The risk of zoster after varicella vaccination in children with leukemia

Serious neurological adverse events in immunocompetent children and adolescents caused by viral reactivation in the years following varicella vaccination

Serious adverse events following vaccination include medical complications that require hospitalisation. The live varicella vaccine that was approved by the Food and Drug Administration in the United States in 1995 has an excellent safety record. Since the vaccine is a live virus, adverse events are more common in immunocompromised children who are vaccinated inadvertently. This review includes only serious adverse events in children considered to be immunocompetent. The serious adverse event called varicella vaccine meningitis was first reported in a hospitalised immunocompetent child in 2008. When we carried out a literature search, we found 15 cases of immunocompetent children and adolescents with varicella vaccine meningitis; the median age was 11 years. Eight of the children had received two varicella vaccinations. Most of the children also had a concomitant herpes zoster rash, although three did not. The children lived in the United States, Greece, Germany, Switzerland, and Japan. During our literature search, we found five additional cases of serious neurological events in immunocompetent children; these included 4 cases of progressive herpes zoster and one case of acute retinitis. Pulses of enteral corticosteroids as well as a lack of herpes simplex virus antibody may be risk factors for reactivation in immunocompetent children. All 20 children with adverse events were treated with acyclovir and recovered; 19 were hospitalised and one child was managed as an outpatient. Even though the number of neurological adverse events remains exceedingly low following varicella vaccination, we recommend documentation of those caused by the vaccine virus.

Varicella Vaccine Meningitis as a Complication of Herpes Zoster in Twice-Immunized Immunocompetent Adolescents

Varicella-zoster virus vaccination is recommended for virtually all young children in the United States, Canada, and several other countries. Varicella vaccine is a live attenuated virus that retains some of its neurotropic properties. Herpes zoster caused by vaccine virus still occurs in immunized children, although the rate is much lower than in children who had wild-type varicella. It was commonly thought that 2 varicella vaccinations would protect children against the most serious complication of meningitis following herpes zoster; however, 2 meningitis cases have already been published. We now report a third case of varicella vaccine meningitis and define risk factors shared by all 3 immunized adolescents. The diagnosis in cerebrospinal fluid in this third case was verified by amplifying and sequencing portions of the viral genome, to document fixed alleles found only in the vaccine strain. Viral antibody was also detected in the cerebrospinal fluid by confocal microscopy. When compared with the other 2 cases, remarkably all 3 were 14 years old when meningitis occurred. All 3 were treated with intravenous acyclovir, with complete recovery. The adolescent in our case report also had recurrent asthma, which was treated with both prednisone tablets and beclomethasone inhaler before onset of meningitis. When the 3 cases were considered together, they suggested that immunity to varicella-zoster virus may be waning sufficiently in some twice-immunized adolescents to make them vulnerable to varicella vaccine virus reactivation and subsequent meningitis. This complication rarely happens in children after wild-type varicella.

Sleep in Parkinson's disease

Sleep disturbances are common in Parkinson's disease and comprise the entire spectrum of sleep disorders. On the one hand regulation of sleep and wakefulness is affected in Parkinson's disease, leading to the development of disorders, such as insomnia and daytime sleepiness. While on the other hand control of motor activity during sleep is impaired, with subsequent manifestation of parasomnias (mainly REM sleep behavior disorders, but also, albeit more rarely, sleepwalking, and overlap parasomnia). Restless legs syndrome has been reported to be frequent in patients with Parkinson's disease, although there is no consensus on whether it is more frequent in Parkinson's disease than in the general population. The same is true for sleep-related breathing disorders. Regarding the diagnosis of sleep disorders in patients with Parkinson's disease, one of the main challenges is correctly identifying excessive daytime sleepiness as there are many potential confounding factors, for example it is necessary to distinguish sleep-related breathing disorders from medication effects, and to distinguish restless legs syndrome from the concomitant presence of potential mimics specific to Parkinson's disease, such as akathisia, nocturnal leg cramps, nocturnal hypokinesia, early morning dystonia, etc. The correct diagnosis of REM sleep behavior disorder is also not always easy, and video-polysomnography should be performed in order to exclude mimic-like movements at the end of sleep apneas or violent periodic leg movements of sleep. These aspects and specific considerations about diagnosis and treatment of sleep disorders in patients with Parkinson's disease will be reviewed.

Vaccines for post-exposure prophylaxis against varicella (chickenpox) in children and adults

BACKGROUND

The prevention of varicella (chickenpox) using live attenuated varicella vaccines has been demonstrated both in randomised controlled trials (RCTs) and in population-based immunisation programmes in countries such as the United States and Australia. Many countries do not routinely immunise children against varicella and exposures continue to occur. Although the disease is often mild, complications such as secondary bacterial infection, pneumonitis and encephalitis occur in about 1% of cases, usually leading to hospitalisation. The use of varicella vaccine in persons who have recently been exposed to the varicella zoster virus has been studied as a form of post-exposure prophylaxis (PEP).

OBJECTIVES

To assess the efficacy and safety of vaccines for use as PEP for the prevention of varicella in children and adults.

SEARCH METHODS

We searched CENTRAL (2014, Issue 1), MEDLINE (1966 to March week 1, 2014), EMBASE (January 1990 to March 2014) and LILACS (1982 to March 2014). We searched for unpublished trials registered on the clinicaltrials.gov and WHO ICTRP websites.

SELECTION CRITERIA

RCTs and quasi-RCTs of varicella vaccine for PEP compared with placebo or no intervention. The outcome measures were efficacy in prevention of clinical cases and/or laboratory-confirmed clinical cases and adverse events following vaccination.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted and analysed data using Review Manager software.

MAIN RESULTS

We identified three trials involving 110 healthy children who were siblings of household contacts. The included trials varied in study quality, vaccine used, length of follow-up and outcomes measured and, as such, were not suitable for meta-analysis. We identified high or unclear risk of bias in two of the three included studies. Overall, 13 out of 56 vaccine recipients (23%) developed varicella compared with 42 out of 54 placebo (or no vaccine) recipients (78%). Of the vaccine recipients who developed varicella, the majority only had mild disease (with fewer than 50 skin lesions). In the three trials, most participants received PEP within three days following exposure; too few participants were vaccinated four to five days post-exposure to ascertain the efficacy of vaccine given more than three days after exposure. No included trial reported on adverse events following immunisation.

AUTHORS' CONCLUSIONS

These small trials suggest varicella vaccine administered within three days to children following household contact with a varicella case reduces infection rates and severity of cases. We identified no RCTs for adolescents or adults. Safety was not adequately addressed.

Advances in the management of viral infections

Viral infections are common in cancer patients. The risk and severity of infection are influenced by patient, disease, treatment, and viral factors. Severe viral infections are more likely to occur in treatment regimens that are more immunosuppressive. Historically, the most frequent severe infections have been due to herpesviruses, but more recently, other pathogens, especially community respiratory and hepatitis viruses, have received increasing attention as major viral pathogens in cancer patients. Because of the new diagnostic assays and the introduction of better therapeutic options, knowledge of viral infections is important in optimizing antineoplastic therapies.

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

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

Safety and immunogenicity of the live attenuated varicella vaccine following T replete or T cell-depleted related and unrelated allogeneic hematopoietic cell transplantation (alloHCT)

There are limited studies assessing the live attenuated varicella vaccine following allogeneic hematopoietic cell transplantation (alloHCT). Because of the morbidity of varicella acquired after childhood, we immunized and retrospectively analyzed the safety and immunogenicity of this vaccine in 46 varicella zoster virus (VZV) seronegative patients <20 years old at HCT who achieved a CD4 cell count ≥200/μL, were off immunosuppression, and responded to ≥1 post-HCT vaccines. Two vaccinated patients lacking follow-up titers were excluded from analysis. Stem cells were derived from an HLA-matched sibling (n = 18) or an alternative (HLA mismatched related or unrelated) donor (n = 26). Median time to vaccination was 4 years. Sixty-four percent of patients seroconverted following 1 immunization. There was no significant difference in response between recipients of a matched related or alternative donor graft (P = .2) or between those given a T cell-depleted or T-replete alternative donor graft (P = .27). Three of 44 patients developed a self-limited varicella-like rash within 2.5 weeks of immunization. With a median follow-up of 29.1 (range: 6.9-167.1) months, there were no subsequent cases of varicella-like rashes. No patient developed shingles. This study suggests that this vaccine is safe and immunogenic when given according to preset clinical and immunologic milestones, warranting larger prospective studies in patients ≥24 months following HCT as outlined in current post-HCT vaccine guidelines.

Molecular studies of the Oka varicella vaccine

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

Impact of varicella vaccine on varicella-zoster virus dynamics

The licensure and recommendation of varicella vaccine in the mid-1990s in the United States have led to dramatic declines in varicella incidence and varicella-related deaths and hospitalizations. Varicella outbreaks remain common and occur increasingly in highly vaccinated populations. Breakthrough varicella in vaccinated individuals is characteristically mild, typically with fewer lesions that frequently do not progress to a vesicular stage. As such, the laboratory diagnosis of varicella has grown increasingly important, particularly in outbreak settings. In this review the impact of varicella vaccine on varicella-zoster virus (VZV) disease, arising complications in the effective diagnosis and monitoring of VZV transmission, and the relative strengths and limitations of currently available laboratory diagnostic techniques are all addressed. Since disease symptoms often resolve in outbreak settings before suitable test specimens can be obtained, the need to develop new diagnostic approaches that rely on alternative patient samples is also discussed.

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.

Vaccines for post-exposure prophylaxis against varicella (chickenpox) in children and adults

BACKGROUND

Live attenuated varicella vaccines for the prevention of varicella (chickenpox) has been demonstrated both in randomised controlled trials (RCTs) and in population-based immunisation programmes in countries such as the United States. However, many countries do not routinely immunise children against varicella, and exposures continue to occur. Although the disease is often mild, complications such as secondary bacterial infection, pneumonitis and encephalitis occur in about 1% of cases, usually leading to hospitalisation. The use of varicella vaccine in persons who have recently been exposed to the varicella zoster virus has been studied as a form of post-exposure prophylaxis (PEP).

OBJECTIVES

To assess the efficacy and safety of vaccines for use as PEP for the prevention of varicella in children and adults.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2008, Issue 1); MEDLINE (1966 to February 2008); and EMBASE (January 1990 to February 2008).

SELECTION CRITERIA

RCTs and quasi-RCTs of varicella vaccine for PEP compared with placebo or no intervention. The outcome measures were efficacy in prevention of clinical cases and/or laboratory-confirmed clinical cases and adverse effects following vaccination.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted and analysed data using Review Manager software.

MAIN RESULTS

Three studies involving 110 healthy children who were siblings of household contacts were identified as suitable for inclusion. The studies varied in quality, study design, vaccine used, and outcomes measured and, as such, were not suitable for meta-analysis. Overall, 13 out of 56 vaccine recipients (18%) developed varicella compared with 42 out of 54 placebo (or no vaccine) recipients (78%). Of the vaccine recipients who developed varicella, the majority only had mild disease (with less than 50 skin lesions). In the three studies, most subjects received PEP within three days following exposure; too few subjects were vaccinated four to five days post exposure to ascertain the efficacy of vaccine given more than three days after exposure. No included studies reported on adverse events following immunisation.

AUTHORS' CONCLUSIONS

These small trials suggest varicella vaccine administered within three days to children following household contact with a varicella case reduces infection rates and severity of cases. No RCTs for adolescents or adults were identified. However safety was not adequately addressed.

Discriminating between varicella-zoster virus vaccine and wild-type strains by loop-mediated isothermal amplification

The loop-mediated isothermal amplification (LAMP) method was developed to distinguish between the varicella-zoster virus (VZV) vaccine (vOka) strain and wild-type strains. Two single nucleotide polymorphisms (SNPs) (nucleotide [nt] 105705 for VR-1 VZV LAMP and nt 106262 for VR-2 VZV LAMP) located in the open reading frame 62 gene were selected as LAMP targets. Amplified vOka DNA demonstrated a typical ladder pattern; however, no LAMP product was detected in reactions performed with DNAs from other human herpesviruses by either VR-1 VZV LAMP or VR-2 VZV LAMP. This result was confirmed by a turbidity assay. The sensitivities of both VR-1 and VR-2 VZV LAMP determined by either the turbidity assay or agarose gel electrophoresis were 100 copies per reaction. To discriminate the vOka strain from wild-type strains, VR-1 and VR-2 VZV LAMP products were digested with the appropriate restriction enzymes (SacII for VR-1 LAMP and SmaI for VR-2 LAMP). The digested products were clearly different in the vOka strain and wild-type strains. To evaluate the utility of the LAMP methods for rapid differentiation, viral DNA (without DNA extraction) in swab samples was directly tested. Wild-type VZV DNA was detected in 20 swab samples by either VR-1 VZV LAMP or VR-2 VZV LAMP. Sequence analysis confirmed the expected SNPs in the LAMP products amplified from the vOka strain and the five wild-type strains.

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.

Aberrant infection and persistence of varicella-zoster virus in human dorsal root ganglia in vivo in the absence of glycoprotein I

Varicella-zoster virus (VZV) causes varicella, establishes latency in sensory ganglia, and reactivates as herpes zoster. Human dorsal root ganglia (DRGs) xenografts in immunodeficient mice provide a model for evaluating VZV neuropathogenesis. Our investigation of the role of glycoprotein I (gI), which is dispensable in vitro, examines the functions of a VZV gene product during infection of human neural cells in vivo. Whereas intact recombinant Oka (rOka) initiated a short replicative phase followed by persistence in DRGs, the gI deletion mutant, rOkaDeltagI, showed prolonged replication with no transition to persistence up to 70 days after infection. Only a few varicella-zoster nucleocapsids and cytoplasmic virions were observed in neurons, and the major VZV glycoprotein, gE, was retained in the rough endoplasmic reticulum in the absence of gI. VZV neurotropism was not disrupted when DRG xenografts were infected with rOka mutants lacking gI promoter elements that bind cellular transactivators, specificity factor 1 (Sp1) and upstream stimulatory factor (USF). Because gI is essential and Sp1 and USF contribute to VZV pathogenesis in skin and T cells in vivo, these DRG experiments indicate that the genetic requirements for VZV infection are less stringent in neural cells in vivo. The observations demonstrate that gI is important for VZV neurotropism and suggest that a strategy to reduce neurovirulence by deleting gI could prolong active infection in human DRGs.

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.

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.

Consensus: varicella vaccination of healthy children--a challenge for Europe

The seriousness of varicella-zoster virus (VZV) infection as a public health issue is becoming clearer as country-specific epidemiologic and pharmacoeconomic data become available. In Germany, for example, studies have shown that >5.5% of immunologically healthy individuals develop varicella-related complications such as bacterial superinfections, acute neurologic disorders, pneumonia, bronchitis and otitis media; whereas in Italy, 3.5 to 5% of childhood cases of varicella cause complications such as upper respiratory tract and cutaneous infections. Varicella vaccines are now available. These live attenuated Oka strain vaccines have been shown in extensive studies to be highly immunogenic and well-tolerated in immunocompetent and immunocompromised children, with seroconversion rates ranging from 94 to 100% and 53 to 100%, respectively. These vaccines are also highly effective against clinical disease. These considerations led to a reevaluation of varicella vaccination policies. A routine varicella vaccination program targeting healthy children has already been implemented in the US, and data produced are encouraging and valuable. Similar strategies have not yet been adopted across Europe. The European Working Group on Varicella (EuroVar) was formed in 1998 to address the issues surrounding varicella epidemiology in Europe. After a series of meetings, the EuroVar members prepared a consensus statement recommending routine varicella vaccination for all healthy children between 12 and 18 months and to all susceptible children before their 13th birthday, in addition to catch-up vaccination in older children and adults who have no reliable history of varicella and who are at high risk of transmission and exposure. However, such a policy is recommended only if a very high coverage rate can be achieved. This could be reached with a measles-mumps-rubella-varicella combined vaccine.

Cost-benefit analysis of routine childhood vaccination against chickenpox in Taiwan: decision from different perspectives

Cost-benefit analysis was conducted to determine whether it is worthwhile to initiate a routine varicella vaccination program in Taiwan from different perspectives. Using the human capital approach, the discounted net cost for vaccination program was New Taiwan Dollars (NTD) 281 million from health care payer's perspective. Taking indirect costs into account, the net saving due to vaccination program was NTD 425 million from the societal perspective. In terms of benefit-cost ratio, a mass varicella vaccination program could only save NTD 0.34 in discounted costs for each dollar incurred in a vaccination program from health care payer's perspective whereas save NTD 2.06 from the societal viewpoint. Results based on the willingness-to-pay (WTP) method showed the Net Present Value (NPV) of the vaccination program was estimated as -NTD 272 million. We conclude that a routine varicella vaccination program is worthwhile from the societal perspective but neither from health care payer's nor from consumer decision based on the perspective of WTP.

Do the benefits of varicella vaccination outweigh the long-term risks? A decision-analytic model for policymakers and pediatricians

Although varicella vaccine is recommended for infants, many physicians and parents have withheld vaccination from infants because of concerns about the vaccine's long-term efficacy. We used a decision-analytic Markov model to examine the effects of decreasing vaccine efficacy on individuals and society. The model incorporated published data on age-specific incidence, morbidity, and mortality rates, as well as data on shifting disease burden from childhood to adulthood as vaccine compliance increases. The effects of 2 vaccination strategies---vaccinating infants at age 12 months and waiting to vaccinate until children are 10 years of age---were compared with the effects of no vaccination. If the efficacy of the vaccine were to decrease by 75%, then 50% compliance with vaccination at age 12 months would save 1800 life-years and 12,800 quality-adjusted life-years annually in the United States. The quality-adjusted life expectancy of individuals vaccinated at age 12 months would be 63 h longer than that of nonvaccinated individuals and would increase to 79 h as vaccination compliance increases and the burden of chickenpox shifts to adulthood. Varicella vaccination of infants at age 12 months appears to be beneficial, even if the efficacy of the vaccine declines substantially.

Herpes zoster infection and postherpetic neuralgia

Varicella-zoster virus (VZV), the cause of chicken pox, establishes latent infection in sensory ganglia. Reactivation results in zoster (shingles), sometimes complicated by encephalitis (myelitis). Postherpetic neuralgia (PHN) is the major morbidity of zoster. PHN typically increases in frequency with age. The VZV vaccine, which was developed for children, may be effective in enhancing VZV immune reactivity and decreasing zoster in adults. Early antiviral treatment may be effective in decreasing PHN onset. Several other medications may be useful in treating established PHN. A recent report discussed intrathecal steroid use.

Biologic and geographic differences between vaccine and clinical varicella-zoster virus isolates

Vaccine and wild-type strains of varicella-zoster virus differ both in their biologic characteristics and in the clinical manifestations of infection caused by each strain. The biologic differences described for the vaccine strain (temperature sensitivity and host cell preference) probably reflect the methods used to adapt the wild-type strain to the in vitro growth conditions imposed during the attenuation process in cell culture. In addition, restriction fragment polymorphisms have been described that reflect geographic strain variations between the parental virus used to develop the vaccine strain and other wild-type strains. These polymorphisms have been exploited as tools for the identification and differentiation of vaccine and wild-type strains in clinical studies. Infection with the wild-type strain results in the typical extensive rash of varicella, frequent transmission to other susceptible contacts, establishment of latency, and in some individuals, reactivation with the clinical picture of zoster. Infection with the vaccine strain results in the development of a protective immune response, minimal rash in a minority of individuals, rare transmission to other susceptible contacts, and a greatly reduced risk of zoster.

Live-attenuated varicella vaccine

This article reviews the history and development of live attenuated varicella vaccine from its early days in Japan to its widespread use throughout the world. The vaccine has proven extremely safe after immunization of as many as 10 million healthy children and adults in the United States alone. The vaccine is also highly immunogenic and offers close to 100% protection from severe chickenpox and 90% protection from illness. It is expected to have a major impact on the epidemiology of varicella and zoster in countries with high vaccine uptake.

Rapid genotyping of varicella-zoster virus vaccine and wild-type strains with fluorophore-labeled hybridization probes

We developed a single-tube rapid method for the detection and differentiation of varicella-zoster virus (VZV) vaccine and wild-type strains that combines rapid-cycle PCR with wild-type-specific fluorescent probe melting profiles for product genotyping. A region including the polymorphic site in VZV open reading frame (ORF) 62 was amplified in the presence of two fluorescence-labeled hybridization probes. During the annealing step of the thermal cycling, both probes bound to their complementary sequences in the amplicon, resulting in resonance energy transfer, thus providing real-time fluorescence monitoring of PCR. Continuous acquisition of fluorescence data during a melting curve analysis at the completion of PCR revealed that loss of fluorescence occurred in a strain-specific manner as the detection probe, which was fully complementary to the wild-type VZV ORF 62 region, melted off the template. Use of this method allowed genotyping of samples within minutes after the completion of PCR, eliminating the need for post-PCR sample manipulation. In addition to reducing the time required to produce a result, this method substantially reduces the risk of contamination of the final product as well as the risk of sample tracking errors. The genotypes of 79 VZV-positive samples determined by this fluorescent resonance energy transfer (FRET) method were identical to the genotypes obtained by conventional PCR and restriction fragment length polymorphism analysis. The genotyping of VZV strains by the FRET method is a rapid and reliable method that is suitable for typing and that is also practical for use for the processing of large numbers of specimens.

Varicella vaccine

Varicella vaccine is safe, effective, and cost-effective in healthy children, adolescents, and adults. Breakthrough cases of MVLS are significantly milder than wild-type varicella infection. No severe adverse events have been reported following vaccination, and the incidence of herpes zoster is less in vaccinees than in individuals who have had natural varicella infections. To date, there is no evidence waning immunity following vaccination. "New and improved" varicella vaccines that may be more effective than the current vaccine and can be stored at refrigerator temperatures may soon become available in the United States.

Incidence, risk factors and outcome of varicella-zoster virus infection in children after haematopoietic stem cell transplantation

We report a retrospective analysis of VZV infection after haematopoietic stem cell transplantation (HSCT) in children. Thirty-three (30%) of the total 109 children who were transplanted during a 7 year period developed post-transplant VZV infection. Twenty-four of these 33 (73%) children had VZV infection within 1 year following HSCT. The cumulative incidences of post-transplant VZV infection at 1 and 5 years were 26% and 45%, respectively. The positive and negative predictive values of pretransplant VZV serology in recipients on the development of HZ following HSCT were 39% and 88%, respectively. Pretransplant VZV seropositivity in recipients was the only risk factor for post-transplant herpes zoster (HZ) infection on multivariate analysis. All patients responded to acyclovir. The median duration of VZV infection was 5 days. Three (11%) and one (3%) children with HZ developed visceral dissemination and post-herpetic neuralgia, respectively. No mortality was directly attributed to VZV infection. VZV infection remains a major cause of morbidity in children after HSCT. Further studies are warranted to evaluate the potential use of VZV vaccine in these children. Bone Marrow Transplantation (2000) 25, 167-172.

Disturbance in bone turnover in children with a malignancy at completion of chemotherapy

BACKGROUND

Osteoporosis and pathological fractures have been observed in children with a malignancy. The mechanisms of osteopenia in childhood malignancies have not been well established. The purpose of the present study was to evaluate changes in bone turnover and in bone hormonal metabolism in children with a malignancy at completion of their chemotherapy.

PROCEDURE

Serum levels of human intact osteocalcin, type I collagen carboxyterminal propeptide (PICP), type I collagen carboxyterminal telopeptide (ICTP), 25-hydroxyvitamin D [25-(OH)-D], 1,25-dihydroxyvitamin D [1, 25-(OH)(2)-D], intact parathyroid hormone, insulin-like growth factor I (IGF-I), IGF binding protein 3 (IGFBP-3), alkaline phosphatase, calcium, and phosphate were analyzed in 22 children with acute lymphoblastic leukemia and in 26 children with other malignancies. Results were expressed as Z-scores [mean (95% confidence intervals)] relative to healthy Caucasian-children.

RESULTS

The marker of collagen degradation (ICTP) was significantly increased [1.43 (1.10-1.76), P < 0.0001] compared to reference values, whereas the markers of bone formation (PICP, osteocalcin) were not changed [0.07 (-0.55 to 0.49), 0.35 (-0.05 to 0.74), respectively, NS]. Serum 25-(OH)-D, 1,25-(OH)(2)-D, and calcium were significantly reduced [-0.65 (-0.87 to -0.42), -0.68 (-0.92 to -0. 42), -1.42 (-1.80 to -1.04), P < 0.0001, respectively].

CONCLUSIONS

Disturbance in bone turnover with low serum 25-(OH)-D, 1, 25-(OH)(2)-D, and calcium was observed in children with a malignancy at completion of their chemotherapy. A controlled study determining the possible benefits of vitamin D and calcium supplementation on bone turnover could be considered in these patients.

Herpesvirus vaccines. Development, controversies, and applications

Herpesviruses present difficult challenges in vaccine development because of their ability to evade immune clearance. Data and recommendations regarding the live-attenuated varicella vaccine are discussed. Approaches to developing vaccines to prevent herpes simplex virus (HSV), cytomegalovirus (CMV), and Epstein-Barr virus (EBV)-associated illnesses also are considered.

Current pharmacological approaches to the therapy of varicella zoster virus infections: a guide to treatment

Varicella zoster virus (VZV), a member of the herpesvirus family, is responsible for both primary (varicella, chickenpox) as well as reactivation (zoster, shingles) infections. In immunocompetent patients, the course of varicella is generally benign. For varicella zoster, post-herpetic neuralgia is the most common complication. In immunocompromised patients (particularly those with AIDS), transplant recipients and cancer patients, VZV infections can be life-threatening. For these patients and also for immunocompetent patients at risk such as pregnant women or premature infants, the current treatment of choice is based on either intravenous or oral aciclovir (acyclovir). The low oral bioavailability of aciclovir, as well as the emergence of drug-resistant virus strains, have stimulated efforts towards the development of new compounds for the treatment of individuals with VZV infections. Among these new compounds, penciclovir, its oral prodrug form famciclovir and the oral pro-drug form of aciclovir (valaciclovir), rank among the most promising. As with aciclovir itself, all of these drugs are dependent on the virus-encoded thymidine kinase (TK) for their intracellular activation (phosphorylation), and, upon conversion to their triphosphate form, they act as inhibitors/alternative substrate of the viral DNA polymerase. Therefore, cross-resistance to these drugs may be expected for those virus mutants that are TK-deficient and thus resistant to aciclovir. Other classes of nucleoside analogues dependent for their phosphorylation on the viral TK that have been pursued for the treatment of VZV infections include sorivudine, brivudine, fialuridine, fiacitabine and netivudine. Among oxetanocins, which are partially dependent on viral TK, lobucavir is now under clinical evaluation. Foscarnet, which does not require any previous metabolism to interact with the viral DNA polymerase, is used in the clinic when TK-deficient VZV mutants emerge during aciclovir treatment. TK-deficient mutants are also sensitive to the acyclic nucleoside phosphonates (i.e. [s]-1-[3-hydroxy-2-phosphonylmethoxypropyl]cytosine; HPMPC); these agents do not depend on the virus-encoded TK for their phosphorylation but depend on cellular enzymes for conversion to their diphosphoryl derivatives which then inhibit viral DNA synthesis. Vaccination for VZV has now come of age. It is recommended for healthy children, patients with leukaemia, and patients receiving immunosuppressive therapy or those with chronic diseases. The protection induced by the vaccine seems, to some extent, to include zoster and associated neuralgia. Passive immuniatin based on specific immunoglobulins does not effectively prevent VZV infection and is therefore restricted to high risk individuals (i.e. immunocompromised children and pregnant women).

Live attenuated varicella vaccine

Varicella-zoster virus (VZV) is a ubiquitous human pathogen that causes varicella, commonly called chicken pox; establishes latency; and reactivates as herpes zoster, referred to as shingles. A live attenuated varicella vaccine, derived from the Oka strain of VZV has clinical efficacy for the prevention of varicella. The vaccine induces persistent immunity to VZV in healthy children and adults. Immunization against VZV also has the potential to lower the risk of reactivation of latent virus. The varicella vaccine may eventually reduce or eliminate herpes zoster, which is a serious problem for elderly and immunocompromised individuals.

The varicella vaccine. Clinical trials in immunocompromised individuals

A review of the use of live attenuated varicella vaccine in immunocompromised children, particularly those with underlying leukemia in remission, is presented. Data concerning safety, immunogenicity, and efficacy of this vaccine in high-risk children are reviewed. The unique contributions toward our understanding of varicella vaccine, including spread of vaccine-type virus, incidence of zoster, and immune correlates provided by studies of immunocompromised patients are discussed. The importance of protecting high-risk children against severe varicella by the use of varicella vaccine is apparent.

Modified varicella-like syndrome

After incidental exposure to natural varicella, up to 18% of vaccinees reported a breakthrough infection known as modified varicella-like syndrome (MVLS) over up to 10 years of postvaccination follow-up, compared with natural varicella occurring in similarly aged unvaccinated children at the rate of 9% per year. Children with MVLS are frequently asymptomatic, and their disease is characterized by having fewer lesions, less fever, and lasting fewer days than natural varicella. When a case of MVLS occurs there are few secondary cases, suggesting that it is infrequently transmitted. Sequelae such as secondary bacterial infection, cerebellar ataxia, encephalitis, and pneumonia occur infrequently.

The varicella vaccine. Vaccine development

In this article, rationales and method of development of attenuated live varicella (Oka) vaccine are described, with biologic and biophysical characteristics of the vaccine virus. The results of early clinical trials in Japan are also described, along with the results of detection of viremia in vaccinees and a follow-up of incidence of zoster in acute leukemic children, which indicate possible immunopathogenesis of varicella and zoster.

Varicella-zoster virus

Varicella-zoster virus (VZV) is a ubiquitous human alphaherpesvirus that causes varicella (chicken pox) and herpes zoster (shingles). Varicella is a common childhood illness, characterized by fever, viremia, and scattered vesicular lesions of the skin. As is characteristic of the alphaherpesviruses, VZV establishes latency in cells of the dorsal root ganglia. Herpes zoster, caused by VZV reactivation, is a localized, painful, vesicular rash involving one or adjacent dermatomes. The incidence of herpes zoster increases with age or immunosuppression. The VZV virion consists of a nucleocapsid surrounding a core that contains the linear, double-stranded DNA genome; a protein tegument separates the capsid from the lipid envelope, which incorporates the major viral glycoproteins. VZV is found in a worldwide geographic distribution but is more prevalent in temperate climates. Primary VZV infection elicits immunoglobulin G (IgG), IgM, and IgA antibodies, which bind to many classes of viral proteins. Virus-specific cellular immunity is critical for controlling viral replication in healthy and immunocompromised patients with primary or recurrent VZV infections. Rapid laboratory confirmation of the diagnosis of varicella or herpes zoster, which can be accomplished by detecting viral proteins or DNA, is important to determine the need for antiviral therapy. Acyclovir is licensed for treatment of varicella and herpes zoster, and acyclovir, valacyclovir, and famciclovir are approved for herpes zoster. Passive antibody prophylaxis with varicella-zoster immune globulin is indicated for susceptible high-risk patients exposed to varicella. A live attenuated varicella vaccine (Oka/Merck strain) is now recommended for routine childhood immunization.