60 research outputs found
Causes of variation in BCG vaccine efficacy: examining evidence from the BCG REVAC cluster randomized trial to explore the masking and the blocking hypotheses.
BCG protection varies and in some places (nearest the equator) is low or absent. Understanding this variation can inform the efforts to develop new vaccines against tuberculosis. Two main hypotheses are used to explain this variation: under masking, new vaccines are unlikely to increase protection; under blocking new vaccines have a greater potential to be effective when BCG is not. We conducted a cluster randomized trial to explored the masking and blocking hypotheses by studying BCG vaccine efficacy of neonatal vaccination and when administered for the first or a second (revaccination) time at school age in two sites (Manaus close and Salvador further south from the equator). Seven hundred and sixty three state schools were matched on socio economic characteristics of the neighborhood and 239,934 children were randomized to vaccine (BCG vaccination at school age) or control group. Protection by first BCG vaccination at school age was high in Salvador (34%, 95% CI 7-53%, p=0.017) but low in Manaus (8%, 95% CI t0 39-40%, p=0.686). For revaccination at school age, protection was modest in Salvador (19%, 95% CI 3-33%, p=0.022) and absent in Manaus (1%, 95% CI to 27-23%, p=0.932). Vaccine efficacy for neonatal vaccination was similar in Salvador (40%, 95% CI 22-54%, p<0.001) and Manaus (36%, 95% CI 11-53%, p=0.008). Variation in BCG efficacy was marked when vaccine was given at school age but absent at birth, which points towards blocking as the dominant mechanism. New tuberculosis vaccines that overcome or by pass this blocking effect could confer protection in situations where BCG is not protective
Sensibilidade e especificidade da leitura da cicatriz vacinal do BCG
OBJECTIVE: To validate the BCG scar as a marker of BCG vaccination status. METHODS: A cross-sectional survey was carried out among 53,348 schoolchildren aged 6-14 years who underwent BCG scar examination as part of a large BCG vaccine trial taking place in the city of Manaus, Brazil. Results of BCG scar reading were compared with information on vaccine status of their vaccination cards or provided by parents or guardians. Double-reading was performed in a sub-sample. Data analysis was conducted using Stata 7 and Kappa coefficient. RESULTS: Of 52,348 schoolchildren studied, vaccine status information from parents/guardian letters was available for 29,254 and from vaccination cards for 4,947. There was found a high agreement between the double-readings of the scars (Kappa=0.81). When the agreement between letter and card information was the gold standard, the sensitivity of BCG scar readings was 96.6% (95%CI 96.0-97.1) and the specificity was 71.1% (95%CI 55.7-83.7). The sensitivity was 96.1%, 97.3% and 95.3% for children vaccinated up to one month of age, four months and one year, respectively. CONCLUSIONS: Sensitivity and specificity did not show an association with the child's age at the scar reading. BCG scar was a good marker of BCG vaccination status regardless of age - from the first years of life up to 14 years old.OBJETIVO: Validar a utilização da cicatriz vacinal de BCG como um indicador de vacinação. MÉTODOS: Foi realizado um estudo transversal em 52.348 escolares, entre 6 e 14 anos de idade, que possuÃam exame de cicatriz vacinal do BCG e que participaram de um ensaio clÃnico randomizado e controlado na cidade de Manaus, Brasil. Os dados da leitura da cicatriz vacinal foram comparados com a informação sobre a vacinação passada fornecida pelos cartões vacinais ou informação dos responsáveis. Em uma subamostra foi realizada leitura dupla com cálculo do coeficiente Kappa. Para análise dos dados utilizou-se o Stata 7. RESULTADOS: Do total de 52.348 escolares estudados, 29.254 possuÃam informação sobre cicatriz vacinal coletada por meio de carta aos pais, e 4.947 possuÃam história de vacinação coletada pelo cartão de vacinas. Observou-se elevada concordância entre a dupla leitura de cicatriz vacinal (Kappa =0,81). A sensibilidade da leitura de cicatriz vacinal foi 96,6% (95% IC 96,0-97,1) e a especificidade foi 71,1% (95% IC 55,7-83,7) quando o padrão ouro utilizado foi a concordância entre a carta aos pais e a informação do cartão de vacinas. A sensibilidade foi de 96,1%, 97,3% e 95,3% para crianças vacinadas até um mês de idade, até 4 meses e até um ano de idade, respectivamente. CONCLUSÕES: Os valores encontrados para sensibilidade e especificidade foram independentes da idade da realização da leitura de cicatriz vacinal. O exame da cicatriz vacinal mostrou ser um bom indicador para avaliar a situação vacinal referente ao BCG
Evolução clÃnica de um grupo de pacientes com TB multirresistente atendidos em um centro de referência na cidade do Rio de Janeiro
Desfechos clÃnicos do tratamento de tuberculose utilizando o esquema básico recomendado pelo Ministério da Saúde do Brasil com comprimidos em dose fixa combinada na região metropolitana de Goiânia
Accuracy of a probabilistic record-linkage methodology used to track blood donors in the Mortality Information System database
Estudo dinâmico da mortalidade por tuberculose no Estado de São Paulo, Brasil: uma abordagem bayesiana
Temporal analysis of reported cases of tuberculosis and of tuberculosis-HIV co-infection in Brazil between 2002 and 2012
The Effect of Tuberculosis on Mortality in HIV Positive People: A Meta-Analysis
Tuberculosis is a leading cause of death in people living with HIV (PLWH). We conducted a meta analysis to assess the effect of tuberculosis on mortality in people living with HIV. Meta-analysis of cohort studies assessing the effect of tuberculosis on mortality in PLWH. To identify eligible studies we systematically searched electronic databases (until December 2008), performed manual searches of citations from relevant articles, and reviewed conference proceedings. Multivariate hazard ratios (HR) of mortality in PLWH with and without tuberculosis, estimated in individual cohort studies, were pooled using random effect weighting according to "Der Simonian Laird method" if the p-value of the heterogeneity test was <0.05. Fifteen cohort studies were systematically retrieved. Pooled overall analysis of these 15 studies estimating the effect of tuberculosis on mortality in PLWH showed a Hazard Ratio (HR) of 1.8 (95% confidence interval (CI): 1.4-2.3). Subanalysis of 8 studies in which the cohort was not exposed to highly active antiretroviral therapy (HAART) showed an HR of 2.6 (95% CI: 1.8-3.6). Subanalysis of 6 studies showed that tuberculosis did not show an effect on mortality in PLWH exposed to HAART: HR 1.1 (95% CI: 0.9-1.3). These results provide an indication of the magnitude of benefit to an individual that could have been expected if tuberculosis had been prevented. It emphasizes the need for additional studies assessing the effect of preventing tuberculosis or early diagnosis and treatment of tuberculosis in PLWH on reducing mortality. Furthermore, the results of the subgroup analyses in cohorts largely exposed to HAART provide additional support to WHO's revised guidelines, which include promoting the initiation of HAART for PLWH co-infected with tuberculosis. The causal effect of tuberculosis on mortality in PLWH exposed to HAART needs to be further evaluated once the results of more cohort studies become availabl
Assessing Tuberculosis Case Fatality Ratio: A Meta-Analysis
Background: Recently, the tuberculosis (TB) Task Force Impact Measurement acknowledged the need to review the assumptions underlying the TB mortality estimates published annually by the World Health Organization (WHO). TB mortality is indirectly measured by multiplying estimated TB incidence with estimated case fatality ratio (CFR). We conducted a meta-analysis to estimate the TB case fatality ratio in TB patients having initiated TB treatment. Methods: We searched for eligible studies in the PubMed and Embase databases through March 4(th) 2011 and by reference listing of relevant review articles. Main analyses included the estimation of the pooled percentages of: a) TB patients dying due to TB after having initiated TB treatment and b) TB patients dying during TB treatment. Pooled percentages were estimated using random effects regression models on the combined patient population from all studies. Main Results: We identified 69 relevant studies of which 22 provided data on mortality due to TB and 59 provided data on mortality during TB treatment. Among HIV infected persons the pooled percentage of TB patients dying due to TB was 9.2% (95% Confidence Interval (CI): 3.7%-14.7%) and among HIV uninfected persons 3.0% (95% CI: 21.2%-7.4%) based on the results of eight and three studies respectively providing data for this analyses. The pooled percentage of TB patients dying during TB treatment was 18.8% (95% CI: 14.8%-22.8%) among HIV infected patients and 3.5% (95% CI: 2.0%-4.92%) among HIV uninfected patients based on the results of 27 and 19 studies respectively. Conclusion: The results of the literature review are useful in generating prior distributions of CFR in countries with vital registration systems and have contributed towards revised estimates of TB mortality This literature review did not provide us with all data needed for a valid estimation of TB CFR in TB patients initiating TB treatmen
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