Varicella vaccination--a critical review of the evidence

Safety of varicella vaccination strategies: An overview of reviews

The safety of new vaccines under development as well as existing vaccines is a key priority for national and international public health agencies. A number of countries have implemented universal childhood varicella vaccination programmes over the past 30 years. However, strategies differ in terms of the number of doses, type of vaccine(s) recommended, age at vaccination and interval between doses for a two-dose schedule. An overview of reviews was undertaken to assess the existing systematic review evidence of the safety of varicella vaccination strategies. The review was restricted to immunocompetent children aged 9 months to 6 years inclusive. A comprehensive search of databases, registries and grey literature was conducted up to 2 February 2022. Two reviewers independently screened, extracted data and assessed the methodological quality of included reviews. Overlap of included reviews was also assessed. A total of 17 reviews, incorporating both the monovalent varicella only and quadrivalent measles-mumps-rubella-varicella (MMRV) vaccines were included in the overview; six assessed the safety of one-dose strategies, four assessed the safety of two-dose strategies and 14 reviews did not specify the dosing strategy. The evidence suggests that mild local and systemic reactions are relatively common with varicella vaccination. Febrile seizures are also possible adverse effects of both the monovalent and quadrivalent MMRV vaccine, but serious adverse reactions are rare. While most reviews contained methodological flaws, and analysis by vaccine type and dosing strategy was restricted due to lack of detail in reporting of the reviews, there was clear and consistent evidence from a substantial evidence base, comprising 34 randomised controlled trials and 62 other primary studies/reviews, that varicella vaccination is safe.

Clinical efficacy and effectiveness of alternative varicella vaccination strategies: An overview of reviews

A number of countries have implemented universal childhood varicella vaccination programmes over the past 30 years. However, strategies differ in terms of dosing schedule (one- or two-dose), type of vaccine(s) recommended (monovalent, quadrivalent measles-mumps-rubella-varicella, or both), age at vaccination, and dosing interval for a two-dose schedule. An overview of reviews was undertaken to assess the existing systematic review evidence of the clinical efficacy/effectiveness of alternative varicella vaccination strategies. A comprehensive search of databases, registries and grey literature was conducted up to 2 February 2022. Two reviewers independently screened, extracted data and assessed the methodological quality of included reviews. A total of 20 reviews were included in the overview; 17 assessed the efficacy/effectiveness of one-dose strategies and 10 assessed the efficacy/effectiveness of two-dose strategies. Although the quality of most reviews was deemed 'critically low', there was clear and consistent evidence that vaccination is very effective at reducing varicella. While the analysis was restricted due to lack of detail in reporting of the reviews, the evidence suggests that two-dose strategies are more efficacious/effective than one-dose strategies in preventing varicella of any severity, but that both strategies have similar high efficacy/effectiveness in preventing moderate or severe varicella. Based on this evidence in this overview of reviews, a key consideration for policymakers on the possible introduction of a childhood varicella vaccination programme and the choice between a one- or two-dose strategy, will be whether the objective of a programme is to prevent varicella of any severity or to prevent moderate to severe varicella.

Immunogenicity of varicella zoster vaccine in pediatric liver transplantation

BACKGROUND

Pediatric liver transplant (LT) candidates often miss complete varicella-zoster virus (VZV) vaccination before LT. We aimed to evaluate the immunogenicity of two doses of VZV vaccines in pediatric LT candidates younger than 2 years and persistence of its immunogenicity after LT.

METHODS

Patients aged 9-24 months were enrolled before LT. The first dose of VZV vaccine was given at 9 months, and the second dose was given at between 1 to 3 months later, and at least 4 weeks before LT. Varicella-zoster IgG (VZG) was used to detect immunoglobulin G antibodies to VZV and was reported as a test value (TV). A test value ≥ 0.9 was considered as seropositive. TV was measured at enrollment, 1 month after the first and the second dose of VZV vaccine, before LT, and 3 and 6 months after LT.

RESULTS

Fourteen children were enrolled in this prospective cohort study. The median age at the first and the second dose of VZV vaccine was 11.5 months (IQR 9-12) and 13 months (IQR 12-33), respectively. The seroconversion rate was 66.7% (8/12) and 70% (7/10) after the first and second VZV vaccine doses, respectively. Seven of nine patients who underwent LT had two doses of VZV vaccine. Six patients were seropositive before LT, which persisted at 3 to 6 months after LT. Of two patients who received only one dose, TV was not detected after LT.

CONCLUSIONS

The two doses of VZV vaccine appeared to be more immunogenic than one dose in pediatric LT candidates aged less than 2 years.

Lack of persisting antibody in a post-transplant patient after vaccine-strain varicella

BACKGROUND

LAVV have historically been avoided in children after solid organ transplantation. However, it has been reported that post-transplant, children without severe immunosuppression can generate anti-varicella antibody after immunization but the duration of the response is not clear. Furthermore, the origin of the varicella virus in immunosuppressed patients who develop varicella after vaccination is often unclear.

CLINICAL PROGRESS

A female child received LAVV 30 months after a living donor liver transplant at the age of 2 months. Varicella rash appeared on the trunk 16 days after vaccination and gradually spread over the body. The patient was treated with intravenous acyclovir followed by oral therapy and recovered fully. The virus detected in blisters was derived from the vaccine-type strain. Paired sera before and after the onset of varicella showed an increase in antibody titer. However, 2 years after onset, the antibody titer decreased to undetectable again.

CONCLUSIONS

This was an informative case of varicella due to vaccine strain attenuated virus. Antibody levels were not maintained over many years. Although varicella was caused by the vaccine-type strain, repeated vaccinations may be necessary for post-transplant patients who develop varicella.

Health Impact and Cost-effectiveness Assessment for the Introduction of Universal Varicella Vaccination in Switzerland

BACKGROUND

Varicella, caused by the varicella-zoster virus, is a highly contagious infectious disease with substantial health and economic burden to society. Universal varicella vaccination (UVV) is not yet recommended by the Swiss National Immunization Program, which instead recommends catch-up immunization for children, adolescents and adults 11-40 years of age who have no reliable history of varicella or are varicella-zoster virus-IgG seronegative. The objective of this study was to perform an assessment of health impact and cost-effectiveness comparing UVV with current practice and recommendations in Switzerland.

METHODS

A dynamic transmission model for varicella was adapted to Switzerland comparing 2 base-case schedules (no infant vaccination and 10% coverage with infant vaccination) to 3 different UVV schedules using quadrivalent (varicella vaccine combined with measles-mumps-rubella) and standalone varicella vaccines administered at different ages. Modeled UVV coverage rates were based on current measles-mumps-rubella coverage of approximately 95% (first dose) and 90% (second dose). Direct medical costs and societal perspectives were considered, with cost and outcomes discounted and calculated over a 50-year time horizon.

RESULTS

UVV would reduce the number of varicella cases by 88%-90%, hospitalizations by 62%-69% and deaths by 75%-77%. UVV would increase direct medical costs by Swiss Franc (CHF) 39-49 (US $43-54) per capita and costs from a societal perspective by CHF 32-40 (US $35-44). Incremental quality-adjusted life-years per capita increased by 0.0012-0.0014. Incremental cost-effectiveness ratios for the UVV schedules versus the base-case were CHF 31,194-35,403 (US $34,452-39,100) per quality-adjusted life-year from the direct medical cost perspective and CHF 25,245-29,552 (US $27,881-32,638) from the societal perspective.

CONCLUSIONS

UVV appears highly effective and cost-effective when compared with current clinical practice and recommendations in Switzerland from both a direct medical costs perspective and societal perspective.

Hospitalization for acute cerebellitis in children affected by varicella: how much does it cost?

Background

Chickenpox is a highly contagious airborne disease caused by the varicella zoster virus. It is generally benign and self-limiting, but it may be responsible of life-threatening complications. Acute cerebellitis (AC) is the most common neurological complication and is associated with prolonged hospitalization in the acute phase (HAP).

Aim of the study

To estimate the costs of AC HAP in children affected by varicella.

Materials and methods

We retrospectively reviewed the medical records of a pediatric cohort hospitalized for chickenpox AC over a period of 15 years (from October 2003 to October 2018) and we analyzed acute care costs. For any patient the HAP has been calculated. The final value includes cost of hospital accommodation and management at the Pediatric and Infectious Diseases Unit. To this cost, the price of procedures (imaging, laboratory exams, medical and paramedical evaluations) and medical treatments was added.

Results

In the study period, 856 children had been hospitalized for varicella. Out of them, 65 met a diagnosis of AC and were included in the study. The hospitalization length was of 10 days (range 3–20 days). The median cost of HAP for each patient was of 5366 euro, with an average annual cost of 23,252 €. The most significant part of HAP is due to the cost of hospital accommodation and management at the Pediatric Infectious Diseases Unit, which was about € 537.78 for a single day.

Discussion

Although AC post-varicella is rare, its HAP cost is not negligible resulting in substantial economic burden. Vaccination would have probably prevented varicella and AC complication, avoiding hospitalization.

Conclusions

Financial studies are important for evaluate the cost saving in order to influence public funding decisions. Further studies are necessary to investigate the economic burden of the disease.

Preventive effectiveness of varicella vaccine in healthy unexposed patients

INTRODUCTION

Chickenpox is an infectious disease caused by varicella-zoster virus. Varicella vaccine is conventionally used for its prevention, and its administration seeks to reduce the onset of the disease and complications associated. However, there is still controversy about its effectiveness.

METHODS

We searched in Epistemonikos, the largest database of systematic reviews in health, which is maintained by screening multiple information sources, including MEDLINE, EMBASE, Cochrane, among others. We extracted data from the systematic reviews, reanalyzed data of primary studies, conducted a meta-analysis and generated a summary of findings table using the GRADE approach.

RESULTS AND CONCLUSIONS

We identified two systematic reviews including 16 studies overall, of which three were randomized trials. We concluded that the varicella vaccine decreases the risk of contracting the disease in the long term and probably reduces the risk of developing the disease in the short term in healthy unexposed patients. Nevertheless, the vaccination increases the occurrence of local reactions 48 hours after its administration and probably increases the presence of fever and chickenpox-like rash.

Safety and immunogenicity of a varicella vaccine without human serum albumin (HSA) versus a HSA-containing formulation administered in the second year of life: a phase III, double-blind, randomized study

BACKGROUND

A new formulation of the live-attenuated varicella vaccine Varilrix (GSK) produced without human serum albumin (HSA) was developed to minimize a theoretical risk of transmission of infectious diseases. A previous study showed that the vaccine was immunologically non-inferior to the HSA-containing vaccine and well-tolerated in toddlers; low-grade fever was numerically higher in children receiving the vaccine without HSA, but the study lacked power to conclude on this difference.

METHODS

In this phase III, double-blind, multi-center study, healthy 12-23-month-olds were randomized (1:1) to receive two doses of the varicella vaccine without (Var-HSA group) or with HSA (Var + HSA group) at days 0 and 42. The primary objective compared safety of the vaccines in terms of incidence of fever > 39.0 °C in the 15-day period post-first vaccination. The objective was considered met if the upper limit of the 95% confidence interval for the between-group difference in the incidence of fever > 39.0 °C was ≤5% (Var-HSA group minus Var + HSA group). Safety, reactogenicity and immune responses were evaluated.

RESULTS

Six hundred fifteen children in the Var-HSA group and 616 in the Var + HSA group received ≥1 vaccination. Fever > 39.0 °C was reported in 3.9 and 5.2% of participants in the Var-HSA and Var + HSA groups, with a between-group difference of - 1.29 (95% confidence interval: - 3.72-1.08); therefore, the primary objective was achieved. Fever rates post-each dose and the incidence of solicited local and general adverse events (AEs) were comparable between groups. Unsolicited AEs were reported for 43.9 and 36.5% of children in the Var-HSA group and 45.8 and 36.0% of children in the Var + HSA group, during 43 days post-dose 1 and 2, respectively. Serious AEs occurred in 2.1% (group Var-HSA) and 2.4% (group Var + HSA) of children, throughout the study. In a sub-cohort of 364 children, all had anti-varicella-zoster virus antibody concentrations ≥50 mIU/mL post-dose 2; comparable geometric mean concentrations were observed between the groups.

CONCLUSIONS

The varicella vaccine formulated without HSA did not induce higher rates of fever during the 15 day-post-vaccination period, as compared with the original HSA-containing vaccine. The two vaccines displayed similar safety and immunogenicity profiles in toddlers.

TRIAL REGISTRATION

NCT02570126 , registered on 5 October 2015 (www.clinicaltrials.gov).

Safety, immunogenicity, and lot-to-lot consistency of live attenuated varicella vaccine in 1-3 years old children: a double-blind, randomized phase III trial

The study was to evaluate the safety, immunogenicity and lot-to-lot consistency of live attenuated varicella vaccine in Chinese population aged 1-3 years. The double-blind, randomized phase III trial was conducted in Henan Province, China. In total, 1197 subjects were included in this study. Subjects were randomly assigned into four groups in a 2:2:2:1 ratio to receive one of the three lots of commercial scale (CS) vaccine or the licensed pilot scale (LPS) vaccine. Seroconversion rate and neutralizing antibody titers (NATb) were assessed at day 0 pre-vaccination and at day 30 post-vaccination. Safety data were recorded for 30 days post-vaccination. After vaccination, the geometric mean titers (GMTs) of the three CS groups were 25.04 (95% confidence interval [CI], 22.85 to 27.44), 24.47 (95% CI, 22.35 to 26.78) and 25.88 (95% CI, 23.61 to 28.36), respectively (P= 0.6928). The ratio of GMTs adjusted for covariates of each pair of lots were all between 0.67 to 1.50 in susceptible subjects. The difference of seroconversion rate between pooled CS group and LPS group was 3.82 (95% CI, 0.55 to 8.81). Meanwhile, the percentage of solicited local, systemic and unsolicited adverse reactions showed no difference across the four groups, and most of the adverse reactions were mild or moderate in intensity. The CS group was comparable to the LPS group in safety and immunogenicity. The consistency of three consecutive CS lots was reliable. Moreover, the CS group was non-inferior to the LPS group.

Microbiology laboratory and the management of mother-child varicella-zoster virus infection

Varicella-zoster virus, which is responsible for varicella (chickenpox) and herpes zoster (shingles), is ubiquitous and causes an acute infection among children, especially those aged less than six years. As 90% of adults have had varicella in childhood, it is unusual to encounter an infected pregnant woman but, if the disease does appear, it can lead to complications for both the mother and fetus or newborn. The major maternal complications include pneumonia, which can lead to death if not treated. If the virus passes to the fetus, congenital varicella syndrome, neonatal varicella (particularly serious if maternal rash appears in the days immediately before or after childbirth) or herpes zoster in the early years of life may occur depending on the time of infection. A Microbiology laboratory can help in the diagnosis and management of mother-child infection at four main times: (1) when a pregnant woman has been exposed to varicella or herpes zoster, a prompt search for specific antibodies can determine whether she is susceptible to, or protected against infection; (2) when a pregnant woman develops clinical symptoms consistent with varicella, the diagnosis is usually clinical, but a laboratory can be crucial if the symptoms are doubtful or otherwise unclear (atypical patterns in immunocompromised subjects, patients with post-vaccination varicella, or subjects who have received immunoglobulins), or if there is a need for a differential diagnosis between varicella and other types of dermatoses with vesicle formation; (3) when a prenatal diagnosis of uterine infection is required in order to detect cases of congenital varicella syndrome after the onset of varicella in the mother; and (4) when the baby is born and it is necessary to confirm a diagnosis of varicella (and its complications), make a differential diagnosis between varicella and other diseases with similar symptoms, or confirm a causal relationship between maternal varicella and malformations in a newborn.

Varicella vaccine without human serum albumin versus licensed varicella vaccine in children during the second year of life: a randomized, double-blind, non-inferiority trial

Background

GSK’s varicella vaccine contains human serum albumin (HSA) which is used to stabilize the virus and prevent immunogens from adhering to the injection vial walls. However, because HSA is derived from human blood, there is a theoretical risk that it might contain infectious agents which could be unsafe for humans. Given this concern, a study was undertaken to compare the immunogenicity and safety of a new formulation without HSA with the currently licensed varicella vaccine in the Czech Republic and Hungary.

Methods

Healthy children aged 11–21 months received two doses of the varicella vaccine either with or without HSA. Antibody titres against varicella-zoster virus (anti-VZV) were measured 42 days after each dose, using an immunofluorescence assay (IFA, cut-off = 4dilution⁻¹) and enzyme linked immunosorbent assay (ELISA, cut-off = 25 mIU/ml). Solicited local symptoms were recorded during a 4-day post-vaccination follow-up period; solicited general and unsolicited symptoms were recorded during a 43-day post-vaccination follow-up period and serious adverse event (SAEs) were recorded throughout the study.

Results

Of 244 children (mean age = 15.2 months [SD = 3.2]) vaccinated in the study, 233 (vaccine without HSA N = 117; vaccine containing HSA N = 116) formed the according-to-protocol immunogenicity cohort. Observed seroconversion/seroresponse rates were >98 and 100 %, 42 days after doses 1 and 2, respectively. The rates were within the same range in both groups, irrespective of the testing assay. The varicella vaccine without HSA was non-inferior to the licensed vaccine in terms of anti-VZV antibody Geometric Mean Titre/Concentration ratio (1.12 [95 % CI:0.86–1.46] by IFA; 1.12 [95 % CI:0.93–1.33] by ELISA) approximately six weeks after the first dose of the 2-dose vaccination course. The incidence of solicited and unsolicited symptoms was similar after both vaccines; low-grade fever was numerically higher after the first dose of the varicella vaccine without HSA. Seven SAEs were reported, none of which were fatal or considered to be vaccine-related.

Conclusions

The first dose of a new varicella vaccine without HSA was immunologically non-inferior to the licensed varicella vaccine. After two doses, both vaccines had acceptable safety profiles in children aged 11–21 months in the Czech Republic and Hungary.

Trial registration

NCT00568334, registered on 5 December 2007 (www.clinicaltrials.gov).

The impact of ten years of infant universal Varicella vaccination in Sicily, Italy (2003-2012)

INTRODUCTION

Universal varicella vaccination in Sicily was introduced in infant population since 2003, with a rapidly increasing coverage. Aim of the present study was to analyze changes in the epidemiology of varicella since the introduction of universal vaccination.

METHODS

The study was performed by analyzing Sicilian administrative/clinical data on varicella case notifications and hospitalizations from 2003 to 2012 (ICD-9-CM discharge diagnosis codes 052 and 052.×). MMR+V and V coverage were also calculated for each birth cohort. Moreover, blood samples drawn in 2013/2014 from general population stratified by age were tested for varicella antibodies.

RESULTS

From 2003 to 2012, 15 433 varicella cases were notified with a decreasing temporal trend (1.1/1000 population in 2003 to 0.1/1000 in 2012) (P < 0.001). In the same period, a total of 1145 patients were hospitalized with a diagnosis of varicella, with a 6-fold reduced risk of hospitalization over time (from 4.8 to 0.8/100 000 population per year; P < 0.001). Varicella vaccination coverage rates increased from 40% (2001 birth cohort) to 85% (2010 birth cohort), and inversely correlated with both notification and hospitalization rates (P < 0.001). Finally, 80.0% of subjects enrolled in the seroepidemiological survey were positive for varicella and seroprevalence increased significantly with age in both sexes (P < 0.001).

DISCUSSION

The results show the impact of infant universal varicella vaccination in Sicily. Noteworthy, notifications and hospitalizations for varicella have significantly decreased after the introduction of universal vaccination, confirming the effectiveness of the adopted strategy.

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.

The effectiveness of varicella vaccination in children in Germany: a case-control study

BACKGROUND

Effectiveness of 1 dose of varicella vaccination was estimated to be 85-88% against clinical varicella of any severity in case-control studies in non-European countries, but lower effectiveness has been demonstrated in outbreaks.

METHODS

A prospective, age- and practice-matched case-control study was conducted in Germany to assess the effectiveness of 1 dose of OKA/GSK varicella vaccine (derived from the OKA strain, a Japanese clinical isolate) and of any varicella vaccine (including OKA/GSK, OKA/Merck and MMR-OKA/GSK) against polymerase chain reaction (PCR)-confirmed varicella under conditions of routine use.

RESULTS

The cohort included 432 PCR-confirmed cases and 432 matched controls (1-7 years old). Varicella vaccination was reported for 13.2% (57/432) of cases and 45.1% (195/432) of controls. Median time since vaccination was 28 and 25 months, respectively. Vaccinated cases experienced milder disease (P < 0.0001) and shorter duration of disease (P = 0.004) compared with unvaccinated cases. After adjusting for gender and school/day-care attendance, vaccine effectiveness of 1 dose of OKA/GSK against PCR-confirmed varicella of any severity was 71.5% (95% confidence interval [CI]: 49.1-84.0) and 94.7% (95% CI: 77.8-98.7) against PCR-confirmed moderate or severe varicella. Adjusted effectiveness for any varicella vaccine was 86.4% (95% CI: 77.3-91.8) against any severity and 97.7% (95% CI: 90.5-99.4) against moderate or severe varicella.

CONCLUSIONS

One dose of varicella vaccine provided high protection against moderate and severe varicella disease for a period of up to 5 years after vaccination. However, further effectiveness data are needed to assess long-term protection.

Varicella-zoster immunization in pediatric liver transplant recipients: safe and immunogenic

Varicella can have a severe course in immunosuppressed patients. Although prevention is fundamental, live-attenuated varicella-zoster (VZV) vaccine is not currently recommended in transplant recipients. Our aims were to (1) evaluate VZV immunity in pediatric liver transplant (LT) recipients; (2) immunize (two doses) seronegative patients post-LT; (3) monitor vaccine safety, (4) assess B and T cell vaccine responses. All patients followed at the Swiss National Pediatric LT Center were approached and 77/79 (97.5%) were enrolled (median age 7.8 years). Vaccine safety was monitored by standardized diary cards and phone calls. VZV-specific serology and CD4(+) T cells were assessed before and after immunization. Thirty-nine patients (51.1%) were seronegative including 14 children immunized pre-LT. Thirty-six of 39 seronegative patients were immunized post-LT (median 3.0 years post LT). Local (54.8%) and systemic (64.5%) reactions were mild and transient. The frequency of VZV-specific CD4(+) T cells and antibody titers increased significantly (respectively from 0.085% to 0.16%, p = 0.04 and 21.0 to 1134.5 IU/L, p < 0.001). All children reached seroprotective titers and 31/32 (97%) patients assessed remained seroprotected at follow-up (median 1.7 years). No breakthrough disease was reported during follow-up (median 4.1 years). Thereby, VZV vaccine appears to be safe, immunogenic and provide protection against disease in pediatric LT patients.

Seroepidemiology of varicella-zoster virus and reliability of varicella history in Turkish children, adolescents and adults

This study aimed to assess the age specific varicella-zoster virus (VZV) seroprevalence in Izmir, Turkey and to determine the reliability of a history of varicella to detect susceptible children, adolescents and adults. A questionnaire, including previous history of varicella, was completed for each participant and, in 590 of them, VZV-specific IgG was measured using an ELISA test. Overall, 28.5% of individuals were seronegative for VZV. By 5 years of age, only 25.5% of children were seropositive for VZV. Among adolescents and young adults, 18.8% and 11.7% were seronegative, respectively. The negative predictive value was 57.8%, decreasing with age (81.9% in children, 34.5% in adolescents and 8.3% in adults). In conclusion, a negative history of varicella is not a reliable predictor of varicella antibody status in adolescents and young adults. Serological testing before immunisation will be logical, rather than presumptive vaccination, for adolescents and adults with negative history of varicella.

Chickenpox

INTRODUCTION

Chickenpox is extremely contagious. Over 90% of unvaccinated people become infected, but infection occurs at different ages in different parts of the world - over 80% of people have been infected by the age of 10 years in the US, the UK, and Japan, and by the age of 20 to 30 years in India, South East Asia, and the West Indies.

METHODS AND OUTCOMES

We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of interventions to prevent chickenpox in healthy adults and children? What are the effects of interventions to prevent chickenpox in children exposed prenatally? What are the effects of interventions to prevent chickenpox in immunocompromised adults and children? What are the effects of treatments for chickenpox in healthy adults and children? What are the effects of treatments for chickenpox in immunocompromised adults and children? We searched: Medline, Embase, The Cochrane Library, and other important databases up to June 2010 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).

RESULTS

We found 11 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.

CONCLUSIONS

In this systematic review we present information relating to the effectiveness and safety of the following interventions: aciclovir, famciclovir, live attenuated vaccine, valaciclovir, and varicella zoster immunoglobulin.

Intrathecal steroid therapy for postherpetic neuralgia: a review

Two recent publications advocated intrathecal injection of methylprednisolone acetate for postherpetic neuralgia. Conceptually, these therapeutic trials were based on the failed assumption that chronic inflammation persists in dorsal root ganglia even after the lesions of acute zoster have healed. Constructionally, these publications can be criticized on numerous grounds: cranial zoster was excluded, follow up periods were too short, dangers or reactivating the varicella virus were ignored, no methylprednisolone acetate-only group was included, pharmacological dangers of intrathecal lidocaine were overlooked. In addition to these basic conceptual deficiencies, multiple dangers of intrathecal methylprednisolone (therapeutically and by accidental injection) are manifest in a literature dating back over two decades in which several hundred serious complications are described. In summary, all rational evidence indicates that this treatment should not be prescribed.

Varicella complications: Is it time to consider a routine varicella vaccination?

Background/Aim. Varicella is a common and benign disease of childhood. Complications are rare, but in some patients, even without risk factors, severe, life threatening complications could be seen. The aim of this study was to establish the type and frequency of varicella complications among hospitalized patients over an 8-year period. Methods. This retrospective analysis included medical charts of the patients hospitalized in the Infectious Disease Clinic, Belgrade, Serbia, from 2001-2008 (4.85% of all registered patients with varicella in Belgrade, 2001-2008). Among hospitalised patients dermografic characteristics were analyzed: hospitalisation lenght, presence and type of complications, presence of immunocompromising conditions and outcome of the disease. The diagnosis of varicella was made on clinical grounds, and in persons > 40 years, with negative epidemiological data of contacts, serological confirmation (ELISA VZV IgM/IgG BioRad?) and avidity of IgG antibodies were done to exclude the possibility of disseminated herpes zoster. Results. A total of 474 patient were hospitalized over an 8-year period. The age of patients was from 5 months to 75 years (mean 22.4 ? 16.1, median 23.5 years). The majority of patients were adults (n = 279; 58.9%) and 195 (41.1%) patients were ? 15 years old. Complications were found in 321/474 (67.7%) patients. The registered complications were: varicella pneumonia (n = 198; 41.38%), bacterial skin infections (n = 40; 8.4%), cerebelitis (n = 28; 5.9%), bacterial respiratory infection (n = 21; 4.4%), viral meningitis (n = 10; 2.31%), encephalitis (n = 9; 1.9%), thrombocytopenia (n = 2; 0.4%); 11 (2.3%) patients had more than one complication, among them were sepsis, myopericarditis and retinal hemorrhages. When complications were analyzed according to the age, there were no statistical significance, but when type of complication was analyzed statistical significance was found (p < 0.05). In adults, pneumonia was the most common complication: 173/279 (62%), followed by skin infections (2.9%), bacterial respiratory infections (2,2%), and more than one complication (2.3%). Pneumonia was more common in adults than in children (7 : 1). In children skin infections were the most common complications (16.4%), followed by cerebelitis (13.3%), viral pneumonia (12.8%), bacterial respiratory infections (7.7%), encephalitis (3.6%), and more than one complication (4.1%). Neuroinfections were more common in children than in adults (6:1), as well as bacterial skin infections (4 : 1). Two patients died (0,4%). Conclusion. There was no difference in the incidence of varicella complication in children and adults, but the type of complication differed. In children the most common complications were skin and neurological infections, while in adults it was varicella pneumonia. These data provide a baseline for estimating the burden of varicella in Belgrade and support the inclusion of varicella vaccine in childhood immunisation program in Serbia.

Chickenpox in varicella IgG positive patients: experience of a regional paediatric oncology centre

Aciclovir prophylaxis was previously given to all immunocompromised patients treated by our unit, following contact with varicella zoster. In 2003, we changed practice according to National Guidelines, giving prophylaxis only to patients without serum varicella zoster immunoglobulin G antibody (VZ IgG) at diagnosis of their malignancy. Since then we have seen nine patients with acute lymphoblastic leukaemia (ALL) and VZ IgG positivity at diagnosis of their malignancy develop chickenpox. Our observations question current practice for patients with ALL.

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.

Safety, tolerability, and immunogenicity of a two-dose regimen of high-titer varicella vaccine in subjects ≥13 years of age

A new manufacturing process, known as process upgrade varicella vaccine (PUVV) was developed for a refrigerated formulation of varicella vaccine and for an investigational zoster vaccine. Safety and tolerability of a two-dose regimen of high-titered (approximately 50,000 PFU) PUVV were compared to a lower-titer formulation (approximately 5400 PFU) of VARIVAX; in 1366 healthy subjects > or =13 years old. Only one vaccine-related clinical serious adverse experience (pruritus; no hospitalization) was reported, in the VARIVAX group. Injection-site adverse experiences following any dose were higher in the PUVV group, 70.0%, than in the VARIVAX group, 56.2%, but generally were mild. Immunogenicity were similar in both groups in seronegative subjects. PUVV was generally well tolerated, and elicited an immune response similar to that induced by the marketed formulation of VARIVAX.

Determining the rate of varicella vaccine rash in children with moderate-severe eczema

OBJECTIVES

To determine the rate and severity of vesicular reactions following varicella vaccine in children with moderate-severe eczema. Secondary endpoints included the rates and severity of local reactions and eczema severity change within 42 days of vaccination.

METHODS

Prospective open intervention pilot study of varicella vaccine in children aged 12 months to 13 years with moderate-severe eczema. Children were given varicella vaccine alone and followed for 42 days after vaccination.

RESULTS

Fifty children, aged 12 months to 10.5 years were recruited, with complete follow-up for 48. A vesicular rash with a single lesion occurred in one child (2.1% (95% CI: 0, 11.1%)), 10 days following vaccination. Local reactions, including erythema, swelling and tenderness, were reported in eight children (16.7%). A flare-up of moderate-severe generalized eczema was reported in one child (2.1%) during the first week following varicella vaccine.

CONCLUSIONS

Vesicular rash and local reactions following varicella vaccination were no more common or severe in children with moderate-severe eczema than that reported in the published literature in children without eczema. Eczema in the 42 days following vaccination did not appear to increase in severity.

Hospitalizaciones por varicela en el Hospital Infantil La Fe (Valencia 2001-2004)

INTRODUCTION

Varicella is a common, highly contagious disease. It is usually benign but has potentially serious complications.

PATIENTS AND METHODS

To assess the clinical characteristics and the associated cost of varicella hospitalization, we reviewed the medical records of children hospitalized for varicella between 2001 and 2004. Children with coincidental varicella hospitalized for a different reason were excluded.

RESULTS

Of 1177 children with varicella attended at the emergency room, 101 (8.6 %) were hospitalized. The median age was 3.2 years (21 days to 18.9 years). Twenty-eight children had underlying disease. Thirty-seven children had no complications and the reason for admission was: a) risk of severe varicella (21 immunocompromised children, three neonates), and b) high fever or observation (13 cases). The 64 remaining children were admitted for 66 complications of varicella. The most common complications were skin/soft tissue infections (33 patients) and the leading cause was Streptococcus pyogenes (n = 13) and Staphylococcus aureus (n = 10) isolated in blood or the site of infection. Other complications were pneumonia (13 children), neurological (febrile seizures in nine, meningoencephalitis in two, acute disseminated encephalomyelitis in one, cerebellitis in one), hematological (neutropenia in one, Henoch-Schönlein purpura in one and thrombopenic purpura in three) and osteoarticular (synovitis in one and septic arthritis in one). One patient died of multiorgan failure. During the study period, the rate of emergency room visits due to varicella doubled and the number of admissions for complications tripled. The mean length of hospital stay was 6.8 days (range: 1-28 days) and the total associated cost was 397,314.14 Euro, excluding symptomatic treatment.

CONCLUSIONS

The high morbidity associated with varicella and its complications, as well as the high social costs of this disease, support the implementation of routine varicella vaccination. This could reduce the total number of cases, their severity, direct costs, generated by medical care, and indirect costs, generated by the disease and hospitalization.

Evidenzbasierte Therapie von Herpes-Virus-Erkrankungen der Haut

Six questions regarding varicella-zoster virus-related skin diseases are addressed. The Cochran Library, MEDLINE, Clinical Evidence and several guideline providers were searched for evidence. The level of evidence in papers was appraised according to the Oxford Centre for Evidence-based Medicine Levels of Evidence. The current evidence for antiviral therapy of chickenpox in immunocompetent children, adults and pregnancy, recommendation of varicella vaccination, effect of time of initiation of antiviral therapy in acute zoster as well as route of treatment with regard to onset of post-zoster neuralgia are covered.

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.

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.

The societal value of universal childhood vaccination

Availability of new vaccines preventing infectious diseases in healthy children populations is increasing worldwide. In Canada, despite the current recommendation of the National Advisory Committee on Immunization to include recent vaccines in routine schedule, only a few provinces have incorporated some of the newer vaccines in routine vaccination programs. A review was undertaken of economic evaluations of childhood vaccination strategies performed from the societal point of view in industrialized countries, to gain perspective on their global benefits. The general trend supports most universal vaccination programs as cost-saving or cost-effective for society. Comparison of vaccination programs with other health care interventions indicates that vaccines are often one of society's best healthcare investments. Current data suggest that the Canadian society would benefit from a more complete immunization program.

Safety of live viral vaccines in patients with chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome)

The package inserts of live viral vaccines include immunodeficiency as a contraindication. Nevertheless, patients with mild forms of immunodeficiency may benefit from vaccination. No published guidelines exist for the administration of these vaccines specifically to patients with chromosome 22q11.2 deletion syndrome. This syndrome is also sometimes called DiGeorge syndrome and is associated with thymic hypoplasia and diminished T-cell numbers and has a wide spectrum of phenotypic features that include cardiac anomalies, dysmorphic facial features, and hypocalcemia. Patients generally exhibit a mild to moderate decrement in T-cell numbers with preservation of T-cell function. The aims of this study were to investigate the incidence of side effects after live viral vaccine administration in a population with chromosome 22q11.2 deletion syndrome. The high frequency of this syndrome in the population (1:3000 children) mandates a greater understanding of the risks and benefits related to live viral vaccine administration. A retrospective analysis of vaccine adverse events was performed. The data acquisition form evaluated the frequency of live vaccine administration and the consequences of both vaccination and withholding the vaccine. Flow cytometric enumeration of T cells was performed as part of an immunologic evaluation. Thirty-two of 59 responders were vaccinated with the varicella vaccine. Only 9% of patients reported adverse events. However, 63% of unvaccinated children developed chickenpox. Comparison of patients who tolerated the vaccine with those who reported adverse events showed no statistically significant differences in current age (7 vs 5.7 years), age at vaccination (3 vs 2.5 years), or T-cell subset counts: CD3 (1951 vs 2083 cells/ microL), CD4 (1283 vs 1463 cells/ microL), and CD8 (530 vs 502 cells/ microL). Fifty-two of 59 responders were vaccinated with measles-mumps-rubella (MMR). Twelve (23%) of 52 reported mild side effects, including fever, rash, and constitutional symptoms. No severe adverse reactions were reported. No patient reported natural disease with measles, mumps, or rubella. There were no statistically significant differences between the T-cell counts in the vaccinated group reporting side effects versus the vaccinated group without side effects (mean CD3 counts: 1928 vs 1736 cells/ microL; CD4 counts: 1250 vs 1127 cells/ microL; and CD8 counts: 528 vs 483 cells/ microL). In our study, patients with chromosome 22q11.2 deletion syndrome had a similar incidence of adverse effects with varicella and MMR vaccines compared with that reported in the general population. All side effects were mild. However, in patients who did not receive the varicella vaccine, an overwhelming 63% contracted the disease. Patients who were not vaccinated against MMR did not develop natural disease. The data suggest that this is a cohort of patients with 22q11.2 deletion syndrome who have tolerated live viral vaccinations without evidence of significant side effects. A prospective study could address whether there are T-cell thresholds below which vaccination is unsafe; however, the information that we present suggests that vaccinating children with chromosome 22q11.2 deletion with live viral vaccines does not carry a significantly higher risk of adverse reactions compared with the general population, provided that they have no evidence of severe immunocompromise.

Neurological adverse events associated with vaccination

Public tolerance to adverse reactions is minimal. Several reporting systems have been established to monitor adverse events following immunization. The present review summarizes data on neurologic complications following vaccination, and provides evidence that indicates whether they were directly associated with the vaccines. These complications include autism (measles vaccine), multiple sclerosis (hepatitis B vaccine), meningoencephalitis (Japanese encephalitis vaccine), Guillain-Barré syndrome and giant cell arteritis (influenza vaccine), and reactions after exposure to animal rabies vaccine. Seizures and hypotonic/hyporesponsive episodes following pertussis vaccination and potential risks associated with varicella vaccination, as well as vaccine-associated paralytic poliomyelitis following oral poliovirus vaccination, are also described. In addition, claims that complications are caused by adjuvants, preservatives and contaminants [i.e. macrophagic myofasciitis (aluminium), neurotoxicity (thimerosal), and new variant Creutzfeldt-Jakob disease (bovine-derived materials)] are discussed.