Why Tuberculosis Still Kills Millions Despite a Vaccine and Effective Treatment

The BCG vaccine was first given to a human in 1921, but it still provides its strongest protection against severe tuberculosis in young children rather than reliably preventing adult pulmonary disease. Credit: Seattle Municipal Archives / CC BY 2.0 Tuberculosis killed an estimated 1.23 million people worldwide in 2024, even though the disease is preventable and curable.

Another 10.7 million people fell ill with TB that year, according to the World Health Organization (WHO). The global picture improved. The incidence rate fell 1.7% from 2023 to 2024, marking the first year-on-year decline since the COVID-19 pandemic.

But progress remains too slow. Although global TB incidence declined 12.3% between 2015 and 2024, that remains far short of the WHO End TB Strategy’s target of a 50% reduction by 2025. The contradiction helps explain why tuberculosis remains a major health threat.

A vaccine has existed for more than a century, and effective antibiotic treatment has been available for more than 80 years. Yet millions of cases still go undetected, while the conditions that allow TB to spread remain widespread. A vaccine and treatment did not make TB disappear The scientific tools used against TB are more than a century old.

Robert Koch identified the tuberculosis bacillus in 1882. Albert Calmette and Camille Guerin developed the BCG vaccine in the early 20th century, and doctors began using it in 1921. Streptomycin emerged in 1943 as the first effective antibiotic against TB.

Those breakthroughs transformed the treatment of the disease, but they did not eliminate it. BCG remains the only licensed TB vaccine and provides moderate protection against severe forms of the disease in infants and young children. The WHO says there is currently no effective vaccine for adults, either before or after exposure.

Treatment is effective but requires sustained access to diagnosis and medicines. The most widely used regimen for drug-susceptible TB lasts six months, although the WHO now recommends shorter four-month regimens for some patients. With correct diagnosis and treatment, TB can routinely be cured.

It continues to spread, however, when health systems miss cases or people cannot access care. Diagnosis and living conditions keep the disease circulating The WHO estimates that about one-quarter of the world’s population has been infected with TB bacteria. Most infected people never develop active disease, but those who do have an estimated 5% to 10% lifetime risk.

That risk increases with HIV infection, malnutrition, diabetes and tobacco use. Living conditions also influence how TB spreads. Poorly ventilated or overcrowded spaces increase the risk of exposure.

Poverty can delay diagnosis and treatment while worsening other risk factors for active disease. The diagnostic gap remains substantial. In 2024, health authorities reported 8.3 million newly diagnosed TB cases, equal to 78% of the estimated 10.7 million people who fell ill.

That left approximately 2.4 million people either undiagnosed or not officially reported to national authorities. Drug resistance adds another obstacle. The WHO estimated that 390,000 people developed multidrug-resistant or rifampicin-resistant TB in 2024, while only about two in five people with drug-resistant disease received treatment.

Historically, medical treatment has accounted for only part of the decline in TB transmission. The WHO has documented major declines in Western Europe and North America alongside improvements in living conditions, nutrition and housing. Transmission fell further after effective drug treatment became widely available.

The Americas are moving against the global trend The contrast is particularly clear in the Americas. In 2024, the WHO estimated a TB incidence rate of 33 cases per 100,000 people in the region, compared with 201 per 100,000 in South-East Asia and 207 per 100,000 in Africa. Yet the Americas have moved in the opposite direction from the global trend over the longer term.

Between 2015 and 2024, TB incidence increased 13% in the region, while the global rate declined 12.3%. The WHO says the incidence rate in the Americas increased for a fourth consecutive year in 2024. The increase reflects case-detection shortfalls during the pandemic and the region’s incomplete recovery afterward.

PAHO estimated that about 350,000 people developed TB in the Americas in 2024 and roughly 30,000 died. According to 2024 PAHO indicator data, regional incidence stood at 33.45 cases per 100,000 people. The diagnostic gap is central to the problem.

People who are not diagnosed cannot begin treatment, and untreated pulmonary TB can continue to transmit the infection. The challenge is therefore not simply the existence of a cure, but the ability of health systems to detect cases early and connect people with treatment. Colombia shows the scale of the setback Colombia illustrates the reversal.

The WHO estimated the country’s TB incidence at 46 cases per 100,000 people in 2023. A separate PAHO assessment estimated about 26,000 new TB cases in Colombia in 2024, including 1,300 cases of multidrug-resistant TB. The longer-term trend is more concerning than either annual figure alone.

Between 2015 and 2024, Colombia’s estimated TB incidence rose 47%, while mortality increased 84%. Among people with multidrug-resistant or rifampicin-resistant TB, only 55% completed treatment in 2024. The data demonstrate why vaccines and effective treatment alone have not ended TB.

BCG offers important protection against severe disease in children, but it does not reliably prevent adult pulmonary TB. Antibiotics can cure drug-susceptible TB, yet they cannot reach people who remain undiagnosed, while drug-resistant strains require more complex treatment. The global decline recorded in 2024 shows that progress is possible, but the Americas and Colombia demonstrate how quickly gains can reverse.

The central challenge is getting people diagnosed and treated before they can spread the disease. Sustained progress will depend on closing that gap while improving the conditions that continue to drive TB transmission.