Age-targeted tuberculosis vaccination in China and implications for vaccine development: a modelling study

Area of Science:

• Epidemiology
• Public Health
• Vaccinology

Background:

• Tuberculosis (TB) remains a leading global cause of death, with China having the third-highest number of cases.
• The World Health Organization (WHO) has set goals to combat TB, necessitating novel interventions like vaccines.
• China's aging population presents a unique challenge for TB control, suggesting a need to consider vaccinating older adults.

Purpose of the Study:

• To model the potential impact of new tuberculosis vaccines in China.
• To compare the effectiveness of targeting adolescents versus older adults for TB vaccination.
• To inform strategic vaccine development by assessing various vaccine characteristics and implementation scenarios.

Main Methods:

• A Mycobacterium tuberculosis transmission model was calibrated using age-stratified demographic and epidemiological data from China.
• Scenarios included varying vaccine age targeting (adolescents or older adults), coverage (30% or 70%), efficacy (40-80%), duration of protection (10-20 years), and host infection status.
• Primary outcomes measured were tuberculosis incidence and mortality rate reductions by 2050 and the number needed to vaccinate (NNV) per case or death averted (2025-2050).

Main Results:

• By 2050, 74.5% of incident TB cases in China are projected to occur in individuals aged 65+, with 75.1% arising from reactivation.
• Vaccine strategies targeting older adults demonstrated higher population-level impact and lower NNV compared to adolescent-targeted strategies.
• For a 60% efficacy, 10-year protection, 70% coverage vaccine, older adult vaccination reduced incidence 1.9-157.5 times more than adolescent vaccination, with significantly lower NNV.

Conclusions:

• Adolescent-targeted TB vaccines may have limited impact in China's aging, reactivation-driven epidemic.
• Efficacious post-infection vaccines delivered to older adults are crucial for maximizing population-level impact and achieving WHO TB goals.
• Inclusion of older adults in TB vaccine clinical development and implementation planning is recommended.