Leprosy Vaccines: An Opportunity to Eradicate a Millennia-Old Disease

Leprosy, a chronic infectious disease caused by Mycobacterium leprae and Mycobacterium lepromatosis, remains a major public health challenge today. Despite advancements in treatment through multidrug therapy (MDT), the persistence of the disease, active transmission cases, and associated stigma continue to hinder eradication efforts. In this context, prophylactic and therapeutic vaccines are emerging as promising tools, offering a critical complementary approach to accelerate the elimination of this ancient disease.

Leprosy Vaccines: A Promising Strategy?

This study reviewed 12 randomized clinical trials assessing the efficacy of leprosy vaccines, divided into 8 prophylactic and 4 therapeutic studies. Key findings include:

• A significant reduction in infection risk was observed, with a combined relative risk of 0.61.
• Vaccines based on BCG, alone or combined with other components (e.g., Mycobacterium indicus pranii), showed varying protective effects depending on the populations studied (age, region).

Worth noting: Relative risk compares the likelihood of an event (such as disease) between two groups, indicating how many times higher or lower the risk is in one group versus another.

• Clinical severity scores, such as the Ramu score, significantly improved after administering therapeutic vaccines like Mycobacterium w.
• However, results on the bacterial index were inconsistent, suggesting a limited impact on active bacterial load.

Worth noting: The Ramu score is a clinical tool used to evaluate the severity of leprosy, considering criteria such as skin lesions, affected nerves, and internal organ involvement.

Promising Vaccines to Close a Millennia-Old Chapter

The findings indicate that leprosy vaccines, whether prophylactic or therapeutic, provide significant protection and improve clinical outcomes. However, the heterogeneity of studies, particularly in vaccination protocols and control groups, limits the generalization of conclusions.