Abstract
We aimed to describe incidence, trends of tuberculosis (TB) over 18 years and to evaluate the impact of the BCG vaccine after four decades of immunization program according to three protocols. We performed a cohort study including declared cases in Monastir from January 1, 2000 to December 31, 2017. We reported 997 cases of TB. The predominant site was pulmonarylocalization (n = 486). The age standardized incidence of pulmonary and lymph node TB per 100,000 inh were 5.71 and 2.57 respectively. Trends were negative for pulmonary TB (PTB) (b = - 0.82; r = -0.67; p<10−3) and positive for lymph node localization (b = 1.31; r = 0.63; p<10−3). We had not notified cases of HIV associated with TB. Crude incidence rate (CIR) of PTB per 100,000 inh was 8.17 in Non-Vaccinated Cohort (NVC) and 2.85 in Vaccinated Cohort (VC) (p < 0.0001). Relative risk reduction (RRR) of BCG vaccination was 65.1% (95%CI:57.5;71.4) for pulmonary localization and 65% (95%CI:55; 73) for other localizations. We have not established a significant RRR of BCG vaccination on lymph node TB. Protocol 3 (at birth) had the highest effectiveness with a RRR of 96.7% (95%CI: 86.6%; 99.2%) and 86% (95%CI:71%;91%) in patients with PTB and other localizations TB respectively. In Cox regression model the HR was 0.061 (95% CI 0.015–0.247) for PTB and 0.395 (95% CI 0.185–0.844) for other localizations TB in patients receiving protocol 3 compared to NVC. For lymph-node TB, HR was 1.390 (95% CI 1.043–1.851) for protocol 1 and 1.849 (95% CI 1.232–2.774) for protocol 2 compared to NVC. Depending on the three protocols, the BCG vaccine had a positive impact on PTB and other TB localizations that must be kept and improved. However, protocols 1 and 2 had a reverse effect on lymph node TB.
Highlights
Tuberculosis (TB) is one of top 10 causes of mortality in the world, responsible for 1.7 million deaths in 2016 [1]
Protocol 3; adopted from 2006 to 2017, the 6-year injection was removed;a single dose is administered at birth.Bacillus Calmette-Guerin (BCG) vaccination coverage achieved 91% in Tunisia [13]
Data were collected in the Regional Direction of Primary Health of Monastir (RDPH) of Monastir.For vaccination status, we considered Not Vaccinated Cohort (NVC) the population born before 1979, those born after as Vaccinated Cohort (VC).three cohorts were defined: VC, transient cohort and Non-Vaccinated Cohort (NVC)
Summary
Background: Tuberculosis (TB) is one of top 10 causes of mortality in the world, responsible for 1.7 million deaths in 2016 [1]. Experts from the WHO estimate that one-third of the world’s population is infected with TB, that every year 8 to 10 million new cases develop and that 3 million deaths are due to TB [2] This recrudescence is accompanied by an increase in the number of antibioticresistant strains, and by a human immunodeficiency virus (HIV)-TB coinfection [3]. BCG is believed to protect children from acquiring Mycobacterium tuberculosis infection [10] and from developing severe forms of TB disease such as TB meningitis and military TB [11] It has been forty years since the launch of BCG vaccine in Tunisia. The population-level effect of BCG vaccine varies between countries, depending on the vaccine used, implementation strategies, and vaccination coverage achieved
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