Introduction
In 2021, 1.5 million individuals died of tuberculosis (TB).1 For individuals surviving TB, the disease episode represents an extended period of ill-health, which may lead to chronic disability.2 3 This burden of disease is not evenly distributed across populations between and within countries, with many TB risk factors—crowded living conditions, malnutrition, HIV and other factors that impair immune function—concentrated in poor and marginalised communities.4 Limited healthcare access in these communities also means that individuals developing TB may not receive prompt treatment, extending the duration and severity of disease. Nationally representative TB prevalence surveys conducted in high-burden countries have consistently demonstrated higher disease burden among poorer individuals, with TB prevalence in the lowest income quintile on average 2.3 times greater than estimated for the highest income quintile.5–7
In addition to the individual health effects, TB can have major economic consequences, especially for poor households.8 Individuals sick with TB may be less able to work, resulting in income losses. TB-associated healthcare typically involves substantial out-of-pocket costs for patients, despite government-provided TB treatment being free in many countries. Observational studies have shown that individuals with TB frequently make several care-seeking attempts before an accurate diagnosis is made,9 which involves additional costs. For poorer households, these costs can represent a substantial share of available income, increasing the risks of facing catastrophic costs.8 National survey evidence shows that one in two TB-affected households face costs exceeding 20% of household annual predisease income or expenditure.10
Bacillus Calmette-Guérin (BCG) vaccine is currently the only widely available TB vaccine. While routinely delivered to neonates in countries with a high burden of TB, BCG does not offer consistent protection against all forms of TB and in all age groups and is used to reduce the high case fatality rates associated with paediatric disease but with minimal impact on transmission or disease in older individuals.11 Consequently, several new TB vaccine candidates are in late-stage trials, and their successful development could create new opportunities to prevent TB, such as increased protection compared with BCG, the prevention of all forms of TB including drug-resistant TB and reactivation of TB and effectiveness in all age groups including HIV-infected persons.
Developing new safe, affordable and effective TB vaccines that can more rapidly reduce disease incidence and mortality is essential in the End TB Strategy approved by the World Health Assembly.12 However, the concentration of TB burden among poor people in low-income and middle-income countries (LMICs) with limited purchasing power for vaccines has created additional challenges in establishing the market for these vaccines and likely delayed vaccine development. Hence, new TB vaccines will likely only be developed if there is strong financial support from the global community in order to reach global development goals. Previous studies have shown that strengthened TB services can lower patient costs and reduce the number of TB-affected households experiencing catastrophic costs.13 14 While eliminating household catastrophic costs and promoting health equity are key elements of the End TB Strategy,12 there is little evidence on how new TB vaccines would contribute to these goals. In this study, we examined the potential for new vaccines to reduce the economic burden of TB on affected households and impact health inequalities. To undertake this study, we simulated the impact of vaccine products meeting the World Health Organization (WHO) preferred product characteristics (PPCs) for a new TB vaccine.15 Comparing these vaccination scenarios to a ‘no-new-vaccine’ baseline, we calculated the potential impact on patient-incurred direct and indirect costs, as well as the number of TB-affected households experiencing catastrophic costs in 105 LMICs over the period 2028–2050. We report how these outcomes—as well as the health benefits generated by vaccine introduction—would be distributed across income quintiles, to assess the potential for new TB vaccines to affect income-based inequalities in the health and economic burden of TB.