Assays for antibodies to varicella-zoster virus

Tiza-Titre increase and enhanced immunity through an adjuvanted, recombinant herpes zoster subunit vaccine in patients with liver cirrhosis and post-liver transplantation: a study protocol for a prospective cohort study

INTRODUCTION

Shingrix, an effective adjuvanted, recombinant herpes zoster vaccine (RZV), has been available since 2018. Immunocompromised patients are known to be predisposed to vaccine failure. In-vitro testing of immunological surrogates of vaccine protection could be instrumental for monitoring vaccination success. So far, no test procedure is available for vaccine responses to RZV that could be used on a routine basis.

METHODS AND ANALYSIS

This is a single-centre, three-arm, parallel, longitudinal cohort study aspiring to recruit a total of 308 patients (103 with a liver cirrhosis Child A/B, 103 after liver transplantation (both ≥50 years), 102 immunocompetent patients (60-70 years)). Blood samples will be taken at seven data collection points to determine varicella zoster virus (VZV) and glycoprotein E (gE)-specific IgG and T cell responses. The primary study outcome is to measure and compare responses after vaccination with RZV depending on the type and degree of immunosuppression using gE-specific antibody detection assays. As a secondary outcome, first, the gE-specific CD4+ T cell response of the three cohorts will be compared and, second, the gE-VZV antibody levels will be compared with the severity of possible vaccination reactions. The tertiary outcome is a potential association between VZV immune responses and clinical protection against shingles.

ETHICS AND DISSEMINATION

Ethical approval was issued on 07/11/2022 by the Ethics Committee Essen, Germany (number 22-10805-BO). Findings will be published in peer-reviewed open-access journals and presented at local, national and international conferences.

TRIAL REGISTRATION NUMBER

German Clinical Trials Registry (number DRKS00030683).

Current Methods for the Detection of Antibodies of Varicella-Zoster Virus: A Review

Infection with the varicella-zoster virus (VZV) causes chickenpox and shingles, which lead to significant morbidity and mortality globally. The detection of serum VZV-specific antibodies is important for the clinical diagnosis and sero-epidemiological research of VZV infection, and for assessing the effect of VZV vaccine immunization. Over recent decades, a variety of methods for VZV antibody detection have been developed. This review summarizes and compares the current methods for detecting VZV antibodies, and discussed future directions for this field.

Varicella-zoster-virus vaccination of immunosuppressed children with inflammatory bowel disease or autoimmune hepatitis: A prospective observational study

BACKGROUND AND AIMS

Children with inflammatory bowel disease (IBD) and autoimmune hepatitis (AIH) receiving immunosuppressive treatment are at risk for severe varicella zoster virus (VZV)-induced disease. This study evaluated vaccination of susceptible patients with stable disease and documented immunoreactivity without interruption of their current immunosuppression (IS).

METHODS

This prospective multicentre observational study used a prevaccination checklist to select patients with low-intensity and high-intensity IS for VZV vaccination. Tolerability and safety after immunization were assessed by questionnaire. The immune response was measured by the VZV-IgG concentration, relative avidity index (RAI), and specific lymphocyte proliferative response.

RESULTS

A total of 29 VZV vaccinations were performed in 17 seronegative patients aged 3-16 years (IBD n = 15, AIH n = 2). Eight patients received high-intensity immunosuppression, another six low-intensity immunosuppression, and three patients interrupted IS before VZV vaccination. All 29 vaccinations were well tolerated; only minor side effects such as fever and abdominal pain, were reported in two patients. One patient experienced a flare of Crohn's disease the day after vaccination. The VZV-IgG-concentration increased significantly (p = 0.018) after vaccination, and a specific lymphocyte response towards VZV in vitro was detected in all tested patients which correlated with the RAI (r = 0.489; p = 0.078).

CONCLUSIONS

VZV vaccination was well tolerated, safe and immunogenic in children receiving ongoing IS due to IBD and AIH. Ensuring immunoreactivity by clinical and laboratory parameters, rather than the type and dosage of IS, is a reasonable approach to decide on live-attenuated virus vaccinations in immunosuppressed children (German clinical trials DRKS00016357).

Sensitivity and specificity of different antibody tests for detecting varicella-zoster virus

INTRODUCTION

Antibody tests for detecting varicella-zoster virus include the fluorescent-antibody-to-membrane-antigen (FAMA) assay, immune adherence hemagglutination assay (IAHA), enzyme immunoassay (EIA), and the glycoprotein-based enzyme-linked immunosorbent assay (gpELISA). Although FAMA and gpELISA are highly sensitive, FAMA is not available commercially. Therefore, this study was performed to compare potential high-sensitivity tests with commercially available tests.

METHODS

Four antibody tests, FAMA, gpELISA, EIA, and IAHA, were performed using sera collected from 32 children aged 7 months-10 years. Using FAMA as a reference, the sensitivity and specificity of gpELISA, EIA, and IAHA were assessed. Subsequently, using gpELISA as a reference, the positive agreement rate of EIA and IAHA was assessed.

RESULTS

On a reference scale with FAMA set at 100%, the sensitivity and specificity of the antibody tests were as follows: gpELISA, 67% and 100%; EIA, 67% and 100%; and IAHA, 47% and 100%, respectively. The positive agreement rates of EIA and IAHA relative to gpELISA were 86% and 64%, respectively.

CONCLUSIONS

gpELISA had a lower positive rate than did FAMA, and showed comparable sensitivity to that of EIA.

Production and Clinical Evaluation of Norwalk GI.1 Virus Lot 001-09NV in Norovirus Vaccine Development

BACKGROUND

Human noroviruses (HuNoV) are the leading cause of gastroenteritis. No vaccine is currently available to prevent norovirus illness or infection. Safe, infectious challenge strains are needed to assess vaccine efficacy in the controlled human infection model (CHIM).

METHODS

A stock of HuNoV strain Norwalk virus ([NV] GI.1) was prepared. Healthy, genetically susceptible adults were inoculated with NV Lot 001-09NV and monitored for infection, gastroenteritis symptoms, and immune responses.

RESULTS

Lot 001-09NV induced gastroenteritis in 9 (56%) and infection in 11 (69%) of 16 genetically susceptible subjects. All infected subjects developed strong immune responses to GI.1 with a 30-fold (geometric mean titer) increase in blocking titers (BT50) and a 161-fold increase in GI.1-specific immunoglobulin (Ig)G titers when compared with baseline. GI.1-specific cellular responses in peripheral blood were observed 9 days postchallenge with an average of 3253 IgA and 1227 IgG antibody-secreting cells per million peripheral blood mononuclear cells.

CONCLUSIONS

GI.1 Lot 001-09NV appears to be similar in virulence to previous passages of NV strain 8fIIa. The safety profile, attack rate, and duration of illness make GI.1 Lot 001-09NV a useful challenge strain for future vaccine studies aimed at establishing immune correlates.

Calibration and Evaluation of Quantitative Antibody Titers for Varicella-Zoster Virus by Use of the BioPlex 2200

Most commercially available enzyme immunoassay-based methods have limited sensitivity to detect antibody responses to varicella-zoster virus (VZV) in vaccinated individuals, who produce lower antibody levels than those with natural infection. However, more sensitive methods are either not commercially available or less amenable to high-throughput testing.

Most commercially available enzyme immunoassay-based methods have limited sensitivity to detect antibody responses to varicella-zoster virus (VZV) in vaccinated individuals, who produce lower antibody levels than those with natural infection. However, more sensitive methods are either not commercially available or less amenable to high-throughput testing. The BioPlex 2200 measles, mumps, rubella, and varicella (MMRV) IgG assay (Bio-Rad Laboratories, Hercules, CA) is an automated high-throughput platform based on the microsphere Luminex technology that measures antibodies against measles, mumps, rubella, and varicella viruses simultaneously. Although it has U.S. Food and Drug Administration approval as a qualitative diagnostic test for measles, mumps, rubella, and varicella virus immunity, in this study, we have validated the assay to produce quantitative titers (off label) against the VaccZyme VZV glycoprotein (VZVgp) low-level IgG kit (The Binding Site Ltd., Birmingham, UK) using the World Health Organization international standard. Here, we show that the BioPlex 2200 MMRV IgG assay has sensitivity superior to that of the Zeus enzyme-linked immunosorbent assay (ELISA) VZV IgG assay (Zeus Diagnostics, Branchburg, NJ). Using receiver operating characteristic (ROC) analysis and adjusting the cutoff levels, we improved the sensitivity of the quantitative BioPlex 2200 MMRV IgG assay to 97.4%, while maintaining 100% specificity.

Herpes zoster involving the abducens and vagus nerves without typical skin rash: A case report and literature review

RATIONALE

Herpes zoster is characterized by unilateral vesicular eruption and it most often affects the trigeminal nerve. We would like to report a rare case of abducens and vagus nerves palsy caused by varicella zoster virus (VZV) without the typical vesicular rash.

PATIENT CONCERNS

A 71-year-old woman presented with diplopia. Three days previously, she had experienced sore throat and hoarseness.

DIAGNOSIS

At presentation, the prism cover test revealed esotropia of 10 prism diopters at primary gaze, and abduction was restricted in the right eye. No vesicular rash was observed on the patient's face, and magnetic resonance imaging of the brain showed no pathology. Flexible fiberoptic laryngoscopy revealed multiple ulcerations on the right side of the larynx-from the epiglottis to the arytenoid. After 1 day of hospitalization, a diffuse skin rash occurred on the patient's trunk, and polymerase chain reaction for VZV DNA was positive at the skin lesion. The patient was diagnosed as having herpes zoster associated with vagus and sixth nerve palsy.

INTERVENTION AND OUTCOMES

She received famciclovir at a dose of 500 mg 3 times daily for 7 days and coadministered methylprednisolone. At the 4-month follow-up, her diplopia and eye movement had resolved completely.

LESSONS

In patients with abducens nerve palsy without typical vesicular lesion, herpes zoster may not be detected early. In that case, systemic examination is very important for diagnosing herpes zoster.

Serological and T Cell Responses After Varicella Zoster Virus Vaccination in HIV-Positive Patients Undergoing Renal Dialysis

Limited data on varicella zoster virus (VZV) vaccine responses are available in HIV-positive adults, especially among those with end-stage renal disease on dialysis or undergoing kidney transplantation (KT). Serological and T cell responses were analyzed using anti-VZV IgG titers, enzyme-linked immunosorbent assay and flow cytometric intracellular cytokine staining (ICS) in two HIV-positive kidney transplant candidates undergoing dialysis and receiving VZV immunization. The results were compared with two HIV-positive and two HIV-negative VZV-seropositive patients (two kidney transplant candidates and two kidney transplant recipients), and with one HIV-negative vaccinee. HIV-positive VZV-susceptible patients received two doses of VZV vaccine 12 weeks apart. No adverse events were reported. Serological data were indicative of immunological response in one patient and corresponded to T cell responses. The second patient showed only a transient increase in anti-VZV IgG titers, but reported positive CD4⁺ T cell responses that were maintained after KT. Positive T cell and serological responses were detected in both HIV-positive and HIV-negative controls. VZV vaccination appeared safe and effective in HIV-positive KT candidates. VZV-specific T cell immunity was detected among transplant candidates and after KT. The assessment of VZV-specific T cell immunity using flow cytometric ICS may be more reliable compared to serology in assessing responses to VZV vaccine in this group.

Negative IgG Varicella Zoster Virus Antibody Status: Immune Responses Pre and Post Re-immunization

INTRODUCTION

Varicella zoster virus (VZV) causes chicken pox and herpes zoster and is a self-limiting disease in healthy children. Vaccination is recommended for children, adolescents, and adults. This study discusses a healthy pediatric patient with negative immunoglobulin (Ig) G VZV antibody (Ab) status after two doses of varicella vaccine and then subsequently re-immunized. Since measurement of serum IgG titers alone may not reflect vaccine protection, we further evaluated cell-mediated and humoral immune responses before and after re-immunization.

METHODS

Blood lymphocyte distributions (CD3+CD4+, CD3+CD8+, CD19+, CD4+CD60+, CD8+CD60+), total serum IgG and IgE levels, and VZV-IgG, IgM, and IgE Ab levels were measured in a healthy girl (14 year-old) pre- and post-VZV re-immunization (weeks 1-8) [flow microfluorimetry, nephelometry, ELISA, enzyme immunoassay (EIA)].

RESULTS

Pre-re-immunization numbers of T cells (CD3+CD4+, CD3+CD8+, CD4+CD60+, CD8+CD60+) and B cells (CD19+) were within normal ranges. After re-immunization, numbers of T cells remained relatively unchanged; however, numbers of CD19+ B cells increased (48%). Total serum IgG was low (757 mg/dl), and total serum IgE was normal (30 IU/ml). Pre-reimmunization, VZV IgG and IgM Ab levels were negative (< 0.90 and < 0.90 antibody index, respectively), and VZV IgE levels were undetectable. After re-immunization, VZV IgG Ab levels were positive (690.70 Ab index), VZV IgM Ab levels were negative (≤ 0.90), and VZV IgE levels remained undetectable.

CONCLUSION

Vaccination with the VZV vaccine may boost IgG but not IgE-specific viral responses and concurrently increase the numbers of CD19+ B cells.

Varicella-zoster virus seroprevalence in children and adolescents in the pre-varicella vaccine era, Germany

Background

In 2004, universal childhood varicella vaccination was introduced in Germany. We aimed to determine the age-specific prevalence of anti-varicella zoster virus (VZV) IgG-antibodies among children in the pre-varicella vaccine era in Germany, to identify factors associated with VZV seropositivity, and to assess the suitability of a commercially available ELISA for VZV seroepidemiological studies by comparing it with an in-house fluorescent antibody to membrane antigen test (FAMA) as the gold standard.

Methods

Serum samples of 13,433 children and adolescents aged 1–17 years included in the population-based German Health Interview and Examination Survey for Children and Adolescents (KiGGS; conducted 2003–2006) were tested for anti-VZV IgG by ELISA. All samples with equivocal ELISA results and a random selection of ELISA-negative and -positive samples were tested by FAMA. Statistical analyses were conducted using a weighting factor adjusting the study population to the total population in Germany. Seroprevalences were calculated as percentages (%) with a 95% confidence interval (CI). Odds ratios (OR) were computed by multivariate logistic regression to determine the association between socio-demographic factors and VZV seropositivity.

Results

The VZV seropositivity rate was 80.3% (95% CI: 79.3–81.3) in varicella-unvaccinated children and adolescents. VZV seropositivity rates differed significantly between age groups up to age 6 years, but not by gender. Of 118 retested serum samples with an equivocal ELISA result, 45.8% were FAMA-positive. The proportion of samples tested as false-negative in by ELISA varied by age group: 2.6% in children aged 1–6 and 9% in children aged 7–17 years. Multivariate analyses showed that age, having older siblings, and early daycare start were associated with seropositivity in preschoolers; migration background reduced the chance of VZV seropositivity in schoolchildren (OR: 0.65; 0.43–0.99) and adolescents (OR: 0.62; 0.4–0.97).

Conclusion

In the pre-varicella vaccine era, most children in Germany contracted varicella by age six. Schoolchildren with a migration background and children without siblings have an increased risk of being VZV seronegative and should be targeted for catch-up vaccination, if they have no history of chickenpox. ELISAs are suitable for use in population-level serosurveys on VZV, but samples with equivocal ELISA results should be retested by FAMA.

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.

Evaluation of a multiplex bead immunoassay for determination of immune status to varicella-zoster virus in medical center students and employees

This study evaluated an enzyme immunoassay, a multiplex bead immunoassay (MBIA), and the anticomplement immunofluorescence (ACIF) test for detecting varicella-zoster virus IgG antibodies in sera from medical center students and employees. The agreement between methods was ≥95%. The MBIA was less sensitive than was the ACIF test, with a negative predictive value of 66.7%.

Evaluation of a commercial glycoprotein enzyme-linked immunosorbent assay for measuring vaccine immunity to varicella

PURPOSE

To evaluate a recently marketed commercial glycoprotein enzyme-linked immunosorbent assay (gpEIA) kit, the VaccZyme™ VZV gpEIA, for measuring the immunity of varicella-vaccinated children.

MATERIALS AND METHODS

We investigated the accuracy and reproducibility of the VaccZyme™ VZV gpEIA kit for the detection of antibodies to VZV. We also examined the sensitivity, specificity, and correlation between antibody titers calculated with gpEIA versus fluorescent antibody to membrane antigen (FAMA) by using sera of 349 children, ranging from 1 to 6 years old.

RESULTS

VaccZyme™ VZV gpEIA gave precise and reproducible intra- and inter-assay results. FAMA and gpEIA titers showed a linear correlation (Pearson correlation coefficient=0.987). The sensitivity and specificity of the VaccZyme™ gpEIA was 31.4% and 100%, respectively, when the guidelines of the gpEIA (<100 mIU/mL) and FAMA 1:4 were adopted as cutoff values. However, the maximum sensitivity and specificity were 88.9% and 95.1%, respectively, with the highest correlation (κ=0.840), if the cutoff values were set with gpEIA at 49.7 mIU/mL and FAMA 1:16.

CONCLUSION

These results demonstrate that the VaccZyme™ VZV gpEIA kit gave precise and reproducible data for measuring antibody titer after varicella vaccination. The results also showed that the antibody titer calculated with the VaccZyme™ gpEIA kit strongly correlated with the FAMA titer. However, cutoff values should be re-optimized for the evaluation of vaccine immunity.

Reduced varicella-zoster-virus (VZV)-specific lymphocytes and IgG antibody avidity in solid organ transplant recipients

BACKGROUND

Varicella-zoster-virus (VZV) infection may cause significant morbidity and mortality in immunocompromised patients. So far, only IgG-anti-VZV antibody concentrations were used to estimate immunity against VZV, but the antibody binding strength (avidity) together with VZV-specific cellular responses have not been evaluated in solid organ transplant (SOT) recipients.

METHODS

Thus, we assessed the humoral and cellular immune responses to two doses of the VZV vaccine (vacc) and wild-type VZV infection (wt) in 23 kidney (KTx) and 19 liver transplant (LTx) recipients including children and adults compared to 48 healthy controls (HC) for measurement of IgG-anti-VZV relative avidity index (RAI) and frequency of VZV-specific peripheral blood mononuclear cells (PBMCs) in vaccinated individuals using an adapted ELISA and IFN-gamma ELISPOT, respectively.

RESULTS

KTx(wt) (median RAI 72.3%) or LTx(wt) (79.2%) and KTx(vacc) (91.0%) or LTx(vacc) (72.5%) showed lower avidities compared to HC(wt) (84.5%) and HC(vacc) (94.0%), respectively, despite equally distributed IgG-anti-VZV concentrations. RAI>60% (high avidity) was detected in all HC, but only in 69.0% of SOT patients. KTx(vacc) (median 64 spot forming units SFU/500,000 PBMCs) and LTx(vacc) (67 SFU) had significantly lower VZV-specific cellular responses compared to HC(vacc) (268 SFU).

CONCLUSIONS

The diminished cellular reactivity to VZV has to be considered in SOT patients receiving immunosuppressive treatments when evaluating immunity against VZV. IgG antibody avidity and VZV-specific cellular responses may serve as additional markers to evaluate immunity against VZV in SOT recipients. The role of wild-type exposures and endogenous VZV re-activation on long-term immunity in SOT patients has to be awaited to establish recommendations for vaccine spacing in these patients, considering immunogenicity and safety aspects.

Serologic analysis of the IgG antibody response in children with varicella zoster virus wild-type infection and vaccination

INTRODUCTION

In contrast to varicella zoster virus (VZV) primary infection, VZV vaccination does not seem to provide lifelong immunity against varicella. Because more people get vaccinated every year, the development of sensitive serological test systems for the detection of protective anti-VZV IgG will become important in the future.

METHODS

We have previously developed a novel VZV line assay based on 5 different recombinant VZV antigens. In this study, we compared this novel assay with a commercially available glycoprotein enzyme immunoassay (RIDASCREEN VZV IgG) in detecting anti-VZV IgG of children with previous varicella infection and VZV vaccination.

RESULTS

One hundred twenty-five children were included in this study, 72 with a history of varicella infection and 53 with VZV vaccination. Both assays detected anti-VZV IgG antibodies in both study groups with similar sensitivities. The VZV line assay revealed striking differences in the anti-VZV IgG composition against the VZV open reading frames, 4, 14 and 49, between both study groups, indicating that wild-type varicella infection causes a more diverse immune response against VZV than does vaccination. The exploitation of these results enabled the discrimination of both study groups with a sensitivity of 0.93 and a specificity of 0.83, indicating that the serologic differentiation of children with previous varicella infection and VZV vaccination might be possible.

CONCLUSION

The VZV line assay enables the detection of anti-VZV IgG with sensitivities comparable to glycoprotein enzyme immunoassays and might be suitable for the serologic discrimination between children with a history of varicella infection and VZV vaccination.

Safety and immunogenicity of a quadrivalent meningococcal polysaccharide diphtheria toxoid conjugate vaccine in infants and toddlers: three multicenter phase III studies

BACKGROUND

Quadrivalent meningococcal conjugate vaccine (Menactra [MenACWY-D]), was licensed in the United States in 2005 to prevent meningococcal disease in adolescents and adults. The license was extended to children aged 2-10 years in 2007 and extended again in 2011 to infants aged 9 months and older based, in part, on results from 3 phase III studies presented herein.

METHODS

The safety and immunogenicity of 2 doses of MenACWY-D was assessed in study-eligible children: dose 1 was administered at 9 months of age and dose 2 was administered 3 months later with or without routine childhood vaccines.

RESULTS

Thirty days after vaccination, protective serum bactericidal assay-human complement titers ≥1:8 for meningococcal serogroups A, C, Y and W-135 were achieved by 86-100% of children receiving 2 doses of MenACWY-D. When MenACWY-D was concomitantly administered with measles, mumps, rubella and varicella or heptavalent pneumococcal conjugate vaccine, 81-98% of participants achieved protective responses (serum bactericidal assay-human complement titers ≥1:8 for all serogroups). All seroprotection rates were >91% when the protective titer was defined as serum bactericidal assay-human complement ≥1:4. MenACWY-D did not interfere with measles, mumps, rubella or varicella vaccine responses (98-100% achieved protective titers). When heptavalent pneumococcal conjugate vaccine was given concomitantly with MenACWY-D, antipneumococcal antibody levels, although decreased, were protective for all serotypes by enzyme-linked immunosorbent assay (98-100% ≥ 0.35 μg/mL) and opsonophagocytic assay (99-100% ≥ 1:8). Adverse events were generally mild and similar across groups. Serious adverse events were uncommon.

CONCLUSIONS

MenACWY-D was safe and immunogenic when given in 2 doses to infants and toddlers; this vaccine can be given with other common childhood immunizations.

Evaluation of three commercial varicella-zoster virus IgG enzyme-linked immunosorbent assays in comparison to the fluorescent-antibody-to-membrane-antigen test

Commercial serologic assays for varicella-zoster virus (VZV), which enable reliable determination of VZV immune status and are amenable to automation, are needed. The present study compares the automated performance of the VZV whole-cell enzyme-linked immunosorbent assay (ELISA) Enzygnost anti-VZV/IgG, the Euroimmun anti-VZV ELISA (IgG) based on highly purified viral proteins, and the VZV glycoprotein (gp)-based Serion ELISA Classic VZV IgG. The fluorescent-antibody-to-membrane-antibody (FAMA) test was used as a reference. A total of 638 serum samples from VZV-negative children, blood donors, varicella vaccinees, and bone marrow transplant recipients were included. The Enzygnost anti-VZV/IgG and the Serion ELISA Classic VZV IgG showed sensitivities of 99.6% and 99.2%, respectively, and the Euroimmun anti-VZV ELISA (IgG) had a significantly lower sensitivity of 90.5%. Specificity was calculated as 100% for both the Euroimmun anti-VZV ELISA (IgG) and for the Enzygnost anti-VZV/IgG, and the Serion ELISA Classic VZV IgG had a significantly lower specificity of 89.4%. Quantitative results of all ELISAs correlated well, but there was a poor quantitative correlation between the ELISAs and FAMA. In conclusion, this study does not show any superiority of a gp- and a protein-based ELISA compared to a whole-cell ELISA for the automated detection of VZV-specific IgG. The automated performance of the Enzygnost anti-VZV/IgG assay correlated best with the FAMA reference assay.

Comparison of a commercial Varicella Zoster glycoprotein IgG enzyme immunoassay with a reference time resolved fluorescence immunoassay (VZV TRFIA) for measuring VZV IgG in sera from pregnant women, sera sent for confirmatory testing and pre and post vOka vaccination sera from healthcare workers

BACKGROUND

Recently, a commercial, standardised VZV IgG glycoprotein EIA, Binding Site VaccZyme™VZV glycoprotein IgG low level EIA (VaccZyme™EIA) has become available. The VaccZyme™EIA is more robust and user friendly than the reference VZV time-resolved fluorescence immunoassay (VZV TRFIA).

OBJECTIVES

To assess the usefulness of the VaccZyme™EIA in the diagnostic laboratory by comparing VZV IgG levels generated by both assays on serum panels representing, non-vaccinated, and vOka vaccinated populations.

STUDY DESIGN

Sera from non-vaccinated individuals were tested; 248 from pregnant women, 117 from various patient groups referred to the Virus Reference Department for confirmatory VZV IgG testing and 102 from healthcare workers enrolled in a study (ROVE) of antibody/IgG response to vOka. From the ROVE study, 282 post vaccination sera were tested; 108 and 101 collected at six weeks post first and second doses of vOka, respectively, and 73 collected at 18 month follow-up.

RESULTS

Sensitivities and specificities (equivocals treated as negatives) of the VaccZyme™EIA for sera from pregnant women were 97.8% (95% CI: [94.6%, 99.4%]) and 96.8% (95% CI: [89.0%, 99.6%]), respectively, and for sera referred for confirmatory testing were 81.2% (95% CI: [71.2%, 88.8%]) and 96.9% (95% CI: [83.8%, 99.9%]), respectively, and for ROVE baseline sera were 54.2% (95% CI: [32.8%, 74.4%]) and 100% (95% CI: [95.4%, 100.0%]), respectively. For the post vOka serum panels sensitivities of the VaccZyme™EIA ranged from 65.3% (95% CI: [50.4%, 78.3%]) to 80.4% (95% CI: [71.1%, 87.8%]). Specificities were all 100%. Correlation with VZV TRFIA was high and agreement varied between the serum panels tested.

CONCLUSIONS

VaccZyme™EIA is recommended for detecting VZV IgG in sera from non-vaccinated populations; however, caution is advised when measuring post vOka VZV IgG levels.

Seroprevalence rate after one dose of varicella vaccine in infants

SUMMARY BACKGROUND

Live, attenuated varicella vaccine has been used since 1988 in Korea. However, varicella is still prevalent among both vaccinated and unvaccinated individuals, despite a relatively high level of immunization rate up to 80%. A recent report has demonstrated approximately 20% of primary vaccine failure rate after one dose of varicella vaccine using the fluorescent antibody to membrane antigen (FAMA) assay.

METHODS

The seroprevalence rate was determined using the FAMA and ELISA assays in 67 Korean infants following one dose of varicella vaccine. Positive fluorescence at a serum dilution of 1:4 or greater was considered as seropositive.

RESULTS

The median age at vaccination was 12 months and the post-immunization sera were obtained on average 6.3 months (range 6 weeks-12 months) after vaccination. Among the 67 vaccinated infants, 56 (83.6%) were seropositive by FAMA assay while 30 (44.8%) were seropositive by ELISA. The geometric mean titers (GMTs) of the seropositive vaccinated infants (n = 56) were significantly lower than the GMTs of 9 individuals with a history of varicella (1:17.0 vs. 1:74.7, P = 0.001). Although there were no significant differences in seropositive rates according to intervals, there was a decreasing trend in the GMTs over time among the 56 seropositive recipients (r(2) = 0.154, P < 0.001).

CONCLUSIONS

These data can be useful for optimizing the immunization strategy against varicella and should be confirmed by a prospective study including a large number of immunized infants.

Varicella vaccination in pediatric kidney and liver transplantation

Reports about efficacy and safety of live-virus attenuated vaccines in patients before and after transplantation are mainly based on small patient numbers, making general recommendations for this patient population difficult. Children and adults as well as their close relatives and contact persons should be preferably immune to VZV before solid organ transplantation to avoid VZV-associated complications, thus making VZV vaccination necessary in susceptible individuals. The following literature review focused on efficacy and safety of VZV vaccination in pediatric kidney and liver transplant recipients. Review of literature also revealed that in all pediatric transplant candidates, humoral and cellular immunity against VZV should be consistently monitored to assess waning immunity under immunosuppressive treatment. This approach is desirable to estimate the risk of severe varicella disease after exposure in these patients.

Viruses

Viral infections are an important and often unrecognized component of disease in immunocompromised patients. The diagnosis and management of viral infections have expanded largely because of new quantitative molecular diagnostic assays. Well-recognized pathogens such as herpes simplex virus (HSV), cytomegalovirus (CMV), and respiratory viruses have been joined by newly recognized pathogens such as BK virus, human herpesvirus-6 (HHV-6), and human metapneumovirus in this highly susceptible patient population. The role of Epstein-Barr virus (EBV) and Human herpesvirus-8 (HHV-8) in lymphoproliferative diseases also continue to be clarified. As a result, the management of viral infections in patients with hematologic malignancies continues to be a growing challenge for the clinician.

Comparison of fifteen commercial assays for detecting Varicella Zoster virus IgG with reference to a time resolved fluorescence immunoassay (TRFIA) and the performance of two commercial assays for screening sera from immunocompromised individuals

The performance of fifteen, commercially available, VZV IgG assays and an "in house" indirect immunofluorescence (IF) assay has been compared to a reference VZV IgG time resolved immunofluorescence assay (VZV TRFIA). A panel of 273 VZV TRFIA IgG positive serum samples and 136 VZV TRFIA IgG susceptible sera, collected from a number of UK hospitals was used. Irrespective of the interpretation of equivocal results the most sensitive assays were Dade Behring EIA (97.4%), "in house" IF (95.2%), Human EIA (92.3%) and Becton Dickinson latex agglutination (94.1%). The least sensitive assays were Virion EIA (69.6%), Diesse EIA (68.9%) and Diasys EIA (68.5%). The least sensitive (<70%) assays all had >99.0% specificity whereas the most sensitive assays had lower specificities; for example, Dade Behring EIA had a specificity of 69.9% when equivocals were treated as VZV IgG negative. For some assays e.g. Dade Behring EIA there were major discrepancies between our findings and those reported by the manufacturer which may reflect the constitution of the panel(s) of sera used for evaluation or the reference method adopted or the choice of cut-off criteria (particularly relevant to our findings for the Behring EIA). Care must be taken to choose an assay with high specificity in order to accurately assess the need for vaccination or immunoprophylaxis; however, high sensitivity is preferable to prevent inappropriate and expensive treatment.

Novel recombinant ELISA assays for determination of type-specific IgG antibodies against HSV-1 and HSV-2

The two novel Novagnost enzyme-linked immunosorbent assays (ELISA, Dade Behring) based on recombinant viral glycoprotein G were evaluated for determination of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) IgG. ELISA and immunoblot procedures approved by the US Food and Drug Administration served as the reference for selecting different serum panels to be tested. The sensitivity and specificity of the novel assay for HSV-1 IgG were 93.1-98.0% and 99.3-100%, respectively, while the sensitivity and specificity of the novel assay for HSV-2 IgG were 100% and 94.6-97.6%, respectively. Using Kappa statistics, the Kappa indices were computed at 0.93-0.98 for the HSV-1 assays and 0.92-0.96 for the HSV-2 assays suggesting an almost perfect agreement between the novel ELISAs and the reference tests. In conclusion, the novel immunoassays for determination of HSV-1 or HSV-2 IgG can be recommended for the reliable type-specific diagnosis of HSV infections.

Reliability of information on varicella history in preschool children

OBJECTIVE

To verify how reliable is the information provided by parents about the history of varicella in their children.

METHODS

204 parents of previously healthy children attending two municipal day-care centers of São Paulo city were interviewed between August 2003 and September 2005. A standardized form was filled out with information regarding age, sex, history of varicella and other diseases, drug use and antecedent of immunization, After medical history, physical examination and checking of immunization records, 5 ml of blood were collected for ELISA (in house) varicella test. Exclusion criteria were: age less than 1 year or more than 60 months, previous immunization against chickenpox, presence of co-morbidities or recent use of immunosuppressive drugs. Data were filed in a data bank using the Excel 2003 Microsoft Office Program and stored in a PC computer. The exact Fisher test was employed to calculate sensibility, specificity, positive and negative predictive values of history of varicella informed by children's parents.

RESULTS

The age of the children varied from 12 to 54 months (median, 26 months; 49 (24%) children had positive history of varicella, 155 (76%) a negative or doubtful history. The predictive positive and negative values of the information were 90% and 93%, respectively (p = 0.0001).

CONCLUSIONS

The degree of reliability of information about history of varicella informed by parents of children attending day care centers was high and useful to establish recommendations on varicella blocking immunization in day-care centers.

The optimization and validation of the glycoprotein ELISA assay for quantitative varicella-zoster virus (VZV) antibody detection

Varicella is a highly contagious viral disease found throughout the world. A live-attenuated Varicella-Zoster virus (VZV) vaccine (Oka/Merck strain), VARIVAXtrade mark, was licensed in the United States (US) in 1995 and was made a part of the US recommended childhood vaccination schedule in 1996. The immune response to VZV-containing vaccines has been measured using an enzyme-linked immunosorbent assay (ELISA) to detect antibodies to glycoproteins from VZV. A correlate for protective immunity has been established between anti-VZV glycoprotein antibody levels and protection against breakthrough varicella in children, and this correlate is used as the primary immunogenicity endpoint in clinical trials with VZV-containing vaccines. The performance of the "first generation" validated version of the assay was recently reevaluated in order to identify areas for improvement. Specific format and reagent changes were implemented, with the goal of improving assay consistency by maintaining tighter control over assay processes and reagents. An extensive validation of the "second generation" gpELISA was undertaken in order to characterize the updated assay. In this article, we describe the gpELISA method, detail the procedures used to evaluate assay performance, and present the operating characteristics of the second generation gpELISA.

Serological detection of varicella-zoster virus-specific immunoglobulin G by an enzyme-linked immunosorbent assay using glycoprotein antigen

Since the introduction of varicella vaccination in several countries, there has been an urgent need for commercially available test procedures that allow highly sensitive and specific quantitative determination of the varicella-zoster virus (VZV)-specific immune status, including immunity postimmunization. This study compared the performance of two enzyme-linked immunosorbent assays (ELISAs) for the sensitive and specific determination of VZV-specific immunoglobulin G (IgG) in seronegative and latently infected persons, as well as in vaccinees. One ELISA is based on the detection of antibody to VZV-specific envelope glycoproteins (gp), and the other comprises the whole antigen extract prepared from VZV-infected cells. A modified standard fluorescent-antibody-to-membrane-antigen (FAMA) assay was used as a reference. An excellent sensitivity (100%) in relation to FAMA was demonstrated for the gpELISA (Virion\Serion), while the non-gpELISA (Dade Behring) had a lower sensitivity (83%) when sera from latently infected persons were tested. After postvaccinal immunity was measured, a sensitivity of 87% was achieved with gpELISA, whereas the ELISA incorporating antigen extract of VZV-infected cells had a sensitivity of 78%. Excellent specificity (100%) was calculated for both the gpELISA and the non-gpELISA. In conclusion, SERION ELISA classic VZV IgG is useful for the sensitive and specific quantitative determination of VZV immune status after natural infection. The test can also be recommended for measuring antibody response after varicella vaccination, particularly after the cutoff value was optimized.

Varicella

Varicella-zoster virus, a herpesvirus, causes varicella (chickenpox) and, after endogenous reactivation, herpes zoster (shingles). Varicella, which is recognised by a characteristic vesicular rash, arises mainly in young children, although older individuals can be affected. In immunocompetent patients, symptoms are usually mild to moderate, but an uncomplicated severe case can have more than 1000 lesions and severe constitutional symptoms. Serious complications--including central nervous system involvement, pneumonia, secondary bacterial infections, and death--are sometimes seen. Varicella can be prevented by vaccination. Vaccine is about 80-85% effective against all disease and highly (more than 95%) effective in prevention of severe disease. In the USA, a routine childhood immunisation programme has reduced disease incidence, complications, hospital admissions, and deaths in children and in the general population, indicating strong herd immunity. Similar immunisation programmes have been adopted by some other countries, including Uruguay, Germany, Taiwan, Canada, and Australia, and are expected to be implemented more widely in future.

Performance of a time-resolved fluorescence immunoassay for measuring varicella-zoster virus immunoglobulin G levels in adults and comparison with commercial enzyme immunoassays and Merck glycoprotein enzyme immunoassay

Highly sensitive and specific, quantitative assays are needed to detect varicella-zoster virus (VZV) immunoglobulin G in human sera, particularly for determining immune status and response following vaccination. A time-resolved fluorescence immunoassay (TRFIA) has been developed, and its performance was compared to that of two commercial enzyme immunoassays (EIAs) and Merck glycoprotein EIA (gpEIA). The TRFIA had equivalent sensitivity (97.8%) and high specificity (93.5%) in relation to gpEIA. A commercial (Behring) EIA compared favorably with TRFIA in terms of sensitivity (98.4%) but had lower specificity (80.7%). Another commercial EIA (Diamedix) had high specificity (97.1%) but low sensitivity (76.4%) compared to TRFIA if equivocal test results were treated as negative for VZV antibody. A novel feature of the TRFIA was that the cutoff was generated using population mixture modeling and was expressed in mIU/ml, as the assay was calibrated using the British standard VZV antibody.

Seroepidemiology of varicella-zoster virus infection in a cosmopolitan city (Erzurum) in the eastern Turkey

OBJECTIVE

The aim of the study was to determine VZV seroprevalence under age 30 and to identify the relationship of VZV seroprevalence and several sociodemographic characteristics of the study subjects. The results were presented in order to design a strategy for vaccination against varicella-zoster virus (VZV).

MATERIAL AND METHOD

It was planned to include a total of 568 subjects. The sampling method of 30 clusters recommended for field studies was used for selecting subjects of a predetermined number in the rural and urban areas in eastern Turkey. ELISA method was used to examine the blood samples for VZV seropositivity. Age, gender, place of living, educational level, family size and socioeconomic status was investigated in the study subjects.

RESULTS

Positive VZV seroprevalence was detected in 78% of 559 subjects. Seroprevalence increased with age. Seroprevalence was 16.67% at the age of 1 year, subsequently increased to 57.58% at the age of 4 years, 70% at the age of 7 years, 92.31% at the age of 10 years and then remained 86.78-96.36% in subjects over the age of 10 years. No association was found between sociodemographic variables studied and prevalence levels of antibodies except for educational level in the 0-14 year group.

CONCLUSION

These results suggest that the majority of VZV infections occur during the early childhood; the best option to reduce the circulation of wild type VZV in the population would be the immunization of young children. VZV vaccine should be introduced into the routine childhood vaccination programme in Turkey.

Loss of antibodies to measles and varicella following solid organ transplantation in children

The objective of this study was to determine if loss of antibodies to measles and to varicella occurs in pediatric solid organ transplant recipients. Antibodies were measured in eight hepatic, four cardiac, and six renal transplant patients who had antibodies to measles prior to transplantation, and in six hepatic, five cardiac, and seven renal transplant patients who had antibodies to varicella prior to transplantation. Within 6 months of the transplant, loss of antibodies occurred in four of 18 patients who were seropositive for measles prior to transplantation (22.2%) and in two of 18 patients who were seropositive for varicella prior to transplantation (11.1%). In conclusion, serology for measles and varicella should be considered annually following solid organ transplantation so that appropriate advice can be given to patients who have seroreverted.

Varicella zoster virus antibody titers after intravenous zoster immune globulin in neonates, and the safety of this preparation

AIMS

1) To assess the safety of intravenous varicella zoster virus hyperimmune globulin G (IV-VZVIG) in neonates; 2) measure varicella zoster virus-specific IgG antibody (VZVIG) changes in newborn IV-VZVIG recipients.

METHODS

Eighteen neonatal intensive care unit (NICU) neonates with varicella exposure were given 1 ml/kg (43 International Units (IU)/kg) Varitect IV-VZVIG. Serum VZVIG titers were assayed in neonatal recipients 0, 1, 7, 14, 21, 28, and 35 d after IV-VZVIG. Also, serum samples for VZV-IgM antibody determinations were obtained at 4 wk post-infusion.

RESULTS

No varicella developed in the 18 infants. Infusion of 1 ml/kg (43 IU/kg) IV-VZVIG was generally safe. The IV-VZVIG dose resulted in seroconversion of a non-immune newborn. Five infants had low basal VZVIG titers, and two of them had a 0.6-log10 increase at 24 h post-infusion. Neonatal VZVIG titers (mean+/-SEM in log(10)) before IV-VZVIG and after by 1, 7, 14, 21, 28, and 35 d were 2.22+/-0.15, 2.17+/-0.17, 2.02+/-0.12, 0.87+/-0.2, 1.09+/-0.19, 2.33+/-0.07, and 2.16+/-0.1, respectively.

CONCLUSIONS

One ml/kg (43 IU/kg) IV-VZVIG was generally safe. Our neonatal mean VZV-immune status did not significantly increase after the 1 ml/kg (43 IU/kg) IV-VZVIG dose, although no varicella developed and it caused a VZV-specific seroconversion.

A simple and cheaper in house varicella zoster virus antibody indirect ELISA

We have developed a cheaper an simple in house indirect ELISA that uses the live attenuated VZV vaccine as a coating antigen. The alternative ELISA had an agreement of 94% when compared with a commercial VZV ELISA kit. Moreover, our ELISA proved to be more reliable than the kit when assessing true negative samples. By adding a standard serum, we were able to produce results in international units per millilitre. Also, the addition of an extra step with 8M urea allowed the assessment of VZV IgG avidity without excessive costs. The cost per sample to test VZV IgG was 2.7 times cheaper with our ELISA, allowing the testing of many samples without the burden of production of VZV antigen in the laboratory.

Immunofluorescence test for sensitive detection of varicella-zoster virus-specific IgG: an alternative to fluorescent antibody to membrane antigen test

A highly sensitive indirect fluorescence antibody test (IFAT) has been developed on the basis of varicella-zoster virus (VZV)-infected human lung carcinoma (A549) cells and evaluated for the determination of immunity to VZV. Different serum panels with negative, low, moderate or high anti-VZV IgG levels detected by the fluorescent antibody to membrane antigen (FAMA) assay were investigated. As a result, the sensitivity and the specificity of IFAT were 100% compared to FAMA test. In anti-VZV IgG-positive sera, a significant correlation between the results of FAMA procedure and IFAT could be shown. However, there were considerably higher antibody titers by the IFAT than by FAMA. Whereas the FAMA test had a detection limit of 250 mIU/ml anti-VZV IgG, the limit of detection of IFAT was 50 mIU/ml. In conclusion, the IFAT using VZV-infected A549 cells as antigen allows a highly sensitive, specific, and rapid detection of anti-VZV IgG class antibodies. This simple technique can replace the labor-intensive FAMA procedure for laboratory determination of immunity to VZV.

Ten year follow-up of healthy children who received one or two injections of varicella vaccine

BACKGROUND

The rate of varicella and persistence of varicella antibody after a one dose vs. a two dose regimen of varicella virus vaccine live Oka/Merck (VARIVAX; Merck & Co., Inc., West Point, PA) in approximately 2000 children were compared during a 9- to 10-year follow-up period.

METHODS

Children 12 months to 12 years of age with a negative history of varicella were randomized in late 1991 to early 1993 to receive either one or two injections of varicella vaccine given 3 months apart. Subjects were actively followed for varicella, any varicella-like illness or zoster and any exposures to varicella or zoster on a yearly basis for 10 years after vaccination. Persistence of varicella antibody was measured yearly for 9 years.

RESULTS

Most cases of varicella reported in recipients of one or two injections of vaccine were mild. The risk of developing varicella >42 days postvaccination during the 10-year observation period was 3.3-fold lower (P < 0.001) in children who received two injections than in those who received one injection (2.2% vs. 7.3%, respectively). The estimated vaccine efficacy for the 10-year observation period was 94.4% for one injection and 98.3% for two injections (P < 0.001). Measurable serum antibody persisted for 9 years in all subjects.

CONCLUSIONS

Administration of either one or two injections of varicella vaccine to healthy children results in long term protection against most varicella disease. The two dose regimen was significantly more effective than a single injection.

Inverse relationship between six week postvaccination varicella antibody response to vaccine and likelihood of long term breakthrough infection

BACKGROUND

We used the large clinical database that supported the development of Oka/ Merck varicella vaccine to study the relationship between the primary varicella antibody response, as determined by gpELISA, an enzyme-linked immunosorbent assay that detects antibodies to varicella-zoster virus (VZV) glycoprotein, and the subsequent risk of postvaccination breakthrough varicella.

METHODS

We vaccinated 1,164 healthy children with a single dose of varicella vaccine containing 2900 to 9000 plaque-forming units/dose. The primary immune response to vaccination was determined by gpELISA 6 weeks after vaccination. Subjects were followed annually for 7 years to ascertain cases of breakthrough varicella.

RESULTS

The estimated vaccine efficacy among children with a 6-week postvaccination antibody titer of > or = 5 gpELISA units was 95.5% (95% confidence interval, 94.2%, 96.8%) compared with 83.5% (95% confidence interval, 76.9%, 89.5%) for subjects with a titer of <5 gpELISA units. Children with a 6-week postvaccination antibody titer of <5 gpELISA units were 3.5 times more likely than those with a titer of > or = 5 gpELISA units to develop breakthrough varicella.

CONCLUSIONS

We identified a 6-week postvaccination antibody titer of > or = 5 gpELISA units as an approximate correlate of protection. In addition we established an accelerated failure time model based on log normal hazard that predicted varicella breakthrough rates based on the distribution of 6-week postvaccination varicella antibody titers.

Neonatal varicella

Neonatal varicella is mostly caused by maternal chickenpox acquired during the last 3 weeks of pregnancy. Transplacentally transmitted infections occur in the first 10 to 12 days of life, whereas chickenpox after that time is most likely acquired by postnatal infection. If the mother develops rash between days 4 and 5 antepartum to day 2 postpartum, generalized neonatal varicella leading to death occurs in up to 20% of affected cases. Neonatal chickenpox within the first 4 days after birth has usually been found to be mild. A fatal outcome has been reported in 23% of cases if neonatal chickenpox occurs between 5 and 10 to 12 days of age. Serological methods have been widely used to confirm clinical diagnosis. For rapid virological diagnostics, amplification of viral DNA in skin swabs by polymerase chain reaction is the method of choice. To prevent severe neonatal chickenpox, passive immunization is indicated. If varicella occurs, acyclovir treatment has to be administered promptly.

Seroprevalence of varicella-zoster virus in the German population

The present study was conducted to generate data on the epidemiology of varicella-zoster virus (VZV) infections in Germany as a basis for health economic evaluations of varicella vaccination strategies. The survey was designed as a cross-sectional, age-stratified study of the VZV seroprevalence in the German population. The status of immunity of 4602 individuals a aged 0 to >70 years was investigated by means of an indirect enzyme immunoassay and the fluorescent antibody to membrane assay. After waning of maternal antibodies over the period of 6-9 months seropositivity rates remained low by the end of the 1st year of life. By the age of 4-5 years 62.5% (95% CI; 56.0-68.5) of the pre-school children had already been infected with VZV and at the age of 10-11 years 94.2% (95% CI; 91.0-96.0) of children were positive for anti-VZV antibodies. Among the age-group of >40 years old, only few individuals were susceptible for VZV. The median antibody levels to VZV did not significantly decline with increasing age. In comparison with figures of previous studies the age-specific seroprevalence data presented here do not provide evidence for an upward shift in the age distribution of varicella in Germany. Since the majority of VZV infections occurs during the early childhood, the best option to reduce the circulation of wild-type VZV in the population would be the immunization of young children.

Serotesting versus presumptive varicella vaccination of adolescents with a negative or uncertain history of chickenpox

OBJECTIVE

To review the current practice of adolescent health care providers when an adolescent reports a negative or uncertain history of chickenpox in order to provide information for future practice.

METHODS

Retrospective chart review of a sample of patients seen in a hospital-based adolescent primary care clinic between 1996 and 1999.

RESULTS

Among adolescents who reported a positive history of chickenpox (190 patients, aged 15 +/- 1 years), varicella occurred before age 5 years in 30%, between 5 and 10 years in 56%, and at older than age 10 years in 14% of the patients. When adolescents reported a negative or uncertain history of varicella (55 patients, aged 15 +/- 1 years), serotesting was ordered for the majority (73%) of cases, while only 16% were presumptively vaccinated with varicella vaccine. In six patients no intervention was noted in the charts, and these patients were contacted. In 80% of the patients who were serotested, varicella IgG titers of > or = 1:32 indicated a previous unnoticed infection and lifelong immunity to varicella. In only 20% of the patients sera were negative for varicella IgG titer, requiring varicella vaccination. There was no statistical difference between the number of siblings of patients with a positive serologic test (3 +/- 1) and the number of siblings of seronegative patients (2 +/- 1, p = 0.41). Seven of the eight seronegative patients consented to varicella vaccination and were vaccinated within 10 months of serotesting.

CONCLUSIONS

These data support the practice of serotesting for a previously unnoticed varicella infection rather than presumptive vaccination in the adolescent age group. A follow-up vaccination of seronegative adolescents should be scheduled as close to serotesting as possible.

The postmarketing safety profile of varicella vaccine

The postmarketing safety profile of varicella vaccine was evaluated by analyzing selected adverse experience reports temporally associated with the administration of the vaccine. There were 7963 reports voluntarily submitted to Merck for an overall reporting rate of 5.0 per 10000 doses of vaccine distributed. A varicella zoster virus (VZV) identification program detected the presence of the Oka vaccine strain in three individuals with an immune deficiency - two with pneumonia and one with hepatitis - and in three instances of secondary transmission from vaccinees with vesicular lesions to susceptible household contacts. The Oka vaccine strain was present in 23 patients and wild-type VZV was present in 15 patients with herpes zoster. Vesicular rashes that occurred within 2 weeks of vaccination were more likely to contain the presence of wild-type VZV, while vesicular rashes that occurred more than 2 weeks post-vaccination were more likely to contain the Oka vaccine strain. Eleven patients were hospitalized with complications of breakthrough varicella infection.

Occupational risk of infection by varicella zoster virus in Belgian healthcare workers: a seroprevalence study

OBJECTIVES

To assess the prevalence of varicella zoster virus (VZV) antibodies in Flemish (Belgian) healthcare workers, to investigate the association between seronegativity and selected variables, and to assess the reliability of recall about disease as a predictor of immunity.

METHODS

A seroprevalence study of VZV antibodies (IgG) was conducted among a systematic sample of 4923 employees in various professional groups, employed in 22 hospitals in Flanders and Brussels (Belgium). Information about sex, age, department, job, and years of employment, the country of origin, and history of varicella was obtained. The presence of VZV antibodies was investigated with the enzyme linked immunosorbent assay (ELISA), Enzygnost anti VZV / IgG (Dade Behring, Marburg, Germany). Statistical analysis was performed by calculating prevalences and prevalence ratios (PRs) and their 95% confidence intervals (95% CIs). Sensitivity, specificity, and positive and negative predictive values (PPV and NPV) of the recalled history were determined.

RESULTS

The prevalence of VZV seropositivity in Flemish healthcare workers was 98.5% (95% CI 98.1 to 98.8). Seronegativity was significantly associated with age and job, increasing with both older and younger age. The prevalence of seronegative workers was significantly less in nursing staff than non-nursing staff. There was no significant difference for sex and years of employment. The PPV and NPV of recalled history were 98.9% and 3.4%. Sensitivity and specificity were 83% and 38.9%.

CONCLUSION

The prevalence of VZV seropositivity was very high in this sample of Flemish healthcare workers. Because of this low overall susceptibility, VZV infection seems not to be an important occupational risk among healthcare workers in Flanders. The increasing seronegativity above the age of 45 is possibly due to a loss of detectable antibodies. A positive history of varicella was a good predictor of immunity, but a negative history had no value as a predictor of susceptibility in adults.

Varicella zoster viral disease

Herpes zoster is cause of considerable morbidity, especially among elderly patients, with a suggestion of a slight increase in incidence among female patients. Substantial research on the biology of the varicella zoster virus has led to advances in our knowledge of the pathophysiology of the disease along with more successful therapy for the acute episodes of herpes zoster. Ophthalmic zoster is more common than zoster in other cranial nerves and is associated with pronounced suffering. This article reviews the epidemiology, biology, and latency of herpes zoster, discusses the pathophysiology of the disease, and describes treatment options with antivirals and corticosteroids. The pathophysiology and treatment options for postherpetic neuralgia are also addressed. The varicella vaccine is now available, and initial results suggest that this may lessen the effect of herpes zoster in the future.

Breakthrough varicella infection in a healthcare worker despite immunity after varicella vaccination

Although varicella vaccination is recommended for varicella-susceptible healthcare workers (HCWs), breakthrough infection after vaccination is not unusual, especially following household exposures. We report breakthrough varicella in a vaccinated HCW and review the data on breakthrough infection and concerns for the healthcare setting.

Seroconversion rates in healthcare workers using a latex agglutination assay after varicella virus vaccination

OBJECTIVES

To determine the seroconversion rate after varicella immunization of healthcare workers (HCWs) and the effect of seroconversion rate on current cost-based recommendations for universal vaccination.

METHODS

A voluntary vaccination program for HCWs was performed at a tertiary-care cancer center in New York City. A commercial latex agglutination assay was used to test postvaccination antibody response. Costs for vaccination and postvaccination serological testing were compared to potential costs of postexposure employee furloughs.

RESULTS

Of 263 seronegative HCWs, 96 (36.5%) began the vaccine program. Thirty-nine HCWs received only one dose of vaccine. Seven returned for follow-up antibody testing, of whom 4 were seropositive. Of the 57 HCWs who received two doses, 38 returned for follow-up serology. Thirty-one (81.6%) HCWs were seropositive for varicella-zoster virus antibodies, and seven HCWs (18.4%) remained seronegative. Total cost of vaccination for all 263 seronegative HCWs was estimated and compared to the cost of varicella-related furloughs at our institution.

CONCLUSIONS

We found a considerably lower rate of vaccine-induced seroconversion at our hospital compared to that of the published literature. Despite this finding, universal varicella vaccination remained an extremely cost-effective alternative to the furloughing of exposed, seronegative HCWs. Projected hospital savings exceeded $53,000 in the first year after vaccination alone.

Seroprevalence of varicella antibodies among new house officers

STUDY OBJECTIVE

Varicella, an illness common to children, can occur in nonimmune adults, often causing serious morbidity and mortality. House officers without protective titers to varicella are at risk of contracting the disease and may spread it to the patients they serve. They are also subject to significant losses in work time and wages. Accordingly, in August 1996, the Centers for Disease Control and Prevention recommended vaccinating nonimmune health care providers with the varicella vaccine. We also sought to document the seroprevalence of varicella antibodies among new house officers and to determine the association of self-reported history of infection with varicella antibody levels.

METHODS

This study was conducted at a university-affiliated teaching hospital. Serology testing was performed on house officers beginning their residencies in July 1997. Subjects provided information regarding demographics, medical history, previous varicella exposure, and previous administration of varicella vaccine. Serum was tested using the FIAX test kit, (Biowhitaker, Walkersville, MD).

RESULTS

One hundred fifty-four house officers participated. The mean age was 30 (range, 24 to 50+/-SD 5.5 years). History of varicella infection was given by 119 (77%) of the 154 subjects, whereas 15 (10%) reported no history of infection, and 20 (13%) were uncertain. Ten (7%) of the participants had received varicella vaccine previously. Overall, 6 (4%) had nonprotective titers to varicella. Of the 119 house officers who reported a history of varicella, only 2 (1.7%) had nonprotective titers, and 4 (27%) who reported no history of varicella infection had nonprotective titers. Of the 10 house officers who had previously received varicella vaccine, 1 (10%) had nonprotective titers.

CONCLUSION

Although most house officers had protective titers, a reported history of varicella or the administration of varicella vaccine did not assure the presence of protective titers. House officers should be tested for varicella immunity regardless of a history of previous infection or the administration of varicella vaccine.