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

One dose of varicella vaccine does not prevent school outbreaks: is it time for a second dose?

OBJECTIVES

The implementation of a routine childhood varicella vaccination program in the United States in 1995 has resulted in a dramatic decline in varicella morbidity and mortality. Although disease incidence has decreased, outbreaks of varicella continue to be reported, increasingly in highly vaccinated populations. In 2000, a varicella vaccination requirement was introduced for kindergarten entry in Arkansas. In October 2003, large numbers of varicella cases were reported in a school with high vaccination coverage. We investigated this outbreak to examine transmission patterns of varicella in this highly vaccinated population, to estimate the effectiveness of 1 dose of varicella vaccine, to identify risk factors for vaccine failure, and to implement outbreak control measures.

METHODS

A retrospective cohort study involving students attending an elementary school was conducted. A questionnaire was distributed to parents of all of the students in the school to collect varicella disease and vaccination history; parents of varicella case patients were interviewed by telephone. A case of varicella was defined as an acute, generalized, maculopapulovesicular rash without other apparent cause in a student or staff member in the school from September 1 to November 20, 2003. Varicella among vaccinated persons was defined as varicella-like rash that developed >42 days after vaccination. In vaccinated persons, the rash may be atypical, maculopapular with few or no vesicles. Cases were laboratory confirmed by polymerase chain reaction, and genotyping was performed to identify the strain associated with the outbreak.

RESULTS

Of the 545 students who attended the school, 88% returned the questionnaire. Overall varicella vaccination coverage was 96%. Forty-nine varicella cases were identified; 43 were vaccinated. Three of 6 specimens tested were positive by polymerase chain reaction. The median age at vaccination of vaccinated students in the school was 18 months, and the median time since vaccination was 59 months. Forty-four cases occurred in the East Wing, where 275 students in grades kindergarten through 2 were located, and vaccination coverage was 99%. In this wing, varicella attack rates among unvaccinated and vaccinated students were 100% and 18%, respectively. Vaccine effectiveness against varicella of any severity was 82% and 97% for moderate/severe varicella. Vaccinated cases were significantly milder compared with unvaccinated cases. Among the case patients in the East Wing, the median age at vaccination was 18.5 and 14 months among non-case patients. Four cases in the West Wing did not result in further transmission in that wing. The Arkansas strains were the same as the common varicella-zoster virus strain circulating in the United States (European varicella-zoster virus strain).

CONCLUSIONS

Although disease was mostly mild, the outbreak lasted for approximately 2 months, suggesting that varicella in vaccinated persons was contagious and that 99% varicella vaccination coverage was not sufficient to prevent the outbreak. This investigation highlights several challenges related to the prevention and control of varicella outbreaks with the 1-dose varicella vaccination program and the need for further prevention of varicella through improved vaccine-induced immunity with a routine 2-dose vaccination program. The challenges include: 1-dose varicella vaccination not providing sufficient herd immunity levels to prevent outbreaks in school settings where exposure can be intense, the effective transmission of varicella among vaccinated children, and the difficulty in the diagnosis of mild cases in vaccinated persons and early recognition of outbreaks for implementing control measures. The efficacy of 2 doses of varicella vaccine compared with 1 dose was assessed in a trial conducted among healthy children who were followed for 10 years. The efficacy for 2 doses was significantly higher than for 1 dose of varicella vaccine. This higher efficacy translated into a 3.3-fold lower risk of developing varicella >42 days after vaccination in 2- vs 1-dose recipients. Of the children receiving 2 doses, 99% achieved a glycoprotein-based enzyme-linked immunosorbent assay level of > or =5 units (considered a correlate of protection) 6 weeks after vaccination compared with 86% of children who received 1 dose. The 6-week glycoprotein-based enzyme-linked immunosorbent assay level of > or =5 units has been shown to be a good surrogate for protection from natural disease. Ten years after the implementation of the varicella vaccination program, disease incidence has declined dramatically, and vaccination coverage has increased greatly. However, varicella outbreaks continue to occur among vaccinated persons. Although varicella disease among vaccinated persons is mild, they are contagious and able to sustain transmission. As a step toward better control of varicella outbreaks and to reduce the impact on schools and public health officials, in June 2005, the Advisory Committee on Immunization Practices recommended the use of a second dose of varicella vaccine in outbreak settings. Early recognition of outbreaks is important to effectively implement a 2-dose vaccination response and to prevent more cases. Although the current recommendation of providing a second dose of varicella vaccine during an outbreak offers a tool for controlling outbreaks, a routine 2-dose recommendation would be more effective at preventing cases. Based on published data on immunogenicity and efficacy of 2 doses of varicella vaccine, routine 2-dose vaccination will provide improved protection against disease and further reduce morbidity and mortality from varicella.

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.

Varicella-related hospitalization and emergency department visit rates, before and after introduction of varicella vaccine, among white and black children in Hamilton County, Ohio

OBJECTIVE

The American Academy of Pediatrics recommended routine use of varicella vaccine in pediatric practice in 1995. We examined the impact of varicella immunization on population-based rates of pediatric varicella-related hospitalizations and emergency department (ED) visits in the years before and after introduction of varicella vaccine.

STUDY DESIGN

Discharge data for hospitalizations and ED encounters from 1990 through 2003 were queried for patients <20 years of age with varicella International Classification of Diseases, Ninth Revision, Clinical Modification codes (052.0-052.9) in any diagnostic position. Addresses were geocoded for identification of Hamilton County, Ohio, residents. Rates were calculated according to year, age, and race, with census estimates.

RESULTS

During the 14-year study period, there were 3983 incident varicella cases; 335 patients were hospitalized and 3833 were treated only in the ED. The rate of varicella-related hospitalizations decreased from 15.7 cases per 100,000 population to 5.5 cases per 100,000 population between the prevaccine period (1990-1995) and the postvaccine period (1996-2003); varicella-related ED use decreased from 178.2 cases per 100,000 population to 61.2 cases per 100,000 population. In the prevaccine period, hospitalization and ED visit rates were significantly higher for black children than for white children. In the postvaccine period, hospitalization rates did not differ according to race but ED visit rates remained significantly higher for black children, compared with white children.

CONCLUSIONS

Varicella-related hospitalization and ED visit rates decreased significantly for both white and black children in Hamilton County, Ohio, after the introduction of varicella vaccine, and the racial disparity found before licensure decreased after licensure.

Motifs d'hospitalisation des patients atteints de varicelle dans un établissement pédiatrique parisien : évolution entre 1990 et 2001

AIMS OF STUDY

To describe the characteristics of paediatric varicella in patients admitted through the emergency department (ED) of the Armand-Trousseau Children hospital in Paris and the evolution of the causes of admission during the study period.

STUDY DESIGN

Retrospective longitudinal cohort study from March 1990 to February 2001.

RESULTS

One hundred and eight children were hospitalized for varicella during these 11 years. Sixty per cent were under 2 years of age and all but one were immunocompetent. The first cause of admission was the presence of at least 1 complication (83,3%) classified as: cutaneous (34%), digestive (19,8,%), respiratory (17,6%), neurological (15,3%) and ENT complications (8,8%). Over 11 years, the rate of overall complications remained stable but there was an important increase in varicella cases admitted through the ED mainly due to increase in cutaneous superinfections.

CONCLUSION

These data confirm the potential severity of varicella and underline the emerging problem of increasing cutaneous complications. Additional studies are necessary to address this phenomenon and to determine optimal prophylactic measures.

Uptake of varicella vaccination among young children in the United States: a success story in eliminating racial and ethnic disparities

OBJECTIVE

To examine uptake of varicella vaccine, a live attenuated vaccine licensed in 1995 and recommended in 1996 for routine vaccination of US children 12 to 18 months of age.

METHODS

Data were for 178,616 children (19-35 months of age) and were collected in the 1997 to 2004 National Immunization Survey. The main outcome measures were estimated varicella vaccine coverage from 1997 to 2004, coverage among susceptible children (ie, those without a history of varicella disease), racial/ethnic disparities, risk factors for nonvaccination, missed opportunities to vaccinate simultaneously with other recommended vaccines, and projected increases in coverage after elimination of missed opportunities for simultaneous vaccination.

RESULTS

Varicella vaccine coverage rates increased from 26% in 1997 to 87% in 2004. State-specific coverage rates increased 44 to 80 percentage points and were >80% in 42 states and >90% in 13 states by 2004. Coverage among susceptible children increased from 62% in 1999 to 88% in 2004. From 1998 onward, no statistically significant differences in coverage were found between white and black children, whereas Hispanic children had higher coverage rates than white children in 1998 to 2001 and 2004. Risk factors for undervaccination included living in the Midwest region, living in a household with >1 child, living in nonmetropolitan areas, living below the poverty level, having a mother who did not have a college degree, and having public providers. If missed opportunities for simultaneous vaccination had been eliminated, then coverage rates would have increased from 58% to 94% in 1999 and from 87% to 96% in 2004.

CONCLUSIONS

Uptake of varicella vaccine has been steady and is an example of successful elimination of racial and ethnic disparities. Additional focus should be placed on reducing missed opportunities for simultaneous vaccination, improving coverage in rural areas and the Midwest region, and closing remaining gaps related to maternal education, provider type, and multiple-children households.

A combination measles, mumps, rubella, and varicella vaccine (ProQuad) given to 4- to 6-year-old healthy children vaccinated previously with M-M-RII and Varivax

BACKGROUND

In the United States, children receive primary doses of M-M-RII (Merck & Co, Inc, West Point, PA) and Varivax (Merck & Co, Inc) beginning at 12 months, often at the same health care visit. Currently a second dose of M-M-RII is given to 4- to 6-year-old children, to increase vaccination rates and to reduce the number of individuals without detectable antibodies. A second dose of a varicella-containing vaccine may result in similar benefits.

OBJECTIVES

To demonstrate that ProQuad (measles, mumps, rubella, and varicella virus vaccine live; Merck & Co, Inc) may be given in place of a second dose of M-M-RII or second doses of M-M-RII and Varivax for 4- to 6-year-old children.

METHODS

Four- to 6-year-old children who had been immunized previously with M-M-RII and Varivax were assigned randomly to receive either ProQuad and placebo (N = 399), M-M-RII and placebo (N = 195), or M-M-RII and Varivax (N = 205) and were then monitored for safety and immunogenicity.

RESULTS

ProQuad was generally well tolerated. Similarity (noninferiority) was demonstrated in postvaccination antibody responses to measles, mumps, and rubella between recipients of ProQuad and all recipients of M-M-RII and in responses to varicella between recipients of ProQuad and recipients of Varivax. Postvaccination seropositivity rates for antibodies against all 4 viruses were nearly 100% in all 3 groups. Small fold increases were observed for measles, mumps, and rubella antibody titers. In contrast, substantial boosts in varicella antibody titers were observed among recipients of a second dose of varicella vaccine, administered as ProQuad or Varivax.

CONCLUSIONS

ProQuad may be used in place of a second dose of M-M-RII or second doses of M-M-RII and Varivax for 4- to 6-year-old children.

Modelling the impact of vaccination on the epidemiology of varicella zoster virus in Australia

OBJECTIVE

To model the impact of universal varicella vaccination in Australia.

METHODS

The results of an Australia-wide serosurvey for varicella zoster virus (VZV) immunity were used to parameterise realistic, age-structured deterministic models (RAS) developed by Brisson and colleagues. We examined the impact of a vaccination program for one-year-olds alone, and with a catch-up campaign for 11-year-olds, on the incidence of varicella and zoster, using Australia's population structure. Morbidity was then determined by calculating the number of hospital in-patient days.

RESULTS

Infant vaccination is predicted to reduce the incidence of varicella. However, zoster incidence is expected to increase initially, assuming exposure to varicella boosts immunity to zoster. Accumulated morbidity from both varicella and zoster is predicted to remain above that expected without vaccination for the first 70 years of an infant program (assuming 90% coverage with boosting for 20 years). However, after 70 years the net health savings from vaccination are predicted to increase substantially.

CONCLUSIONS AND IMPLICATIONS

Infant vaccination is expected to be a successful long-term commitment to reducing morbidity associated with VZV infection in Australia.

Seroprevalence of varicella in the French population

OBJECTIVES

To assess the age-specific seroprevalence of varicella in the French population and to explore age-adjusted differences according to gender and geographic region.

METHODS

Data were obtained from 1257 randomly selected, frozen serum samples, from subjects 1-30 years of age, that were sent to the Pasteur-Cerba laboratory in November 2003 to January 2004 for the following clinical indications: allergies, respiratory infections, herpes virus infections excluding varicella and endocrinologic tests. IgG concentrations were tested with an indirect enzyme immunoassay. Statistical analyses included use of locally weighted, scatterplot smoothers.

RESULTS

Age-specific seroprevalence of varicella increased by >6-fold between 1 and 8 years of age, ie, from 15.0% (95% confidence interval, 8.6-23.5%) for subjects 1-2 years of age to 89.0% (95% confidence interval, 81.0-94.3%) for those 7-8 years of age. The smoothed curve of age-specific seroprevalence suggested that the steepest rate of increase occurred between 1 and 8 years of age, followed by a considerable slowing in the rate of increase, reaching a prevalence of approximately 95% by age 30. Varicella seroprevalence rates were similar for the samples referred for the 4 clinical indications, as follows: allergies, 76.2%; respiratory infections, 74.0%; herpes virus infections excluding varicella, 73.3%; endocrinologic tests, 73.7% (P = 0.84).

CONCLUSIONS

Most varicella-zoster virus infections occur during early childhood. Seroprevalence rates reach approximately 50% by 4 years of age and approximately 90% by 8 years. Therefore, the best strategy to reduce the prevalence of wild-type varicella-zoster virus in the French population would be to immunize children 12-18 months of age, as is currently performed in the United States.

Immunogenicity and safety of two doses of tetravalent measles-mumps-rubella-varicella vaccine in healthy children

BACKGROUND

Combination vaccines against common childhood diseases are widely used, provide an improved coverage, are more convenient and are more cost-effective than multiple injections. We conducted a study to evaluate the safety and immunogenicity of a combined measles-mumps-rubella-varicella (MMRV) candidate vaccine in comparison with the separate administration of licensed measles-mumps-rubella (MMR; Priorix) and varicella (V; Varilrix) vaccines.

METHODS

Healthy children 12-18 months of age received 2 doses of MMRV vaccine (3 lots) 6-8 weeks apart (MMRV group) or 1 dose of MMR vaccine administered concomitantly with 1 dose of varicella vaccine, followed by a second dose of MMR at 6-8 weeks later (MMR+V group). Local symptoms (redness, pain and swelling) were recorded for 4 days after vaccination, and fever (any, axillary temperature > or =37.5 degrees C or rectal temperature > or =38.0 degrees C; grade 3, axillary temperature >39.0 degrees C or rectal temperature >39.5 degrees C) was monitored daily for 15 days. Other adverse events were monitored for 6 weeks.

RESULTS

A total of 494 children were vaccinated (371 in the MMRV group and 123 in the MMR+V group. Two doses of MMRV vaccine were at least as immunogenic as 2 doses of MMR and 1 dose of varicella vaccine. After the second dose, all children had seroconverted to measles, rubella and varicella in both vaccine groups, and 98% versus 99% had seroconverted to mumps in the MMRV versus the MMR+V group, respectively. The MMRV vaccine did not induce an increased local or general reactogenicity compared with the separate administration, although a higher incidence of low grade fever was seen after the first dose in the MMRV group (67.7% after MMRV versus 48.8% after MMR+V; P < 0.05), this was not observed for grade 3 fever (11.6% after MMRV versus 10.6% after MMR+V; P = 0.87). After the second dose, no differences in incidence of fever were found in either MMRV or MMR+V groups.

CONCLUSION

Administration of 2 doses of the combined MMRV vaccine was as immunogenic and well-tolerated as separate injections of MMR and varicella vaccine.

Universal varicella vaccination: efficacy trends and effect on herpes zoster

In 1995, the Varicella Active Surveillance Project (VASP) was established in Antelope Valley (California), a geographically distinct high-desert community of 300,000 residents, as one of three sites in the nation in a cooperative agreement with the Centers for Disease Control and Prevention (CDC) to collect baseline demographic and clinical data and to monitor trends in varicella (chickenpox) following introduction of varicella vaccine. Herpes zoster (shingles) was added to the active surveillance January 1, 2000. The universal varicella program has proven effective in terms of reducing the number of reported verified varicella cases by 85%, from 2,934 in 1995 to 412 in 2002. Prior to this dramatic reduction, immunologic boosting due to exogenous exposures to wild-type varicella-zoster virus (VZV) in the community (1) caused mean serum anti-VZV levels among vaccines to increase with time after vaccination and (2) served as a mechanism that helped suppress the reactivation of herpes zoster (HZ), especially among individuals with a previous history of wild-type varicella. That immunologic boosting might play a significant role in both varicella and the closely related HZ epidemiology is evidenced by (1) a decline in vaccine efficacy by over 20%, from 95.7% (95% C.I., 82.7% to 98.9%) in 1999 to 73.9% (95% C.I., 57.9% to 83.8%) in 2001 and (2) an unexpectedly high cumulative (2000 to 2003) true incidence rate of 223 (95% C.I. 180-273) per 100,000 person-years (p-y) among children <10 years old with a previous history of varicella. Because capture-recapture methods demonstrate a likely lower bound of 50% underreporting, the actual rate is likely double or 446 per 100,000 p-y, approaching the HZ rate reported among older adults. Other recent studies based on VASP data have mitigated against discovery of the above trends that challenge several initial assumptions inherent to the universal varicella program, namely, (1) a single dose confers long-term immunity and (2) there is no immunologically mediated link between varicella and HZ incidence. As vaccinated children replace those with a prior history of wild-type varicella in the <10 age group, increasing HZ incidence among this cohort will be of less concern in the near future. However, previous scientific studies, including the present preliminary results from active surveillance indicate that HZ may be increasing among adults. It may be difficult to design booster interventions that are cost-effective and meet or exceed the level of protection provided by immunologic boosting that existed naturally in the community in the prelicensure era.

Chickenpox complications in Saudi Arabia: Is it time for routine varicella vaccination?

INTRODUCTION

Varicella zoster (chickenpox) infection is a common and benign disease of childhood. The predominance of uncomplicated cases in children tends to overshadow the morbidity associated with severe cases and the resultant hospitalization.

OBJECTIVE

The objective was to establish the complication rate of chickenpox in the Saudi National Guard population over a 2(1/2)-year period.

METHODS

All reported cases of chickenpox at the King Abdulaziz Medical City, Riyadh were prospectively followed for development of complications during the period between 1 June 2001 and 30 December 2003.

RESULTS

A total of 3802 cases of chickenpox were reported and followed during the acute illness phase. The majority of cases, 2984 (78%), occurred in children less than 15 years of age. Among all chickenpox cases, 78 (2%) required hospitalization, and 50 patients developed 58 (1.5%) complications. Skin and soft tissue infections were the most common complications, 20 (34%), followed by pneumonia in 16 (28%), bacteremia in six (10%), encephalitis in four (7%) and necrotizing fasciitis in four (7%). Complications were less common in children (36/2984, 1.2%) as compared to adults (14/818, 1.7%) (p = 0.26). However, pneumonia (p = 0.03) and hospitalization (p = 0.004) were more common in adults as compared to children. The overall fatality rate was 0.05%; two patients died, one aged two months the other 28 years.

CONCLUSION

These data provide a baseline for morbidity and mortality from chickenpox, and further support the inclusion of varicella vaccine in the routine childhood immunization program in Saudi Arabia.

Uptake of varicella vaccine—a cross sectional survey of parental attitudes to nationally recommended but unfunded varicella immunisation

The aim of this study was to assess the uptake of varicella vaccine in South Australian children under circumstances where varicella immunisation is recommended, but is not funded by Government. The study examined the main reasons that determined a parent's decision whether or not to have their child immunised with varicella vaccine. A cross-sectional survey was conducted by Computer Aided Telephone Interviews (CATI) in June 2004. Data were obtained from 613 households containing 1148 children aged from birth to 17 years of age. Statistical analyses were performed using data weighted to the South Australian population. Six hundred and eighty children (55.7%) had a history of varicella infection and 446 children (42.0%) had received varicella vaccine (weighted data). The most common reasons cited for not having children immunised included lack of knowledge about the vaccine and cost. One year after inclusion of varicella vaccine in the Australian Standard Vaccination Schedule there is evidence of incomplete coverage in children in South Australia due to absence of government funding for vaccine provision.

Is Europe ready to embrace a policy of universal varicella vaccination?

For the first time, a live attenuated varicella vaccine with an indication for universal vaccination is licensed in all EU countries. It is now time to consider whether in Europe there should be widespread vaccination against varicella to prevent this common and highly infectious disease. Increasing numbers of countries are adopting vaccination programmes against the disease. In those countries where a routine vaccination policy has been adopted, the success of the vaccine has been significant. The USA, which prior to the launch of a universal vaccination programme in 1995 had 4 million cases of varicella per year, has seen a dramatic reduction in varicella morbidity and mortality rates. A universal varicella vaccination policy is an option that needs to be considered for Europe not only in medical terms but also because it would be socially and economically appropriate.

Varicella vaccination in Australia

Varicella zoster virus (VZV) causes both chickenpox and herpes zoster and is responsible for a significant disease burden, including hospitalizations and deaths, in Australian children and adults. Varicella vaccine has been available in Australia for 5 years; however, from November 2005, it will be funded for use in all susceptible children at 18 months and 10-13 years of age under the National Immunisation Program. Experience with universal varicella vaccination of children in the USA over the last 10 years has shown that the vaccine is safe and highly effective in reducing varicella-related disease. This review summarizes the epidemiology of VZV-related disease in Australia, the use of varicella vaccine and the international experience with vaccine efficacy and safety. The potential impact of varicella vaccination on the incidence of herpes zoster is also discussed.

Varicella vaccination of children in the United States: assessment after the first decade 1995-2005

Live attenuated varicella vaccine (strain Oka) was approved for administration to healthy children in the United States in 1995. Over the past 10 years, varicella vaccine has been given to millions of children, usually at ages between 12 and 18 months. In states such as California, Michigan, and Texas, there has been a marked decline in the number of reported cases of varicella. Furthermore, there has been a 75% decrease in varicella-related hospitalizations across the United States, as well as a similar decrease in the number of deaths caused by complications of chickenpox. The main unanticipated result has been a growing number of outbreaks of varicella among immunized children ("breakthrough varicella"). The most cited risk factors for breakthrough varicella include the following: (1) 3-5-year interval since immunization and (2) immunization at the youngest ages, especially 12 months. Explanations for breakthrough varicella include a lessened immune response among the youngest recipients of the vaccine. Another possibility is genetic variation among circulating VZV strains. VZV strains can be separated into two geographic clades called European/North American and Asian, based on single nucleotide polymorphisms. Two mutant North American strains have been isolated from patients in the last 10 years. Several genomic differences between Oka vaccine strain and other strains have also been identified, including one site at the DNA origin of replication. Since breakthrough disease among vaccine recipients appears to be more common in the United States than in Japan, further comparisons between the varicella vaccination programs in Japan and the United States are warranted. In addition, data from varicella vaccination programs in Europe should provide further insight into the effectiveness of varicella vaccination in different geographic and ethnic populations.

Recent steroid therapy increases severity of varicella infections in children with acute lymphoblastic leukemia

OBJECTIVE

The varicella-zoster virus (VZV) continues to be a dangerous pathogen to immunocompromised children. Children with acute lymphoblastic leukemia (ALL) are treated with intermittent steroid therapy. This study was undertaken to examine the relationship between steroid therapy for ALL and severity of varicella infection.

METHODS

We performed a retrospective review of patients who were on Pediatric Oncology Group Protocol 9201 and had a history of varicella infection. Pediatric Oncology Group 9201 is a phase III study for the treatment of children with lesser risk ALL diagnosed between 1992 and 1999. Cases of varicella were coded 1 to 5 on the basis of severity: grade 1 caused minimal to no symptoms, grade 2 caused mild to moderate symptoms that did not require hospitalization, grade 3 caused symptoms severe enough to require hospitalization and intravenous acyclovir, grade 4 caused severe disease that had complications or that required intensive care, and grade 5 resulted in death.

RESULTS

Of 697 enrolled patients, 110 (15.8%) developed primary varicella; 59% of these were male. For analysis, disease grade was dichotomized into nonsevere (grades 1 and 2) and severe (grades 3, 4, and 5). Of the 110 patients, 56 had nonsevere disease; 54 had severe disease, including 2 deaths. Of the patients whose varicella was diagnosed within 3 weeks of receipt of prednisone, 70% had severe infection, whereas only 44% of those who had not received prednisone within 3 weeks had severe infection. The odds ratio for having a severe infection within 3 weeks of prednisone versus >3 weeks is 2.9 (95% confidence interval: 1.1-7.9). By multivariate analysis, older age at ALL diagnosis, years from ALL diagnosis to VZV diagnosis, and VZV diagnosis within the 4-week period of interest (during or within 3 weeks of prednisone therapy) all were independently associated with an increased risk for severe infection.

CONCLUSIONS

This study represents the largest study to date of varicella in children with ALL and provides convincing evidence that prednisone therapy during the VZV incubation period significantly increases the risk for developing severe varicella infection. In addition, older age is associated with more severe infection. Despite the varicella vaccine and a dropping incidence of primary infections, VZV remains a dangerous pathogen for pediatric patients with ALL. With the possible exception of induction therapy, patients who are on ALL therapy and are exposed to varicella should have steroid therapy delayed until after the VZV incubation period. These findings may have implications for other diseases that are treated with corticosteroids.

[Immunisation against varicella]

Two vaccines against varicella are now being licensed in France, both deriving from the Oka strain. Seroconversion has been obtained in almost 100% of the cases after one dose in toddlers and children, and two doses in adolescents and adults. Efficacy has been mainly established from the US experience, where a universal immunisation programme of children aged > 12 months with a catch-up for susceptible adolescents and adults was begun in 1995. The incidence of varicella has decreased by about 85% over all age groups. The safety of the vaccine is good, and most adverse events are represented by fever, reactions at the injection site and varicella-like rashes. For the time being, France has adopted restrictive recommendations for the use of this vaccine because of uncertainties with respect to the duration of protection, a shift of the disease towards older age and the potential increase of the incidence of herpes-zoster.

Sudden death in childhood due to varicella pneumonia: a forensic case report with clinical implications

Varicella (chickenpox) is one of the most frequent highly infectious diseases in childhood. It is caused by varicella-zoster virus. Lethal complications are rare. Focused on histological findings, we present a case of a sudden unexpected death of an otherwise healthy 18-month-old girl due to varicella-induced pneumonia. The histological and immunohistochemical investigations of the lung tissue revealed typical findings of a varicella pneumonia: haemorrhagic and necrotic nodules, intra-alveolar fibrin, numerous neutrophilic granulocytes, lymphocytes, plasmacells, macrophages, multinucleated giant cells and hyaline membranes. Varicella-related deaths are preventable by vaccine. To prevent complications and lethal outcome of varicella as reported here, the recommendations concerning vaccination against varicella must be taken into account in paediatric practice.

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

BACKGROUND

The 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.

METHODS

In 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.

RESULTS

Between 1998 and 2003, varicella incidence declined from 16.5/1,000 to 3.5/1,000 (79%) overall with > or = 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.

CONCLUSION

As 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.

Cost-benefit analysis of universal varicella vaccination in the U.S. taking into account the closely related herpes-zoster epidemiology

Many models concur that universal varicella vaccination of children is beneficial from the perspective of reducing societal costs. Yet, the majority of such cost analyses have been modeled under the assumption that varicella vaccination has no adverse effect on the closely related herpes-zoster (HZ) epidemiology. Historical models have assumed that asymptomatic endogenous reactivation is the chief mechanism of boosting that suppresses the reactivation of HZ and that immunity wanes due to the aging process. Recent studies suggest instead that periodic exogenous exposures to wild-type varicella are the predominant factor influencing the curve of increasing HZ incidence rate with advancing age among individuals <50, after which an age-related decline dominates in the elderly. Based on a realistic age-structured model, we compare differences in outcomes of the number of HZ cases and direct medical costs associated with the population existing in 2000 and as it ages (according to the mortality given in the 2000 U.S. census) during the following 50 years with and without implementation of universal varicella vaccination. Under universal varicella vaccination, we assume that 15 years post-licensure, the boosting mechanism known as asymptomatic endogenous reactivation principally serves to limit HZ incidence to 550 per 100,000 person-years in unvaccinated individuals <50 with a previous history of natural varicella--since there has been a vaccine-induced decline in exogenous boosting. We estimate universal varicella vaccination has the impact of an additional 14.6 million (42%) HZ cases among adults aged <50 years during a 50 year time span at a substantial cost burden of 4.1 billion US dollars or 80 million US dollars annually utilizing an estimated mean healthcare provider cost of 280 US dollars per HZ case.

Immunizations in the United States: a rite of passage

Today, vaccination is a cornerstone of pediatric preventive health care and a rite of passage for nearly all of the approximately 11,000 infants born daily in the United States. This article reviews the US immunization program with an emphasis on its role in ensuring that vaccines are effective, safe, and available and highlights several new vaccines and recommendations that will affect the health of children and adolescents and the practice of pediatric medicine in future decades.

Vaccine effectiveness during a varicella outbreak among schoolchildren: Utah, 2002-2003

OBJECTIVES

In the context of a chickenpox outbreak involving 2 Utah elementary schools, we conducted an investigation to assess vaccine effectiveness, describe illness severity, and examine risk factors for breakthrough varicella (ie, varicella in those who have been vaccinated).

METHODS

All parents were asked to complete a questionnaire about their child's medical history. Parents of children with recent varicella were interviewed, and vaccination records were verified. Lesions were submitted for polymerase chain reaction testing.

RESULTS

Questionnaires were returned for 558 (93%) of 597 students in school A and 924 (97%) of 952 students in school B. A total of 83 schoolchildren (57 unvaccinated and 26 vaccinated) had varicella during the October 2002 through February 2003 outbreak period. An additional 17 cases occurred among household contacts, including infants and adults. Polymerase chain reaction analysis recovered wild-type varicella. Vaccine effectiveness was 87%. With 1 notable exception, vaccinated children tended to have milder illness. Risk factors for breakthrough varicella included eczema, vaccination > or =5 years before the outbreak, and vaccination at < or =18 months of age. Restricting analysis to children vaccinated > or =5 years before the outbreak, those vaccinated at < or =18 months of age were more likely to develop breakthrough varicella (relative risk: 9.3; 95% confidence interval: 1.3-68.9).

CONCLUSIONS

The vaccine, administered by >100 health care providers to 571 children during a 7-year time period, was effective. Risk factors for breakthrough varicella suggest some degree of biological interaction between age at vaccination and time since vaccination.

The economic value of childhood varicella vaccination in France and Germany

OBJECTIVE

To determine the economic impact of childhood varicella vaccination in France and Germany.

METHODS

A common methodology based on the use of a varicella transmission model was used for the two countries. Cost data (2002 per thousand) were derived from two previous studies. The analysis focused on a routine vaccination program for which three different coverage rates (CRs) were considered (90%, 70%, and 45%). Catch-up strategies were also analyzed. A societal perspective including both direct and indirect costs and a third-party payer perspective were considered (Social Security in France and Sickness Funds in Germany).

RESULTS

A routine vaccination program has a clear positive impact on varicella-related morbidity in both countries. With a 90% CR, the number of varicella-related deaths was reduced by 87% in Germany and by 84% in France. In addition, with a CR of 90%, routine varicella vaccination induces savings in both countries from both societal (Germany 61%, France 60%) and third-party payer perspectives (Germany 51%, France 6.7%). For lower CRs, routine vaccination remains cost saving from a third-party payer perspective in Germany but not in France, where it is nevertheless cost-effective (cost per life-year gained of 6521 per thousand in the base case with a 45% CR).

CONCLUSION

Considering the impact of vaccination on varicella morbidity and costs, a routine varicella vaccination program appears to be cost saving in Germany and France from both a societal and a third-party payer perspective. For France, routine varicella vaccination remains cost-effective in worst cases when a third-party payer perspective is adopted. Catch-up programs provide additional savings.

Clade, Country and Region-specific HIV-1 Vaccines: Are they necessary?

Today, scientists are often encouraged to custom-design vaccines based on a particular country or clade. Here, we review the scientific literature and then suggest that the overwhelming endeavor to produce a unique vaccine for every world region or virus subtype may not be necessary.

Associations of daycare and school entry vaccination requirements with varicella immunization rates

School and daycare entry requirements have been credited with increasing immunization rates among school-age children, but no prior study has assessed the nationwide effects of entry requirements while controlling for individual, family, and household characteristics. The 2002 National Immunization Survey (NIS) is a nationally representative annual survey that includes provider record-verified immunization dates for 20,546 children aged 19-35 months without prior history of varicella. In weighted bivariate and multivariate logistic regression models, we examined the association of state entry mandate implementation with children's up-to-date (UTD) status for varicella vaccine, adjusted for sociodemographic characteristics of children, mothers, and household income and for children's UTD status for other recommended vaccines. In this national sample representative of 5.6 million children, 83.2% (95% CI: 82.3%-84.1%) were UTD for varicella vaccine. Between 1997 and 2002 inclusive, 33 states and the District of Columbia had implemented school and/or daycare entry immunization mandates for varicella. In bivariate analyses, 84.9% (83.9%-85.9%) of children in states with varicella entry mandates were UTD, compared to 76.8% (75.3%-78.4%) of children in states without such mandates. In multivariate analyses controlling for child and family characteristics, children living in states with varicella entry mandates remained significantly more likely to be UTD for varicella than children in states without mandates. These findings indicate that immunization entry requirements are associated with higher immunization rates among preschool-age children, and suggest that the effects of entry requirements are independent of other individual and household factors associated with childhood immunization.

Importance of catch-up vaccination: experience from a varicella outbreak, Maine, 2002-2003

OBJECTIVE

During December 2002 to January 2003, a varicella outbreak occurred in an elementary school in Maine. Just 1 month before detecting the outbreak, Maine implemented varicella vaccine requirements for child care but did not require vaccination for school entry. We investigated this outbreak to examine reasons for its occurrence, including vaccine failure.

METHODS

A self-administered questionnaire was sent to all students' parents to determine student disease status, medical conditions, and vaccination status, which was further confirmed by review of medical records. Parental reporting of chickenpox/varicella that occurred since September 1, 2002, in a student who attended the school was used to define a case. Parents of cases were interviewed by telephone about disease characteristics. Disease severity was classified on the basis of the number of skin lesions and the occurrence of complications. Vaccine effectiveness was calculated by comparing varicella attack rates for any disease, for moderate to severe disease, and for severe disease among vaccinated and unvaccinated students.

RESULTS

We obtained complete information for 296 (81%) of 364 students. Varicella vaccine coverage was 74% overall and decreased by grade, from 90% in kindergarten to 60% in third grade. Attack rates increased significantly from 14% in kindergarten to 37% in third grade. Of the 53 varicella cases, 36 (68%) were unvaccinated, 12 (22%) were vaccinated, and 5 (10%) had previous disease history. Vaccine effectiveness was 89% (95% confidence interval [CI]: 79-94%) against disease of any severity, 96% (95% CI: 88-99%) against moderate to severe disease, and 100% (95% CI: undefined) against severe disease. Twenty-two percent of unvaccinated students had severe disease and 1 was hospitalized for a skin infection, whereas none of the vaccinated cases reported severe disease.

CONCLUSION

This outbreak was attributable primarily to failure to vaccinate, especially among children in grades 1 through 3. Catch-up vaccination of susceptible older children and adolescents is especially important to prevent accumulation of susceptibility in these groups, in which the natural disease is more severe. School entry requirements will contribute to a more rapid implementation of the existing recommendations for vaccination.

Decline in mortality due to varicella after implementation of varicella vaccination in the United States

BACKGROUND

Varicella disease has been preventable in the United States since 1995. Starting in 1999, active and passive surveillance data showed sharp decreases in varicella disease. We reviewed national death records to assess the effect of the vaccination program on mortality associated with varicella.

METHODS

Data on deaths for which varicella was listed as an underlying or contributing cause were obtained from National Center for Health Statistics Multiple Cause-of-Death Mortality Data for 1990 through 2001. We calculated the numbers and rates of death due to varicella according to age, sex, race, ethnic background, and birthplace.

RESULTS

The rate of death due to varicella fluctuated from 1990 through 1998 and then declined sharply. For the interval from 1990 through 1994, the average number of varicella-related deaths was 145 per year (varicella was listed as the underlying cause in 105 deaths and as a contributing cause in 40); it then declined to 66 per year during 1999 through 2001. For deaths for which varicella was listed as the underlying cause, age-adjusted mortality rates dropped by 66 percent, from an average of 0.41 death per 1 million population during 1990 through 1994 to 0.14 during 1999 through 2001 (P<0.001). This decline was observed in all age groups under 50 years, with the greatest reduction (92 percent) among children 1 to 4 years of age. In addition, by the period from 1999 through 2001, the average rates of mortality due to varicella among all racial and ethnic groups were below 0.15 per 1 million population, as compared with rates ranging from 0.37 per 1 million for whites to 0.66 per 1 million for other races in the period from 1990 through 1994.

CONCLUSIONS

The program of universal childhood vaccination against varicella in the United States has resulted in a sharp decline in the rate of death due to varicella.

[Varicella vaccine]

A live virus attenuated vaccine was developed from the OKA strain (isolated from vesicles in the OKA child, 3 years of age, presenting with a benign varicella). The vaccine was completed after 11 propagation at 34 degrees C on HELF cells. The vaccine is a lyophilized preparation of a live attenuated virus, obtained by propagation of the virus in MRC-5 human diploid cell culture, titering between 1500 and 5000 cfu (colony forming unit per milliliter). This attenuated virus, contrary to the wild virus, is thermo-sensitive (39 degrees C). The rate of seroconversion after administration of one vaccine dose in healthy children, from 12 months to 12 years of age, ranges from 93% to 100% (Table 1). In controlled studies, the efficiency for the prevention of varicella in children reaches at least 85% with a 2-4 years follow-up. The prevention of severe forms is at least 95%.

The impact of varicella vaccination in the United States

The addition of varicella vaccine to the universal childhood immunization schedule in the United States in 1995 can be seen as a bold step. Shown to be safe and efficacious against varicella in extensive prelicensure studies, it is nonetheless the first vaccine against a herpesvirus and, furthermore, it is a live, attenuated vaccine. Both wild-type and vaccine strain varicella zoster virus (VZV) are noteworthy for their ability to establish latent infection within the host, with the subsequent possibility of reactivation. Therefore, at the population level, a successful vaccination program could result in the eventual displacement of wild-type VZV by the attenuated vaccine virus. The immediate objective of universal vaccination, however, was to reduce the significant morbidity and mortality associated with primary VZV infection. Data now accumulating suggest that the varicella vaccine as used in the United States has so far been highly effective. The challenge for the future is to predict how the resulting substantial reduction in circulation of VZV will affect immunity among both vaccinees and the unvaccinated. Vaccination strategies likely will need to be adjusted as the epidemiology of VZV in the United States continues to evolve.

Preventing varicella-zoster disease

Varicella-zoster virus (VZV), the cause of chickenpox and shingles, is a pathogen in retreat following the introduction of mass vaccination in the United States in 1995. The live attenuated Oka vaccine, which is safe and immunogenic, gives good protection against both varicella and zoster in the short to medium term. It has undoubtedly been highly effective to date in reducing all forms of varicella, especially severe disease. However, the huge pool of latent wild-type virus in the population represents a continuing threat. Both the biology and the epidemiology of VZV disease suggest that new vaccination strategies will be required over time.

Comparison of varicella history with presence of varicella antibody in refugees

OBJECTIVE

To compare history of varicella with presence of varicella antibody in refugees and to determine the number of unnecessary doses of varicella vaccine administered to refugee children > or =7 years of age.

METHODS

Cross-sectional study of refugees > or =7 years of age evaluated between July 2000 and October 2002 by the Refugee Health Assessment Program at Boston Medical Center. We recorded age, sex, region of origin, varicella history, and results of serologic testing for presence of varicella antibodies.

RESULTS

Eighty-eight percent of individuals with a positive history of clinical varicella had varicella antibody; 65% of those with negative history had varicella antibody. The positive predictive value of a history of clinical varicella was 88%. The negative predictive value of a negative history was 39%.

CONCLUSION

History of varicella was not a reliable predictor of presence or absence of varicella antibody in refugees. Strategies to protect individuals with negative histories of clinical varicella include immediate immunization or serotesting followed by immunization of susceptible individuals. Relying on positive histories of clinical varicella may leave some individuals susceptible to varicella and impede efforts to eliminate varicella in the US.

Chickenpox or Smallpox: The Use of the Febrile Prodrome as a Distinguishing Characteristic

BACKGROUND

The ability to differentiate chickenpox from smallpox is important for early recognition of bioterrorism events and prevention of false alarms. The febrile prodrome is a clinical feature used to differentiate these conditions. However, the prevalence of prodromal manifestations in chickenpox has not been well established.

METHODS

We evaluated prodrome characteristics of all chickenpox cases identified through an active varicella surveillance program over a 21-month period. The frequencies of various prodromal manifestations among vaccinated and unvaccinated case patients were assessed, and the impact of other demographic features on these manifestations was evaluated. Data were analyzed to determine what proportion met the smallpox febrile prodrome criteria as elaborated in the Centers for Disease Control and Prevention algorithm for evaluating patients suspected of having smallpox. Finally, we compared our data with historical data on smallpox prodromes.

RESULTS

Data on prodrome characteristics were available for 932 chickenpox cases. Prodromal fever was present in 37% of unvaccinated chickenpox case patients and in 25% of vaccinated case patients. Among unvaccinated case patients, adults were 70% more likely than children to have fever in the prodrome period. We found that prodromes are less common and less severe in chickenpox than in smallpox. Nevertheless, 7%-17% of unvaccinated chickenpox case patients meet the smallpox febrile prodrome criteria.

CONCLUSIONS

Febrile prodromes occur in a significant proportion of patients with chickenpox, particularly among unvaccinated case patients and adults. Therefore, the febrile prodrome alone is not a sufficient marker of smallpox risk. All major and minor smallpox criteria should be considered together in assessing the likelihood of smallpox.

High rate of varicella complications among Mexican-born adults in Alabama

OBJECTIVE

Our study examines risk factors for severe varicella in an outbreak among Mexican-born adults, and it compares susceptibility to infection and reliability of self-reported varicella history for these individuals with that for adults born in the United States in the outbreak locale, which may guide vaccination strategies.

METHODS

We interviewed case patients and non-case persons in the affected apartment complex and workplace, assessed disease history and susceptibility by testing for varicella-zoster virus immunoglobulin G antibodies, and reviewed the clinical data of case patients.

RESULTS

Five of 18 case patients had serious complications for which they sought medical care; 1 was hospitalized for pneumonia, and 1 was hospitalized for Guillain-Barré syndrome. Only intense exposure (e.g., sharing a bed) was marginally associated with severe disease (P=.08). In the workplace, varicella susceptibility was higher among Mexican-born workers (20%) than among workers born in the United States (3%) (adjusted prevalence odds ratio, 5.4; 95% confidence interval, 2.3-14.8). Mexican-born persons had the highest positive predictive value of self-reported disease (100%) in predicting immunity, and those born in the United States had the lowest negative predictive value of self-reported history (10%) in predicting susceptibility.

CONCLUSIONS

Varicella is a more serious disease among adults than among children, and Mexican-born adults living in the United States might have a higher risk of acquiring varicella than US-born adults. Varicella outbreaks involving adults should be prioritized for control efforts. Outbreaks can be prevented by vaccinating susceptible adults.

Effects of varicella vaccination on herpes zoster incidence

The effects of a general varicella vaccination programme on the incidence of herpes zoster are of major public health importance. This review focuses on two key aspects, namely the relationship between wild-type virus spread and the incidence of herpes zoster, as obtained from recent surveys, surveillance and observational studies, and the results from mathematical population models. Although knowledge is limited, close contact with varicella cases seems to have a protective effect. Thus, an increase in zoster incidence after varicella immunisation is possible, but the extent is unknown because of the influence of other factors independent of immunisation. Currently, vaccination effects estimated from mathematical modelling depend strongly on pre-specified assumptions. In order to obtain more precise predictions, the results of ongoing monitoring and clinical studies are awaited and further studies are suggested. Vaccination recommendations can be adapted at any time to take account of further findings in this area.

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 diseases, compared with annual shingles consultation rates from the same scheme to exclude reporting fatigue and data from a general practice morbidity database to validate results.

SETTING

A total of 226,884 patients registered with one of 30 volunteer general practices participating in the sentinel surveillance scheme.

MAIN OUTCOME MEASURES

Age standardised and age specific incidence of chickenpox.

RESULTS

Crude and age standardised consultation rates for chickenpox declined from 1986 to 2001, with loss of epidemic cycling. Rates remained stable in 0-4 year olds but declined in all older age groups, particularly those aged 5-14 years. Shingles consultation rates remained constant over the same period. Data from the morbidity database displayed similar trends.

CONCLUSION

General practitioner consultation rates for chickenpox are declining in Wales except in pre-school children. These findings are unlikely to be a reporting artefact but may be explained either by an overall decline in transmission or increased social mixing in those under 5 years old, through formal child care and earlier school entry, and associated increasing rates of mild or subclinical infection in this age group. Further investigation, particularly by serological surveillance, is necessary before universal varicella immunisation can be considered in the UK.

Decline in varicella-related hospitalizations and expenditures for children and adults after introduction of varicella vaccine in the United States

OBJECTIVE

Universal childhood immunization against varicella in the United States, first recommended in 1995, was predicted to lead to significant decreases in varicella-related hospitalization rates and corresponding charges. Previous studies have not found such effects. We studied trends in varicella-related hospitalization rates and associated charges before and after introduction of varicella vaccine.

METHODS

We examined hospitalization and charge data from the Nationwide Inpatient Sample for the years 1993-2001, representative of national hospitalization patterns for children and adults. We derived weighted estimates of population-adjusted, varicella-related hospitalization rates and inflation-adjusted, varicella-related hospital charges.

RESULTS

The annual varicella-related hospitalization rate exceeded 0.5 hospitalizations per 10,000 US population from 1993 to 1995, declined to 0.26 per 10,000 by 1999, and again halved to 0.13 per 10,000 by 2001. Hospitalization rates declined most substantially among individuals primarily targeted for vaccination (0- to 4-year-old children) but decreased among youths aged 5 to 19 years and among adults as well. Concomitantly, varicella-related hospital charges declined from 161.1 million dollars (95% confidence interval: 130.5 million dollars-191.8 million dollars) in 1993 to 66.3 million dollars (95% confidence interval: 50.9 million dollars-81.7 million dollars) in 2001 (all 2001 US dollars). Among expected primary payers, inflation-adjusted declines in varicella-related hospital discharges-related charges accrued to Medicaid, private insurance, and "other" payers (including uninsured and self-pay) but not to Medicare.

CONCLUSIONS

This national analysis indicates a clinically and statistically significant reduction in varicella-related hospitalizations for children and adults associated with childhood varicella immunization in the United States and a corresponding significant decrease in hospital charges.

A review of the varicella vaccine in immunocompromised individuals

BACKGROUND

Individuals with underlying cell-mediated immunodeficiency disorders are at high risk of developing severe, life-threatening illness associated with varicella-zoster virus infection. A live-attenuated varicella vaccine is recommended for routine childhood immunisation in some countries. In healthy children, the vaccine is efficacious and safe but because immunocompromised individuals may be unable to limit replication of live-attenuated vaccine viruses, the varicella vaccine is not recommended for them and there are few exceptions.

OBJECTIVES

The purpose of this paper is to review the published studies addressing the use of the varicella vaccine in people with cell-mediated immunodeficiency disorders.

METHODS

A computerised search on the PubMed database was used to collect the relevant papers published up to March 2003.

RESULTS

The varicella vaccine has been extensively studied in susceptible children with acute lymphoblastic leukaemia in remission, but studies involving individuals with other immunodeficiency disorders are scarce. Some of the current recommendations are based on very few and small studies with short follow-up. Immunocompromised individuals should be given the varicella vaccine only with complete knowledge of their clinical and immunological conditions and after considering the risks of natural infection and vaccination.

An economic evaluation of varicella vaccination in Italian adolescents

An economic evaluation was performed to assess five varicella vaccination scenarios targeted to 11-year-old Italian adolescents. The scenarios were: "compulsory vaccination" of all adolescents, recommended vaccination of susceptible adolescents on the basis of an "anamnestic screening", a "blood test" or a combination of both ("both tests") and vaccination of adolescents in the private sector, at the parents' charge ("private vaccination"). Probabilities and unit costs were taken from published sources and experts opinion. The accuracy of the anamnestic screening (81.6% sensitivity and 87.3% specificity) was derived from a separate descriptive study among 344 Italian adolescents. The costs and benefits of each scenario were simulated using a Markov model and cost-effectiveness, budget-impact and cost-benefit analyses were conducted. Of all considered scenarios, "both tests" and "anamnestic screening" were the most appealing options with an estimated net direct cost of 5058 and 8929 per life-year gained (compared to no vaccination) versus 14,693-42,842 for the other scenarios. These two scenarios further resulted in substantial net savings for society (over 600,000 per cohort, BCR: 2.17). The need for a serological confirmation was highly dependent on the sensitivity of the anamnestic screening, which is believed to increase once such a program is launched. For practical considerations, "anamnestic screening" seems to be the most convenient option.

Live viral vaccines in the control of highly infectious diseases: measles and varicella

It is possible that by the end of this decade, measles and varicella two of the most infections and previously universal diseases of children, with massive levels of morbidity and significant mortality, may become of historical interest only. To accomplish this success, it is imperative that all involved parties do what is required. The vaccine supply must be assured, parents must be appropriately educated and reinforced by the media to bring their children to be immunized, and healthcare personnel must both aggressively ascertain and administer needed immunizations.

Immunizations, neonatal jaundice, and animal-induced injuries

PURPOSE OF REVIEW

Published studies during the past year about three topics important to the pediatric clinician-- immunizations, neonatal jaundice, and animal-induced injuries-are concisely reviewed.

RECENT FINDINGS

Recent updates regarding vaccines including the questionable link with autism, implementation of universal influenza vaccination for young children, the efficacy of pneumococcal vaccine against invasive disease, and new information on pertussis, varicella, hepatitis A, hepatitis B, measles, and rotavirus vaccination are discussed. No association between measles/mumps/rubella vaccine or thimerosal-containing pertussis vaccine and autism is evident. Universal influenza vaccination for children 6 to 23 months of age will be recommended for the 2004-2005 flu season, and this implementation should reduce significant school absenteeism as well as complications seen last year including encephalopathy, seizures, respiratory failure, and pneumonia. Pneumococcal vaccine significantly reduces rates of invasive pneumococcal vaccine in healthy and HIV-infected children, although it does not appear to greatly affect otitis media rates. A reduction in post-vaccine febrile seizures appears to be present since the introduction of acellular pertussis vaccine. Multiple outbreaks in varicella have been reported since the introduction of the varicella vaccine, and a booster vaccination may be necessary in the future. Methods for detecting and preventing severe neonatal hyperbilirubinemia are reviewed, as well as anticipated recommendations from the American Academy of Pediatrics for the detection and management of hyperbilirubinemia. High bilirubin levels in preterm infants may result in hearing dysfunction and developmental impairment. The American Academy of Pediatrics has recommended a higher level of monitoring for newborn jaundice and treatment of hyperbilirubinemia in an effort to prevent kernicterus and sequelae from elevated bilirubin levels, including post-discharge follow-up appointment by day 3 to 5 of age. Dog bites in children with resultant post-traumatic stress disorder, rabies, and salmonellosis from pet reptiles in the home are also addressed. Clinicians need to be aware of the risk for rabies bites, need to recognize that dog bites in children appear to cause post-traumatic stress disorder in more than half of cases, and need to know how to educate patients on how to prevent salmonellosis from pet reptiles and amphibians.

SUMMARY

Progress has been made in immunizations, especially immunization for influenza, pneumonia, and pertussis. It is recommended that monitoring for neonatal hyperbilirubinemia be more thorough to prevent the consequences of this condition. Rabies, post-traumatic stress disorder from dog bites, and salmonellosis associated with pet reptiles constitute an important area for patient education.