An intradermal skin test for determination of immunity to varicella.
(49/662)
AIMS: To evaluate the usefulness of a diluted, inactivated solution of attenuated varicella vaccine in predicting susceptibility to varicella and its correlation with specific antibody titre to varicella. METHODS: In a prospective blinded study, 63 healthy subjects (aged 2-43 years) were studied. Skin test solution was prepared from vials of OKA strain virus which was inactivated by exposure of the vials to room temperature for 10 days; solution was diluted at 1/50 with normal saline and kept at 4 degrees C until used for skin testing. The material was injected intradermally. Serum samples were drawn prior to skin testing and kept at -70 degrees C until analysis for antibody assay by the indirect fluorescent antibody (IFA) method. RESULTS: Forty three patients were IFA antibody positive; 41 of them reacted to the skin test. One of the 20 IFA negative patients reacted to the skin test. Sixteen patients had two serological tests performed, one month apart. Four out of these 16 patients tested negative with the skin test. All four had negative serology on both samples. Six of the 12 IFA positive patients showed a boost in the antibody titre one month after application of the skin test. The specificity and sensitivity of the skin test compared to the IFA assay were both 95%, and the positive and negative predictive values were 97% and 90% respectively. CONCLUSIONS: Results suggest that a varicella skin test prepared using this simple and relatively cheap method is a safe, sensitive, and specific tool by which to assess immunity to varicella. (+info)
Varicella zoster virus. Recent advances in management.
(50/662)
OBJECTIVE: To provide an update on strategies for managing varicella zoster virus (VZV) and for preventing and treating established postherpetic neuralgia (PHN). QUALITY OF EVIDENCE: Treatment guidelines are based on randomized clinical trials. Recommendations concerning other aspects of VZV management (e.g., vaccination) are based mainly on expert opinion. MAIN MESSAGE: Varicella and herpes zoster caused by VZV can give rise to serious morbidity and mortality and should be treated. For preventing chickenpox, safe and effective immunization is widely recommended. Treating varicella-exposed seronegative pregnant women requires special attention because the virus can harm expectant mothers, fetuses, and newborns. The antiviral drugs, acyclovir, valacyclovir, and famciclovir, have been approved for treating herpes zoster and have a role in reducing the duration of PHN. Established PHN can be managed with analgesics, tricyclic antidepressants, and other agents. CONCLUSION: Vaccination and antiviral and other systemic agents can substantially reduce the morbidity associated with VZV infection. (+info)
Neonatal varicella.
(51/662)
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. (+info)
Phylogenetic analysis of varicella-zoster virus: evidence of intercontinental spread of genotypes and recombination.
(52/662)
A heteroduplex mobility assay was used to identify variants of varicella-zoster virus circulating in the United Kingdom and elsewhere. Within the United Kingdom, 58 segregating sites were found out of the 23,266 examined (0.25%), and nucleotide diversity was estimated to be 0.00063. These are an order of magnitude smaller than comparable estimates from herpes simplex virus type 1. Sixteen substitutions were nonsynonymous, the majority of which were clustered within surface-expressed proteins. Extensive genetic correlation between widely spaced sites indicated that recombination has been rare. Phylogenetic analysis of varicella-zoster viruses from four continents distinguished at least three major genetic clades. Most geographical regions contained only one of these three strains, apart from the United Kingdom and Brazil, where two or more strains were found. There was minimal genetic differentiation (one or fewer substitutions in 1,895 bases surveyed) between the samples collected from Africa (Guinea Bissau, Zambia) and the Indian subcontinent (Bangladesh, South India), suggesting recent rapid spread and/or low mutation rates. The geographic pattern of strain distribution would favor a major influence of the former. The genetic uniformity of most virus populations makes recombination difficult to detect. However, at least one probable recombinant between two of the major strains was found among the samples originating from Brazil, where mixtures of genotypes co-occur. (+info)
Simultaneous administration of varicella vaccine and other recommended childhood vaccines--United States, 1995-1999.
(53/662)
Live attenuated varicella vaccine (Var) is recommended in the United States for children aged 12-18 months and for susceptible older children, adolescents, and adults. The Advisory Committee on Immunization Practices recommends that Var be administered either simultaneously with measles-mumps-rubella (MMR) vaccine or separately by > or =30 days. This report summarizes an evaluation of these recommendations, which found that a decrease in Var effectiveness occurred when Var was administered <30 days after MMR; therefore, as currently recommended, physicians should administer Var simultaneously with MMR or wait at least 30 days if the vaccines are administered separately. (+info)
Varicella transmission in two samples of children with different social behaviour in the State of Sao Paulo, Brazil.
(54/662)
In order to establish the differences in transmission pattern of varicella-zoster virus (VZV), a comparative seroepidemiological study was carried out in two different children samples. Children aged 1-11 years, were randomly selected from state schools of Sao Paulo city, Brazil. Individuals aged 1-15 years were sampled by cluster from Caieiras city. Children aged 3 years or under from Caieiras were not attending school, while those from Sao Paulo were attending all-day nurseries or kindergarten. The presence of antibodies to VZV was analysed by ELISA technique. The force of infection and contact rate were determined by mathematical techniques. The average age of first infection was 2.87 +/- 0.14 years and 4.07 +/- 0.47 years for Sao Paulo and Caieiras, respectively. The average force of infection estimated was 0.29 year(-1) for Sao Paulo and was 0.26 year(-1) for Caieiras. The proportion of seropositivity and the force of infection were higher in Sao Paulo school children up to 3 years of age compared with Caieiras children, where the social contact starts later. In conclusion, social changes affecting contact among children may influence varicella epidemiology. (+info)
Estimated varicella incidence on the basis of a seroprevalence survey.
(55/662)
Varicella is a disease caused by varicella-zoster virus. It is transmitted via the respiratory route, is highly communicable and mainly affects young children. An effective vaccine is now available, whose routine use is advised by health authorities in the USA and which can prevent severe disease, although breakthrough infections do occur. In deciding whether or not to include a vaccine in the routine vaccination schedule, knowledge of the morbidity of the disease in question is fundamental. Although reporting of varicella is compulsory in Catalonia, doctors only have to report the weekly number of cases diagnosed, and not their age distribution. Given that recent data on the prevalence of the infection in Catalonia according to age groups is available, it was considered that, using these data, an estimation of age-related incidence could be made. The objective of the present study was to estimate the incidence of varicella in Catalonia on the basis of the available seroprevalence data. A curve was fitted to the observed prevalence and point prevalence estimates for all ages were obtained. The incidence was derived by smoothed prevalence for each of these age groups. Estimated variance of the estimated incidence was obtained by the delta method. Predicted prevalence in the 0-4 years age group was calculated by the smoothed prevalence. The model that best fitted the sample prevalence was the exponential function. The estimated number of varicella cases in this study was 46,419 (95% CI 40,507-52,270). As the population in Catalonia in 1996 was 6,090,040, the previous results give an incidence rate of 762.2 per 100,000 persons/year with their 95% CI (666.1-858.3). The method described may be applied to the study of incidence rates in relation to the prevalence of diseases if we accept that the infection produces permanent immunity; the risk of mortality is the same for infected and non-infected subjects and that the disease incidence and population remain constant in time. (+info)
Persistence of immunity to live attenuated varicella vaccine in healthy adults.
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The varicella vaccine was approved in 1995 for use in healthy varicella-susceptible children and adults. Long-term immunity in 461 healthy adults who were enrolled in varicella vaccine trials in 1979-1999 were studied. Forty vaccinees (9%), including 19 (21%) of 89 vaccinees with household exposure (HHE) to chickenpox, developed breakthrough chickenpox 8 weeks to 11.8 years (mean, 3.3 years) after vaccination. The median number of skin lesions among the 36 untreated vaccinees was 20 (range, 1-240 lesions), and the number of lesions was essentially the same with time since vaccination. Breakthrough chickenpox was mild, even among vaccinees who did not have seroconversion or those recipients who lost detectable antibody. Lower varicella-zoster virus (VZV) antibody titers measured within 3 months of vaccination as well as at the time of HHE were associated with an increased risk of breakthrough disease. This study demonstrated that the varicella vaccine was effective in providing adults with long-term protection from serious VZV disease. (+info)