BCG vaccination and tuberculosis prevention: A forty years cohort study, Monastir, Tunisia

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.