New TB Vaccines Could Lessen Burden of Disease in Poverty-Stricken Countries

Introducing novel tuberculosis (TB) vaccines in lower-and middle-income countries (LMICs) has potential to reduce income-based inequalities in health and economic effects, according to a new study published in BMJ Global Health.

Although previous studies have projected that strengthening TB services can reduce the number of households experiencing “catastrophic” costs, there is little evidence on how new TB vaccines would contribute to achieving this worldwide goal, study authors wrote.

Using the World Health Organization (WHO) End TB target, they defined catastrophic costs as instances where patient costs of the disease—the sum of direct medical costs, direct nonmedical costs, and indirect costs—exceed 20% of a household’s annual income. National survey evidence shows that 1 in 2 patients with TB in LMICs faces catastrophic household costs, the authors said.

“Policymakers consider several issues when prioritizing health interventions,” they said. “One of the most important for diseases of poverty is impact on health equity.”

Survey evidence from high-burden countries has consistently demonstrated higher disease burden among poorer individuals, they added.

TB is one of the world’s leading causes of death from infectious disease. Although preventable and curable, the disease killed 1.5 million people in 2021. Risk factors, such as crowded living conditions, malnutrition, and factors affecting immune function are concentrated in poor and marginalized communities. Limited health care access in these communities also means that poor people may not receive prompt treatment, extending the duration and severity of their illness. Consequently, individuals sick with TB may not be able to work, leading to major economic consequences for their families.

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Prior modelling studies, using a range of assumptions, have estimated potential costs, cost savings, and cost-effectiveness of introducing novel TB vaccines in LMICs.

The goal of the present study was to estimate the potential impact of novel TB vaccines on income-based disparities seen in the health and economic consequences in LMICs. To report results by household income quintile, the researchers stratified the modelled income strata to create 5 groups of equal population size: poorest, poorer, middle, richer, and richest.

Bacillus Calmette-Guérin (BCG) is the only widely available TB vaccine, the researchers explained. However, although routinely delivered to neonates in countries with a high burden of TB, it does not offer consistent protection against all forms of TB. Further, it has minimal impact on older individuals. However, several promising TB vaccine candidates are now in late-stage trials.

In the present study, the researchers simulated the impact of novel infant and adolescent/adult vaccine products meeting the WHO preferred product characteristics for a new TB vaccine. They made assumptions about vaccine introduction based on expert opinion and historical vaccine introduction patterns. Comparing the novel TB vaccinations with a no-new-vaccine baseline, they calculated a range of health and economic outcomes in 105 LMICs for 2028 through 2050.

The data showed these findings:

• Health gains from novel vaccine introduction were greatest in lower-household-income quintiles
• The poorest 2 quintiles in each LMIC accounted for 56% of total TB cases averted
• Across all modeled countries, an adolescent/adult vaccine was projected to reduce TB incidence in the poorest quintile by 13.3 (95% CI, 10.9-15.8) million (30% of total TB cases averted compared with the no-new-vaccine baseline) and reduce the number of households experiencing catastrophic costs by 9.2 (95% CI, 7.5-11.0) million in the poorest quintile (40% of total cases of catastrophic costs averted)
• The infant vaccine was estimated to avert US$5.9 (95% CI, US$5.3-$6.5) billion in patient-incurred total costs while the adolescent/adult vaccine was estimated to avert US$38.9 (95% CI, US$36.6-$41.5) billion
• Additionally, 3.7 (95% CI, 3.3-4.1) million fewer households were projected to face catastrophic costs with the infant vaccine and 22.9 (95% CI, 21.4-24.5) million with the adolescent/adult vaccine, with 66% of gains accruing in the poorest 2 income quintiles

The study had several limitations. The characteristics of a new vaccine, once available, may differ from the various scenarios the researchers examined. In addition, the investigators assumed vaccine coverage would be the same across all income quintiles in each country. The impact of vaccination also will depend on how aggressively countries scale up a new vaccine.

Still, the results demonstrate that, when available, novel TB vaccines could help narrow income-based health and economic disparities in LMICs, the authors concluded.

“These results confirm the broad range of benefits that could be achieved by an effective TB vaccine,” they said. “While major challenges remain, successful development and introduction of a new TB vaccine has the potential to accelerate the elimination of a disease that has represented one of the greatest health threats for poor families for millennia.”

Reference

Portnoy A, Clark RA, Weerasuriya CK, et al. The potential impact of novel tuberculosis vaccines on health equity and financial protection in low-income and middle-income countries. BMJ Global Health. Published online July 8, 2023. doi:10.1136/bmjgh-2023-012466