Estimation of annual risk of tuberculosis infection among children irrespective of BCG scar in the south zone of India.
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Ghana has not conducted a national tuberculin survey or tuberculosis prevalence survey since the establishment of the National Tuberculosis Control Programme. The primary objective of this study was therefore to determine the prevalence of tuberculin skin sensitivity in Ghanaian school children aged 6-10 years in 8 out of 10 regions of Ghana between 2004 and 2006.Tuberculin survey was conducted in 179 primary schools from 21 districts in 8 regions. Schools were purposively selected so as to reflect the proportion of affluent private and free tuition public schools as well as the proportion of small and large schools.Of the 24,778 children registered for the survey, 23,600 (95.2%) were tested of which 21,861 (92.6%) were available for reading. The age distribution showed an increase in numbers of children towards older age: 11% of the children were 6 years and 25%, 10 years. Females were 52.5% and males 47.5%. The proportion of girls was higher in all age groups (range 51.4% to 54.0%, p < 0.001). BCG scar was visible in 89.3% of the children. The percentage of children with a BCG scar differed by district and by age. The percentage of children with a BCG scar decreased with increasing age in all districts, reflecting increasing BCG vaccination coverage in Ghana in the last ten years. The risk of tuberculosis infection was low in the northern savannah zones compared to the southern coastal zones. Using a cut-off of 15 mm, the prevalence of infection ranged from 0.0% to 5.4% and the Annual Risks of Tuberculosis Infection 0.0% to 0.6%. There was an increase in the proportion of infected children after the age of 7 years. Children attending low and middle-class schools had a higher risk of infection than children attending upper-class schools.Tuberculosis infection is still a public health problem in Ghana and to monitor the trend, the survey needs to be repeated at 5 years interval.
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Background A Tuberculin skin test (TST) survey was conducted to assess the prevalence of latent TB Infection (LTBI) and to estimate the annual risk of M. tuberculosis infection (ARTI) in Gambian school children. The results are expected to contribute to understanding of Tuberculosis epidemiology in The Gambia. Methods This was a nationwide, multi-cluster survey in children aged 6–11 years. Districts, 20 of 37, were selected by probability proportional to size and schools by simple random sampling. All TST were performed using the Mantoux method. Height and weight measurements were obtained for all participants. We calculated prevalence of LTBI using cut-off points of 10mm, the mirror and mixture modelling methods. Results TST readings were completed 13,386 children with median age of 9 years (interquartile range [IQR] 8–10 years). Mixture analysis yielded a cut-off point of 12 mm, and LTBI prevalence of 6.9% [95%CI 6.47–7.37] and the ARTI was 0.75% [95%CI 0.60–0.91]. LTBI was associated gender and urban residence (p <0.01). Nutritional status was not associated with non-reactive TST or sizes of TST indurations. ARTI did not differ significantly by age, gender, BCG vaccination or residence. Conclusions This estimates for LTBI prevalence and ARTI were low but this survey provides updated data. Malnutrition did not affect estimates of LTBI and ARTI. Given the low ARTI in this survey and the overlapping distribution of indurations with mixture modelling, further surveys may require complementary tests such as interferon gamma release assays or novel diagnostic tools.
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The Central Chest Clinic, Bangkok, Thailand, undertook a study among child contacts of newly discovered sputum-smear-positive patients with pulmonary tuberculosis to determine the effectiveness of BCG vaccination in young children. The study design resembled that of a controlled trial except that it was retrospective for vaccination, i.e., the vaccinated and control groups were not randomly selected. For this reason a number of measures were taken to allow for the comparability of groups to be verified and for adjustments to be made if necessary. The study was initiated in September 1981 and terminated in June 1984, after 971 index cases who reported contact with young children had been registered. Registration and initial examinations were completed for 1506 child contacts. The field teams could not trace 124 reported child contacts. In the case of 8 children, the initial examination was refused. Within a week of the detection of the index case, a visit was made to the household and personal data were collected. The contact children then were offered a clinical and X-ray examination at the Central Chest Clinic for the examinations. A clinical record was prepared for each child contact, the site of BCG vaccination was covered with a dressing (even if there had been no vaccination or scar), and the pediatrician administered a clinical examination and made a full-plate postero-anterior X-ray. The X-ray picture was examined by 2 readers. Suspect children were followed up for as long as there were medical indications. When indicated by the clinical or X-ray examination, a laryngeal swab was taken for culture and gland biopsies were made and examined by histopathology and culture. If tuberculosis was strongly suspected, treatment was initiated at once with rifampicin and isoniazid. For each child a final diagnosis was made at the end of the study. A scoring system proposed by WHO was used to obtain an indication of the probability of tuberculosis. As many as 1218 (81%) of the children had a BCG scar, and among those without a scar, 35 had a record of vaccination. Vaccination coverage as well as disease risk appeared to be associated with age. Stratification by age showed that this did not affect the calculated effectiveness of BCG vaccination. Apart from age, no differences between the vaccinated and the unvaccinated children were observed that call for stratification of the material. 284 tuberculosis suspects were found, 218 among the 1253 vaccinated and 66 among the 253 unvaccinated participants. The total incidence of tuberculosis was 14.5%; it was 12.6% among the vaccinated and 23.6% among the unvaccinated. Based on the data presented in Tables 1 and 8, and adjusting for the estimated 55 vaccinated children included among those without a scar or a vaccination record, the observed efficacy is 53% with 95% confidence limits of 64% and 38%; the observed number of cases among the vaccinated is 185 less than expected. Thus, although efficacy appears less, the effectiveness is far higher than with a more stringent diagnostic criteria.
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To compare trends in direct annual risk of tuberculous infection (ARTI) during 1991-2005 in relation to tuberculosis (TB) incidence and to indirect estimates of ARTI derived from the prevalence of tuberculin skin test (TST) positivity in schoolchildren in Orel Oblast, Russia.In 2005, we abstracted annual TST results and vaccination histories from a representative sample of schoolchildren in Orel Oblast, Russia, where bacille Calmette-Guerin (BCG) vaccination and annual TST of children are nearly universal. We calculated direct ARTI based on the percentage of children tested with TST conversions each year, excluding conversions following BCG vaccination.We analysed records from 13 206 children, with a median of 10 recorded TST results per child. The ARTI increased from 0.2% in 1991 to 1.6% in 2000, paralleling trends in TB incidence. Similar results were observed when the ARTI was estimated based on prevalence of infection among children aged 3-5 years using a 12 mm cut-off to define TST positivity. Results differed substantially when 10 or 15 mm cut-offs were used or when prevalence was determined among children aged 6-8 years.ARTI measured through TST conversion increased as TB incidence increased in Orel Oblast. ARTI measured through serial TSTs can thus provide an indicator of changing trends in TB incidence.
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It is necessary to reassess tuberculosis (TB) control among Canadian Indians and Inuit, particularly the policy of BCG vaccination, because of the perceived decreased risk of TB among Indians and Inuit as well as the uncertainty surrounding BCG effectiveness due to conflicting results from several large-scale trials in different regions of the world. An attempt is made here to assess the epidemiological situation of TB among the Indian and Inuit population in Canada, to review publications on BCG and TB control, focusing on their relevance to the Canadian situation; and to consider policy options for TB control among Canada's Native population. On the basis of special studies conducted in Frobisher Bay, Northwest Territory, Brzybowski et al. estimated the annual risk of infection among the Inuit to be 3%-4% in 1971 and 1.5%-2% in 1974, ignoring tuberculin sensitivity attributed to BCG. 5 surveys over 20 years in Alaska, where mass BCG had not been applied universally, showed a marked decline in the prevalence of tuberculin sensitivity. A 1957 survey of the total population of Manitoulin Island, Ontario, which included 1475 unvaccinated Indians, revealed a prevalence of tuberculin positivity much higher than in whites in all age groups. Among Indians, 18% of the under 15, 63% of the 15-39, and 82% of the over 40 age groups were tuberculin positives. Springett concluded that vaccination was indicated in a population where not more than 20% were tuberculin positive, but the risk of new infection should exceed 10% over the next 10 years. An urgent need exists to conduct a series of tuberculin surveys of representative samples of Natives at different age groups to determine the current situation. If one wants to eliminate "false-positives" due to the effects of BCG on tuberculin sensitivity, then the suggestion that BCG be withheld from selected cohorts which are then put under intensive surveillance and tested at periodic intervals should be adopted. 2 randomized controlled trials of BCG vaccination -- the American Indian Trial and Ferguson and Sime's Saskatchewan Indian trial, initiated during the 1930s--showed high protective efficacy in the 80% range. Both were conducted at a time when the risk of infection, the case rate, and the mortality rate were all very high. A 5-year retrospective study among 2500 Inuit who were free of active disease in 1964 found that those who were vaccinated had a 1.2% mean annual incidence rate of active TB, lower than the incidence among the nonvaccinated. The complications arising from BCG vaccination usually are mild and infrequent. Research needs and policy options are outlined.
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Objective of the study: to assess the effect of the frequency of administration of the BCG vaccine on the nature and structure of clinical forms of tuberculosis (TB) in children. Materials and methods of research: a cohort observational retrospective continuous comparative multicenter crosssectional study was carried out. The data (registration form № 089/u-tube) of 3253 children of 7–14 years old with newly revealed changes in the lungs of a specific genesis, registered in 2019–2020 in the institutions of the anti-tuberculosis service of the Russian Federation were analyzed. Two comparison groups were identified: group 1 (observation group) – children who received a double injection of BCG vaccine (vaccination and revaccination) (n=184), group 2 (comparison group) – children who received a single BCG vaccination (n=3358). To achieve this goal, 5 null hypotheses were identified for testing which groups are formed from the received data array with the necessary parameters. The data were analyzed using univariate and multivariate analyzes (including confounding factors). Results: it was found that BCG revaccination does not reduce the risk of TB compared with residual changes after, it does not reduce the proportion of generalized forms of TB compared with localized forms (OR=2,4, p=0,08). The frequency of vaccination has not a statistically significant effect on the frequency of bacterial excretion (aOR=1,6, p=0,15) and destruction of lung tissue (OR=1,1, p=1). Revaccination has a statistically significant effect on the ratio of primary and secondary forms of TB, reducing the likelihood of its primary forms (aOR=0,4, p<0,001). In the course of multivariate analysis, it was found that the formation of primary or secondary TB, as well as the frequency of bacterial excretion in the comparison groups, was significantly influenced by confounding factors. Conclusion: this work has demonstrated the absence of a pronounced protective effect of repeated administration of the BCG vaccine on the clinical course of a specific process.
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