) can cause severe disease in certain age groups. The cell-mediated immune (CMI) response to the varicella zoster virus (VZV) is critical in preventing a recurrence of VZV. The varicella vaccine has markedly decreased the morbidity and mortality associated with varicella, but concerns linger about the cost and frequency of vaccine administration and the long-term effects on both adult varicella and HZ epidemiology in the individual and in the population. Therapy for HZ with an antiviral is only partially effective. A zoster vaccine is now available that boosts the CMI immune reaction to VZV in individuals and has proven safe and partially effective in preventing both HZ and post-herpetic neuralgia. Concerns about the zoster vaccine include the costs of administration, the overall health-care costs to society, and the acceptance and implementation of the vaccine in the elderly. Because of altered immune responses to VZV as a result of universal varicella vaccination it becomes even more compelling in the future to have a zoster vaccine ready to boost the CMI response to a sufficient level to prevent HZ. The 2 vaccines are intertwined in the future epidemiology of VZV disease.

Varicella: epidemiological aspects and vaccination coverage in the Veneto Region

Background

With the control of many infections through national vaccination programmes, varicella is currently the most widespread preventable childhood disease in industrialized nations. In 2005 varicella vaccination was added to the Veneto Region routine immunization schedule for all children at 14 months of age and 12 year-old susceptible adolescents through an active and a free of charge offer. To evaluate parameters at the start of the programme, we conducted a study to describe the epidemiology of varicella infection and coverage rates for varicella vaccine in the Veneto Region (North-East Italy).

Methods

We examined incidence rates and median age of case patients in the Veneto Region for 2000-2007 period using two data sources: the mandatory notification of infections diseases and the Italian Paediatric Sentinel Surveillance System of Vaccine Preventable Diseases. Corrected coverage rates were calculated from data supplied by the Public Health and Screening Section of the Regional Department for Prevention.

Results

In the Veneto Region from 2000 to 2007, a total of 99,351 varicella cases were reported through mandatory notifications, mostly in children under 15 years of age. The overall standardised annual incidence ranged from 2.0 to 3.3 per 1,000 population, with fluctuations from year to year. The analysis by geographic area showed a similar monthly incidence rate in Italy and in the Veneto Region. The vaccination average adherence rate was 8.2% in 2004 cohort, 63.5% in 2005 cohort and 86.5% in 2006 cohort. Corrected coverage rates were 8.1% in 2004 cohort, 59.9% in 2005 cohort and 70.0% in 2006 cohort, respectively.

Conclusion

Data from passive and active surveillance systems confirm that varicella is a common disease which each year affects a large proportion of the population, mainly children. Uptake of the varicella vaccination programme was strikingly good with average coverage rates of about 70% after only 3 years. Sustained implementation of existing vaccine policies is needed to warrant any significant reduction of varicella incidence in the Veneto Region. Continued surveillance will be important to monitor the impact of the recently introduced mass vaccination policy.

Varicella-specific immunoglobulin G titers in commercial intravenous immunoglobulin preparations

BACKGROUND AND OBJECTIVES

Since the introduction of an effective vaccine in 1995, the incidence of primary varicella zoster virus (VZV) has greatly decreased. However, newborns and immunocompromised patients remain at risk for serious disease. Currently, varicella-specific immunoglobulin is recommended for treatment of nonimmune, exposed, high-risk patients with varicella-specific immunoglobulin. However, product inavailability has led to substitution of intravenous immunoglobulin (IVIg) for such prophylaxis on the basis of studies from the preimmunization era. No studies in the post-vaccine era have shown that IVIg contains adequate varicella-specific antibodies to protect patients at high risk. The overall effect of vaccination on varicella-specific immunoglobulin G (IgG) levels in donor-pooled IVIg products is unknown. We compared the varicella-specific IgG levels in prevaccine and current IVIg products.

METHODS

We used stored historic IVIg samples and current samples from our inpatient pharmacy. All samples were tested for varicella-specific IgG levels by enzyme-linked immunosorbent assay.

RESULTS

Ten historic lots and 24 current lots were tested. The overall mean value of varicella-specific IgG in the historic lots was 3.07 (SD: 0.70); the current lots had a mean of 3.83 (SD: 0.58). The postvaccine IVIg contained higher levels of antibody than the prevaccine lots.

CONCLUSIONS

We found that current IVIg preparations continue to have high levels of varicella-specific IgG despite the changing epidemiology of how immunity has been obtained. Given the results of this study, it is reasonable for physicians to comfortably substitute IVIg for varicella-specific immunoglobulin preparations when treating high-risk patients exposed to VZV.

A combined measles, mumps, rubella and varicella vaccine (Priorix-Tetra): immunogenicity and safety profile

Priorix-Tetra (GlaxoSmithKline Biologicals) is a combined measles, mumps, rubella and varicella (MMRV) vaccine. Eight studies involving more than 3000 children were reviewed. Compared with co-administration of MMR (Priorix) and varicella (Varilrix) vaccines, the MMRV vaccine showed: similar immunogenicity, with immunity shown up to 3 years post-vaccination; a higher rate of fever after the first dose; a slight increase in mild local reactions after the second dose. This MMRV vaccine can be used either as a two-dose vaccine or as a second dose in children primed with separate MMR and/or varicella vaccines, offering a convenient way to introduce varicella vaccination into routine vaccination programmes.

Varicella vaccination in Europe - taking the practical approach

Varicella is a common viral disease affecting almost the entire birth cohort. Although usually self-limiting, some cases of varicella can be serious, with 2 to 6% of cases attending a general practice resulting in complications. The hospitalisation rate for varicella in Europe ranges from 1.3 to 4.5 per 100,000 population/year and up to 10.1% of hospitalised patients report permanent or possible permanent sequelae (for example, scarring or ataxia). However, in many countries the epidemiology of varicella remains largely unknown or incomplete. In countries where routine childhood vaccination against varicella has been implemented, it has had a positive effect on disease prevention and control. Furthermore, mathematical models indicate that this intervention strategy may provide economic benefits for the individual and society. Despite this evidence and recommendations for varicella vaccination by official bodies such as the World Health Organization, and scientific experts in the field, the majority of European countries (with the exception of Germany and Greece) have delayed decisions on implementation of routine childhood varicella vaccination, choosing instead to vaccinate high-risk groups or not to vaccinate at all. In this paper, members of the Working Against Varicella in Europe group consider the practicalities of introducing routine childhood varicella vaccination in Europe, discussing the benefits and challenges of different vaccination options (vaccination vs. no vaccination, routine vaccination of infants vs. vaccination of susceptible adolescents or adults, two doses vs. one dose of varicella vaccine, monovalent varicella vaccines vs. tetravalent measles, mumps, rubella and varicella vaccines, as well as the optimal interval between two doses of measles, mumps, rubella and varicella vaccines). Assessment of the epidemiology of varicella in Europe and evidence for the effectiveness of varicella vaccination provides support for routine childhood programmes in Europe. Although European countries are faced with challenges or uncertainties that may have delayed implementation of a childhood vaccination programme, many of these concerns remain hypothetical and with new opportunities offered by combined measles, mumps, rubella and varicella vaccines, reassessment may be timely.

Vaccine refusal, mandatory immunization, and the risks of vaccine-preventable diseases

Vaccines are among the most effective prevention tools available to clinicians. However, the success of an immunization program depends on high rates of acceptance and coverage. There is evidence of an increase in vaccine refusal in the United States and of geographic clustering of refusals that results in outbreaks. Children with exemptions from school immunization requirements (a measure of vaccine refusal) are at increased risk for measles and pertussis and can infect others who are too young to be vaccinated, cannot be vaccinated for medical reasons, or were vaccinated but did not have a sufficient immunologic response. Clinicians can play a crucial role in parental decision making. Health care providers are cited as the most frequent source of immunization information by parents, including parents of unvaccinated children. Although some clinicians have discontinued or have considered discontinuing their provider relationship with patients who refuse vaccines, the American Academy of Pediatrics Committee on Bioethics advises against this and recommends that clinicians address vaccine refusal by respectfully listening to parental concerns and discussing the risks of nonvaccination.

Validity of reported varicella history as a marker for varicella zoster virus immunity among unvaccinated children, adolescents, and young adults in the post-vaccine licensure era

OBJECTIVES

We assessed the validity of reported varicella history as a marker for varicella zoster virus immunity among unvaccinated persons 1 to 29 years of age, and we examined varicella disease characteristics associated with varicella zoster virus immunity among those reporting positive histories.

METHODS

We conducted a cross-sectional study at 7 community-based sites in Philadelphia, Pennsylvania, between June 2004 and May 2006 and recruited 1476 participants 1 to 29 years of age who had not been vaccinated against varicella. Sensitivity, specificity, and positive predictive value were determined by comparing self-reported or parent-reported varicella histories from a standardized study interview with varicella zoster virus immunoglobulin G serological results for each participant. We performed multivariate logistic regression analyses to determine which disease characteristics best predicted seropositivity.

RESULTS

The sensitivity of reported varicella history was highest (81%-89%) among participants > or =10 years of age, whereas specificity was highest among participants 1 to 4 years of age (99%) and > or =20 years (88%). Reported varicella history was highly predictive of seropositivity (>95%) only among participants > or =15 years of age. For participants 10 to 14 years of age, parental reports of a generalized itchy rash with 1 of the following were highly predictive of seropositivity: varicella transmission to another household member or being raised in a household with no other children. Among participants < or =9 years of age, no combination of disease characteristics was both highly predictive of seropositivity and common.

CONCLUSIONS

The validity of reported varicella history varies according to age, and a reported history is no longer highly predictive of seropositivity among cohorts born since 1994 (participants < or =9 years of age). Universal varicella vaccination, regardless of history, for these children should be considered, as should simplified criteria for varicella zoster virus immunity among unvaccinated persons born before 1994.

Immunogenicity and safety of concomitant administration of a measles, mumps and rubella vaccine (M-M-RvaxPro) and a varicella vaccine (VARIVAX) by intramuscular or subcutaneous routes at separate injection sites: a randomised clinical trial

BACKGROUND

When this trial was initiated, the combined measles, mumps and rubella (MMR) vaccine was licensed for subcutaneous administration in all European countries and for intramuscular administration in some countries, whereas varicella vaccine was licensed only for subcutaneous administration. This study evaluated the intramuscular administration of an MMR vaccine (M-M-RvaxPro) and a varicella vaccine (VARIVAX) compared with the subcutaneous route.

METHODS

An open-label randomised trial was performed in France and Germany. Healthy children, aged 12 to 18 months, received single injections of M-M-RvaxPro and VARIVAX concomitantly at separate injection sites. Both vaccines were administered either intramuscularly (IM group, n = 374) or subcutaneously (SC group, n = 378). Immunogenicity was assessed before vaccination and 42 days after vaccination. Injection-site erythema, swelling and pain were recorded from days 0 to 4 after vaccination. Body temperature was monitored daily between 0 and 42 days after vaccination. Other adverse events were recorded up to 42 days after vaccination and serious adverse events until the second study visit.

RESULTS

Antibody response rates at day 42 in the per-protocol set of children initially seronegative to measles, mumps, rubella or varicella were similar between the IM and SC groups for all four antigens. Response rates were 94 to 96% for measles, 98% for both mumps and rubella and 86 to 88% for varicella. For children initially seronegative to varicella, 99% achieved the seroconversion threshold (antibody concentrations of >or= 1.25 gpELISA units/ml). Erythema and swelling were the most frequently reported injection-site reactions for both vaccines. Most injection-site reactions were of mild intensity or small size (<or= 2.5 cm). There was a trend for lower rates of injection-site erythema and swelling in the IM group. The incidence and nature of systemic adverse events were comparable for the two routes of administration, except varicella-like rashes, which were less frequent in the IM group.

CONCLUSION

The immunogenicities of M-M-RvaxPro and VARIVAX administered by the intramuscular route were comparable with those following subcutaneous administration, and the tolerability of the two vaccines was comparable regardless of administration route. Integration of both administration routes in the current European indications for the two vaccines will now allow physicians in Europe to choose their preferred administration route in routine clinical practice.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00432523.

Predictors of cerebral arteriopathy in children with arterial ischemic stroke: results of the International Pediatric Stroke Study

BACKGROUND

Cerebral arteriopathies, including an idiopathic focal cerebral arteriopathy of childhood (FCA), are common in children with arterial ischemic stroke and strongly predictive of recurrence. To better understand these lesions, we measured predictors of arteriopathy within a large international series of children with arterial ischemic stroke.

METHODS AND RESULTS

Between January 2003 and July 2007, 30 centers within the International Pediatric Stroke Study enrolled 667 children (age, 29 days to 19 years) with arterial ischemic stroke and abstracted clinical and radiographic data. Cerebral arteriopathy and its subtypes were defined using published definitions; FCA was defined as cerebral arterial stenosis not attributed to specific diagnoses such as moyamoya, arterial dissection, vasculitis, or postvaricella angiopathy. We used multivariate logistic regression techniques to determine predictors of arteriopathy and FCA among those subjects who received vascular imaging. Of 667 subjects, 525 had known vascular imaging results, and 53% of those (n=277) had an arteriopathy. The most common arteriopathies were FCA (n=69, 25%), moyamoya (n=61, 22%), and arterial dissection (n=56, 20%). Predictors of arteriopathy include early school age (5 to 9 years), recent upper respiratory infections, and sickle cell disease, whereas prior cardiac disease and sepsis reduced the risk of arteriopathy. The only predictor of FCA was recent upper respiratory infection.

CONCLUSIONS

Arteriopathy is prevalent among children with arterial ischemic stroke, particularly those presenting in early school age, and those with a history of sickle cell disease. Recent upper respiratory infection predicted cerebral arteriopathy and FCA in particular, suggesting a possible role for infection in the pathogenesis of these lesions.

Short-term and long-term effects of highly active antiretroviral therapy on the incidence of herpes zoster in HIV-infected children

BACKGROUND

Highly active antiretroviral therapy (HAART) has reduced herpes zoster (HZ) incidence in HIV-infected children, yet it remains common.

METHODS

We evaluated perinatally HIV-infected youth with varicella infection enrolled between 1993 and 2006 in a prospective cohort study. Incidence rates (IRs) and 95% confidence intervals of HZ were estimated by calendar year, age group, and HAART use. The effect of initiating HAART was also evaluated by fitting Cox survival models adjusted for potential confounders.

RESULTS

Among 536 perinatally infected children with documented prior varicella (median follow-up = 6.8 years), 116 (22%) developed HZ (IR = 3.2 events/100 person-years, confidence interval: 2.6 to 3.8). IRs increased from 1993 to 1996 and then declined significantly through 2006 (P < 0.001). However, an IR of 1.4-3.1 HZ episodes per 100 person-years persisted from 2001 to 2006. The risk of HZ was higher for those with lower CD4% or in Centers for Disease Control and Prevention clinical class C. The IR of HZ was similar in the 90 days before or after initiation of HAART but declined significantly after more than 90 days of HAART.

CONCLUSIONS

Although HAART has markedly reduced the IR of HZ, it remains a frequent complication in HIV-infected children. The risk of HZ is similar in the 90 days before and after initiating HAART.

Herpes zoster-related hospitalizations and expenditures before and after introduction of the varicella vaccine in the United States

OBJECTIVE

With childhood varicella vaccination in the United States have come concerns that the incidence of herpes zoster may increase, because of diminishing natural exposure to varicella and consequent reactivation of latent varicella zoster virus. We wanted to estimate the rate of herpes zoster-related hospitalizations and the associated hospital charges before and during the promotion of varicella vaccination in the United States.

DESIGN

A retrospective study of patients from the Nationwide Inpatient Sample for the years 1993-2004 who were hospitalized due to herpes zoster infection.

METHODS

We searched for diagnoses of herpes zoster (using the International Classification of Diseases, Ninth Revision, Clinical Modification codes starting with 053) in all 15 diagnostic-code fields included for hospital discharges in the Nationwide Inpatient Sample during 1993-2004. We designed our analysis to examine the rates of severe illness due to herpes zoster that resulted in hospitalization, as measured by the rates of herpes zoster-related hospital discharges (HZHDs). The annual population-adjusted rate of HZHDs (per 10,000 US population) and the annual inflation-adjusted total charges for HZHDs were the primary outcomes. Secondary outcomes included mean charges for HZHDs and the distribution of total charges for HZHDs by expected primary payer. Varicella-related hospital discharges (VRHDs) were identified by use of similar diagnosis-based methods, which were described in our previous study.

RESULTS

Population-adjusted rates of HZHDs did not change significantly from the prevaccination years (1993-1995) through the initial 5 years of the varicella vaccination period. Beginning in 2001, however, the rate of HZHDs overall began to increase, and by 2004 the overall rate was 2.5 HZHDs (95% confidence interval, 2.38-2.62) per 10,000 US population, significantly higher than any of the rates calculated during the years prior to 2002. Hospital charges for HZHDs overall increased by more than $700 million annually by 2004; in particular, we found that the herpes zoster vaccine-eligible population (ie, persons aged 60 years or older) accounted for 74% of the total annual hospital charges in 2004. The annual rate of VRHDs and the associated hospital charges decreased significantly from 1993 through 2004, but the decrease in hospitalizations and charges for VRHDs was less than the increase in hospitalizations and charges for HZHDs.

CONCLUSIONS

As the rates of VRHDs and the associated charges have decreased, there has been a significant increase in HZHDs and associated charges, disproportionately among older adults. Herpes zoster vaccine may mitigate these trends for HZHDs.

Incidence of chickenpox in young South Korean soldiers and correlation with atopic dermatitis

BACKGROUND

In South Korea, military service is compulsory for all healthy young men and provides specific environmental factors, with groups working and living together in specific places for several years making varicella more transmissible to susceptible individuals. Studies of people serving in the South Korean military may provide information about the young adult male population in Korea.

AIM

To determine the relationship between chickenpox and atopic dermatitis (AD) in young adults over a period of 3 years.

METHODS

The computerized database of the Armed Forces Medical Command was examined to identify the number of reported cases of chickenpox, AD, and AD associated with chickenpox.

RESULTS

In total, 588 cases of chickenpox (183, 182 and 223 in the periods November 2004 to October 2005, November 2005 to October 2006, and November 2006 to October 2007, respectively) were reported. A greater number of patients were found to be infected with chickenpox in January and November, with fewer patients in August and September (P < 0.0001). Within the same periods, 1890, 2417 and 2779 patients diagnosed with AD were recorded in the Defense Medical Information System. Only 3 of 588 patients with chickenpox also had AD (0.5%).

CONCLUSION

In this population-based study, the epidemiological trend of chickenpox and AD over a period of 3 years within the military personnel of South Korea is shown.

Impact of universal varicella vaccination on 1-year-olds in Uruguay: 1997-2005

OBJECTIVE

Varicella vaccination was introduced at the end of 1999 into the Uruguayan immunisation schedule for children aged 12 months. Varilrix (Oka strain; GlaxoSmithKline Biologicals) has been the only vaccine used since then and coverage has been estimated to exceed 90% since the start of the universal varicella vaccination programme. We assessed the impact of the Uruguayan varicella vaccination programme during 2005, 6 years after its introduction.

METHODS

Information on hospitalisations was collected from the main paediatric referral hospital and information on medical consultations for varicella was collected from two private health insurance systems in Montevideo. The proportion of hospitalisations due to varicella and the proportion of ambulatory visits for varicella since the introduction of the vaccine were compared between 1999 and 2005 and 1997 and 1999 in the following age groups: <1 year, 1-4 years, 5-9 years and 10-14 years.

RESULTS

By 2005, the proportion of hospitalisations due to varicella among children, was reduced by 81% overall and by 63%, 94%, 73% and 62% in the <1, 1-4, 5-9 and 10-14 years age groups, respectively. The incidence of ambulatory visits for varicella among children was reduced by 87% overall and by 80%, 97%, 81% and 65% in the <1, 1-4, 5-9 and 10-14 years age groups, respectively.

CONCLUSIONS

The burden of varicella has decreased substantially in Uruguayan children since the introduction of the varicella vaccination, including those groups outside the recommended vaccination age. It is expected to decrease further as more cohorts of children are vaccinated and herd immunity increases.

Complete DNA sequences of two oka strain varicella-zoster virus genomes

Varicella-zoster virus (VZV) is a herpesvirus and is the causative agent of chicken pox (varicella) and shingles (herpes zoster). Active immunization against varicella became possible with the development of live attenuated varicella vaccine. The Oka vaccine strain was isolated in Japan from a child who had typical varicella, and it was then attenuated by serial passages in cell culture. Several manufacturers have obtained this attenuated Oka strain and, following additional passages, have developed their own vaccine strains. Notably, the vaccines Varilrix and Varivax are produced by GlaxoSmithKline Biologicals and Merck & Co., Inc., respectively. Both vaccines have been well studied in terms of safety and immunogenicity. In this study, we report the complete nucleotide sequence of the Varilrix (Oka-V(GSK)) and Varivax (Oka-V(Merck)) vaccine strain genomes. Their genomes are composed of 124,821 and 124,815 bp, respectively. Full genome annotations covering the features of Oka-derived vaccine genomes have been established for the first time. Sequence analysis indicates 36 nucleotide differences between the two vaccine strains throughout the entire genome, among which only 14 are involved in unique amino acid substitutions. These results demonstrate that, although Oka-V(GSK) and Oka-V(Merck) vaccine strains are not identical, they are very similar, which supports the clinical data showing that both vaccines are well tolerated and elicit strong immune responses against varicella.

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

OBJECTIVE

In 1995, the United States was the first country to introduce a universal 1-dose childhood varicella vaccination program. In 2006, the US varicella vaccine policy was changed to a routine 2-dose childhood program, with catchup vaccination for older children. The objective of this review was to summarize the US experience with the 1-dose varicella vaccination program, present the evidence considered for the policy change, and outline future challenges of the program.

METHODS

We conducted a review of publications identified by searching PubMed for the terms "varicella," "varicella vaccine," and "herpes zoster." The search was limited to US publications except for herpes zoster; we reviewed all published literature on herpes zoster incidence.

RESULTS

A single dose of varicella vaccine was 80% to 85% effective in preventing disease of any severity and >95% effective in preventing severe varicella and had an excellent safety profile. The vaccination program reduced disease incidence by 57% to 90%, hospitalizations by 75% to 88%, deaths by >74%, and direct inpatient and outpatient medical expenditures by 74%. The decline of cases plateaued between 2003 and 2006, and outbreaks continued to occur, even among highly vaccinated school populations. Compared with children who received 1 dose, in 1 clinical trial, 2-dose vaccine recipients developed in a larger proportion antibody titers that were more likely to protect against breakthrough disease and had a 3.3-fold lower risk for breakthrough disease and higher vaccine efficacy. Two studies showed no increase in overall herpes zoster incidence, whereas 2 others showed an increase.

CONCLUSIONS

A decade of varicella prevention in the United States has resulted in a dramatic decline in disease; however, even with high vaccination coverage, the effectiveness of 1 dose of vaccine did not generate sufficient population immunity to prevent community transmission. A 2-dose varicella vaccine schedule, therefore, was recommended for children in 2006. Data are inconclusive regarding an effect of the varicella vaccination program on herpes zoster epidemiology.

Impact of varicella vaccination on health care outcomes in Ontario, Canada: effect of a publicly funded program?

Varicella vaccines have been available for private purchase in Canada since 1998. Ontario introduced publicly funded varicella vaccination in 2004. We assessed the effects of private availability of varicella vaccines and subsequent implementation of a publicly funded vaccination program on varicella-related hospitalizations, emergency department (ED) use, and visits to physicians' offices in Ontario. Rates of hospitalizations, ED use, and office visits decreased 53% (95% CI, 48-58%), 43% (95% CI, 41-44%), and 45% (95% CI, 44-45%) after publicly funded vaccination, compared to only 9% (95% CI, 4-14%), 23% (95% CI, 22-24%), and 29% (95% CI, 28-29%) after private availability. Varicella vaccination is effective at reducing varicella-related health care use, with benefits extending beyond those who receive the vaccine. Publicly funded vaccination programs may be more effective than private vaccine availability.

Vaccine-era varicella epidemiology and vaccine effectiveness in a public elementary school population, 2002-2007

OBJECTIVE

We conducted ongoing varicella surveillance of public elementary school students to track changes in incidence from 2002 to 2007. In school year 2002-2003, we also conducted a retrospective cohort study to measure varicella vaccine effectiveness, assess relationships between risk factors for varicella in vaccine recipients (breakthrough varicella) identified in earlier studies, and assess the ability of school nurse surveillance to detect varicella cases.

PATIENTS AND METHODS

Varicella was defined as acute illness with maculo-papulo-vesicular rash without another apparent cause persisting >24 hours, regardless of previous episodes of the same or a similar illness. Using case data reported by school nurses, we described breakthrough varicella rates (percentage of vaccinated students with varicella), annual varicella-incidence rates (varicella cases per 100 public elementary school students), vaccine effectiveness, risk factors for breakthrough varicella, clinical characteristics of vaccinated and susceptible varicella patients, and sensitivity and positive predictive value of school nurse surveillance.

RESULTS

During school years 2002-2007, 502 elementary school students met the varicella case definition. Breakthrough varicella rates among exposed students ranged from 6% to 8% per school year; annual incidence rates ranged from 0.2% to 0.3% of public elementary school students; and varicella was more severe and lasted longer in susceptible than in vaccinated students. The positive predictive value of school nurse surveillance was 94%, and sensitivity was 90%. Vaccine effectiveness was 81%.

CONCLUSIONS

School nurse surveillance has both high positive predictive value and sensitivity and is a useful means of tracking varicella occurrence. Annual incidence rates of varicella are low. Vaccine effectiveness and breakthrough varicella rates are comparable to findings of other studies.

Compliance with vaccination recommendations for U.S. children

BACKGROUND

Official recommendations for the routine vaccination of U.S. children, made by the Advisory Committee on Immunization Practices (ACIP), specify the vaccines for administration, the number of doses that should be given, the age ranges for administration, the minimum ages at which doses are considered valid, the minimum intervals between doses within a series, and several additional vaccine-specific adjustments and exceptions. Federally reported estimates of vaccination coverage measure only compliance with the required number of doses; other recommendations are not routinely evaluated.

METHODS

Analysis of vaccination histories for 17,563 U.S. children aged 19-35 months from the 2005 National Immunization Survey.

MAIN OUTCOME MEASURES

Compliance with, and incremental impact of, each vaccination recommendation.

RESULTS

Estimated coverage was 72% for the standard vaccination series accounting for all recommendations, 9 percentage points lower than coverage based solely on counting doses. Overall, 19% of children were missing one or more doses, while 8% had received an invalid dose, and 9% were affected by other recommendations. The proportion of noncompliance due to missed doses versus other recommendations varied by state and by antigen.

CONCLUSIONS

Approximately 28% of children were not in compliance with the official vaccination recommendations. Missed doses accounted for approximately two thirds of noncompliance, with the remainder due to mis-timed doses and other requirements. Measuring compliance with all ACIP recommendations provides a valuable tool to assess and improve the quality of healthcare delivery and ensure that children and communities are optimally protected from vaccine-preventable diseases.

The impact of the varicella vaccination program on herpes zoster epidemiology in the United States: a review

Speculation that a universal varicella vaccination program might lead to an increase in herpes zoster (HZ) incidence has been supported by modeling studies that assume that exposure to varicella boosts immunity and protects against reactivation of varicella-zoster virus (VZV) as HZ. Such studies predict an increase in HZ incidence until the adult population becomes predominantly composed of individuals with vaccine-induced immunity who do not harbor wild-type VZV. In the United States, a varicella vaccination program was implemented in 1995. Since then, studies monitoring HZ incidence have shown inconsistent findings: 2 studies have shown no increase in overall incidence, whereas 1 study has shown an increase. Studies from Canada and the United Kingdom have shown increasing rates of HZ incidence in the absence of a varicella vaccination program. Data suggest that heretofore unidentified risk factors for HZ also are changing over time. Further studies are needed to identify these factors, to isolate possible additional effects from a varicella vaccination program. Untangling the contribution of these different factors on HZ epidemiology will be challenging.

Varicella among adults: data from an active surveillance project, 1995-2005

We report detailed population-based data on varicella among adults. In 2 US varicella active surveillance sites with high vaccine coverage among young children, the incidence of varicella among adults declined 74% during 1995-2005. A low proportion (3%) of adults with varicella had been vaccinated, with no improvement over the decade of program implementation, suggesting that the decline was likely secondary to herd-immunity effects. Compared with children, adults had more severe varicella in terms of both clinical presentation and frequency of complications. However, <30% of adults with varicella were treated with acyclovir. Among adolescents, illness severity was intermediate between that in children and adults. Varicella cases are preventable through vaccination. As we enter the second decade of the varicella vaccination program in the United States, we need to ensure that susceptible adolescents and adults are adequately protected from varicella by vaccination and that those who acquire varicella are appropriately treated with effective antiviral treatment.

Varicella disease among vaccinated persons: clinical and epidemiological characteristics, 1997-2005

Approximately 1 in every 5 children who receives 1 dose of varicella vaccine may develop varicella disease, also known as breakthrough disease, if exposed to varicella-zoster virus. Currently, in communities with high vaccination coverage, varicella cases mostly occur in vaccinated individuals. We report on the first population-based description of the clinical and epidemiological characteristics of varicella in populations with increasing vaccine coverage between 1997 and 2005. In vaccinated children 1-14 years of age, varicella was most often mild and modified; the atypical disease presentation may result in diagnostic challenges to health care providers. However, despite the generally mild nature of these cases, approximately 25% caused >50 lesions, and some resulted in serious complications similar to those occurring in unvaccinated individuals. Continued surveillance of the risk and characteristics of breakthrough disease will be needed, to monitor the effect of the new 2-dose vaccine recommendation for children.

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.

Humoral and cell-mediated immune responses in children and adults after 1 and 2 doses of varicella vaccine

Humoral and cell-mediated immune responses to varicella-zoster virus (VZV) have been evaluated after 1 and 2 doses of live attenuated varicella vaccine, Oka strain, in several studies. One dose of varicella vaccine, however, elicits detectable immune responses that are low and, in some cases, may be insufficient for complete protection against the virus after the normal decline in humoral and cell-mediated immunity with time. In contrast, immune responses after 2 doses are significantly higher and approximate the levels seen after natural disease. These investigations of vaccine-induced immunity suggest that 2 doses of VZV vaccine will better achieve the goals of the VZV vaccination program, by reducing the VZV burden of disease in childhood and preventing accumulation of young adults who are susceptible to or only partially protected from varicella.

Lack of association between age at varicella vaccination and risk of breakthrough varicella, within the Northern California Kaiser Permanente Medical Care Program

BACKGROUND

Varicella vaccine currently is recommended for children between 12 and 18 months of age. However, rates of breakthrough varicella have been reported to be higher among children vaccinated before 14 or 15 months of age and to increase with time since vaccination.

METHODS

An ongoing study at the Northern California Kaiser Permanente Medical Care Program is evaluating vaccine efficacy in 7585 children vaccinated with Varivax in 1995, when they were between 12 and 23 months of age. Cases of chickenpox are identified by telephone interviews with each child's parent(s) every 6 months. Mean age at varicella onset and mean time from vaccination to onset were calculated on the basis of age, in months, at vaccination. Logistic regression was used to test for trend, and the chi2 test was used to test for differences in rates of breakthrough varicella by age.

RESULTS

Over the first 8 years of the study, a total of 1161 cases of breakthrough varicella were reported, for an average rate of 21.7 cases/1000 person-years. Vaccine effectiveness was 83.6% at year 8. The rate of breakthrough varicella did not change for each additional month of age at vaccination (P = .864), and no difference in the rate of breakthrough varicella was found between children vaccinated at <15 months of age and those vaccinated at > or =15 months of age.

CONCLUSIONS

Our data do not show a difference in vaccine effectiveness with age at vaccination and thus support the current recommendations for initial vaccination between 12 and 18 months of age.

Varicella vaccination in Japan, South Korea, and Europe

The most extensive use of varicella vaccine has been in the United States and Canada, where it is universally recommended. However, a number of other countries now have recommendations for use of the vaccine, which has been expanding in Europe and Latin America. In this article, we review information concerning varicella vaccination in Japan, where the vaccine was first developed, and in South Korea and parts of Europe. Despite the worldwide availability of an efficient vaccine, varicella vaccination policy is highly variable from country to country. The recent development of a tetravalent vaccine against measles, mumps, rubella, and varicella could modify this variability in the future. It is evident that efforts to control varicella will spread gradually to all continents.

Varicella vaccination of immunocompromised children

BACKGROUND

Exposure of immunocompromised children to varicella often requires postexposure prophylaxis. Exposures requiring this management are often not recognized. Varicella can be a severe disease when it occurs in immunocompromised children, in spite of antiviral therapy. Varicella exposure and varicella in these children can also disrupt scheduled therapy for their underlying illness. Both postexposure prophylaxis and treatment of varicella are likely to be expensive and use significant medical resources. Numerous trials have been undertaken to vaccinate children who are immunocompromised by a variety of conditions and therapies that depress their immune function.

METHODS

Clinical trials of varicella vaccine administration to immunocompromised children that were reported since 1975 were identified in the Ovid medical database. Reports were selected for analysis and discussion on the basis of their completeness and the utility of their conclusions.

RESULTS

Vaccination before immune compromise is discussed as a strategy for some settings. The obstacles, potential opportunities, and success in varicella vaccination for immunocompromised children are separately analyzed for (1) children with leukemia and other malignancies, (2) human immunodeficiency virus-infected children, and (3) children with hematopoietic stem cell or solid-organ transplantation.

CONCLUSIONS

Vaccination before immune compromise is often successful, and the vaccine-induced response is usually partially or fully protective. In many treatment settings, it is possible to safely vaccinate once the level of immune suppression has been reduced. Targets for future research are outlined. A consensus conference should be undertaken to develop guidelines for the use of varicella vaccine in immunocompromised children.

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.

Risk of herpes zoster in adults immunized with varicella vaccine

A program of routine varicella vaccination of children 12-18 months of age, begun in the United States in 1995, has been very successful in reducing the incidence of varicella. Varicella-zoster virus (VZV), in both wild-type and live attenuated forms, is notable for its ability to produce latent infection of sensory neurons from which it can later reactivate to cause herpes zoster (HZ). Therefore, the effects of vaccination on this secondary VZV-related disease are important to consider; in practice, however, such studies are complicated by the typically long delay between acquisition of the virus and its reactivation. Studies of immunocompromised children have shown that vaccination is relatively protective against HZ in this highly vulnerable group. We now present long-term follow-up data on a group of individuals who received varicella vaccine as healthy young adults 10-26 years ago and who have been followed prospectively by means of active surveillance. Among some 2000 person-years of follow-up, 2 cases of HZ have occurred, for a rate of 1.00 case/1000 person-years. Overall, the incidence of HZ in this cohort, therefore, is similar to published data for the US population in the prevaccine era.

Varicella vaccine exposure during pregnancy: data from 10 Years of the pregnancy registry

BACKGROUND

The Pregnancy Registry for Varivax (Merck) was established to monitor for congenital varicella syndrome or other birth defects in the offspring of women who were exposed to varicella vaccine while pregnant.

METHODS

The registry receives voluntary reports from health care providers or consumers about women given the vaccine 3 months before or during pregnancy. Follow-up is conducted to obtain and classify pregnancy outcomes. All reports are evaluated for the presence of birth defects. Outcomes from prospectively reported pregnancy exposures are used to calculate rates and 95% confidence intervals.

RESULTS

From 17 March 1995 through 16 March 2005, 981 women were enrolled. Pregnancy outcomes were available for 629 prospectively enrolled women. Among the 131 live births to varicella-zoster virus-seronegative women, there was no evidence of congenital varicella syndrome (rate, 0% [95% confidence interval [CI], 0%-6.7%]), and major birth defects were observed in 3 infants (rate, 3.7% [95% CI, 0.8%-10.7%]).

CONCLUSIONS

Although the numbers of exposures are not sufficient to rule out a very low risk, data collected in the pregnancy registry to date do not support a relationship between the occurrence of congenital varicella syndrome or other birth defects and varicella vaccine exposure during pregnancy.

Laboratory diagnosis and characteristics of breakthrough varicella in children

The atypical features of varicella in vaccinated persons (breakthrough varicella [BTV]) present diagnostic challenges. We examined varicella-zoster virus (VZV) polymerase chain reaction (PCR) and immunoglobulin (Ig) M and IgG serologic test results for confirming BTV cases. Among 33 vaccinated children with varicella-like rash, we identified wild-type VZV in 58% overall and in 76% of those with adequate tissue specimens; no vaccine-type virus was found. Of the 12 subjects with PCR-confirmed BTV and acute-phase serum samples, 9 had detectable IgM, and all had highly elevated acute-phase IgG titers. Six subjects with negative PCR results had lower IgG titers and negative IgM results. Although PCR is the preferred method for laboratory confirmation of BTV, a positive serum varicella IgM test result should also be considered to be diagnostic in a suspected BTV case; however, a negative IgM test result cannot be used to rule out the diagnosis. The value of highly elevated IgG titers needs further evaluation. Larger studies are needed to confirm these results.

Knowledge, attitudes, and practices regarding varicella vaccination among health care providers participating in the varicella active surveillance project, Antelope Valley, California, 2005

Knowledge, attitudes, and practices regarding varicella vaccination and disease were assessed among health care providers participating in the Varicella Active Surveillance Project in Antelope Valley, California, in 2005. Compared with those of a similar survey conducted in 1999, results suggest a reduction in concerns about vaccine safety and efficacy. Routine assessment of adolescents for varicella susceptibility was reported by 87% of respondents, but only 42% reported routine assessment of adults. Several respondents were unaware that disease in a vaccinated person is infectious, and some did not know the vaccination recommendations pertaining to susceptible health care workers, suggesting a need for provider education on these issues.

Safety of varicella vaccine after licensure in the United States: experience from reports to the vaccine adverse event reporting system, 1995-2005

Widespread use of varicella vaccine in the United States could enable detection of rare adverse events not identified previously. We reviewed data from 1995 to 2005 from the Vaccine Adverse Event Reporting System, including data from laboratory analyses, to distinguish adverse events associated with wild-type varicella-zoster virus (VZV) versus those associated with vaccine strain. Almost 48 million doses of varicella vaccine were distributed between 1995 and 2005. There were 25,306 adverse events reported (52.7/100,000 doses distributed); 5.0% were classified as serious (2.6/100,000 doses distributed). Adverse events associated with evidence of vaccine-strain VZV included meningitis in patients with concurrent herpes zoster. Patients with genetic predispositions may rarely have disease triggered by receipt of varicella vaccine. Overall, serious adverse events reported after varicella vaccination continue to be rare and must be considered relative to the substantial benefits of varicella vaccination. Ongoing safety surveillance and further studies may shed light on some of the hypothesized associations.