[Reading Science] Tuberculosis More Terrifying Than Cancer... New Vaccine 'Cheongsinho' After 100 Years

Tuberculosis is a disease more frightening than cancer. After the development of the preventive vaccine (BCG vaccination) in 1921 and improvements in nutrition and health conditions, it was once considered a disease of developing countries. However, BCG vaccination is effective only for children and has limitations for adults. Due to its strong infectivity, long incubation period, and neglect in management caused by lack of awareness, it remains a major cause of death. In 2020, the number of tuberculosis deaths in South Korea was 1,356, which was 1.5 times higher than the 922 deaths from COVID-19. The situation is even more severe in underdeveloped countries such as those in Africa. In 2021, as many as 1.6 million people died. However, there is hope for tuberculosis eradication as a vaccine candidate with practical preventive effects, including treatment of latent infections, has entered the final clinical phase (Phase 3) after receiving massive investment for the first time in 100 years.

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The international scientific journal Nature reported on the 28th (local time) that the Bill & Melinda Gates Foundation, established by Microsoft founder Bill Gates and his ex-wife, along with the UK private research funding organization Wellcome Trust, will invest $550 million in the Phase 3 clinical trial of a tuberculosis preventive vaccine candidate developed by the global pharmaceutical company GlaxoSmithKline (GSK) and licensed to the Gates Medical Research Institute (GMRI).

Tuberculosis, caused by infection with Mycobacterium tuberculosis, is one of the most deadly infectious diseases worldwide. Looking at trends over the past 20 years, the number of cases steadily decreased after 2005 but surged during the COVID-19 pandemic due to healthcare system overload and increased cases of delayed diagnosis and treatment. The death toll rose significantly to 1.4 million in 2019, 1.5 million in 2020, and 1.6 million in 2021. Notably, two-thirds of deaths occurred in eight underdeveloped countries including Indonesia, China, the Philippines, Pakistan, Nigeria, Bangladesh, and the Democratic Republic of the Congo.

Particularly, tuberculosis bacteria can remain dormant in the body for years before becoming active and showing symptoms, making treatment difficult. It is estimated that one-quarter of the global population has latent infection with tuberculosis bacteria. Moreover, the existing BCG vaccine for tuberculosis prevention was developed a century ago in 1921 and is effective only in children, providing only moderate protection against severe disease in adults.

The tuberculosis vaccine candidate entering Phase 3 clinical trials is called M72/AS01E, with the primary goal of eliminating latent infection. It consists of a fusion protein called M72, composed of two neutralizing tuberculosis antigens, and an adjuvant AS01E. This candidate reprograms the human immune system to have high immunogenicity. In other words, it helps the immune system fight and eliminate tuberculosis bacteria upon invasion and stimulates memory T-cells to prepare the body for future infections.

In a Phase 2 clinical trial conducted in 2019, administration to adults infected with tuberculosis bacteria showed a 54% treatment efficacy, confirming its effectiveness. However, GSK abandoned further research and did not proceed to Phase 3 clinical trials, citing lack of commercial viability. Research institutions conducting the current trials, including the South African Tuberculosis Vaccine Initiative, plan to recruit about 26,000 volunteers across Asia and Africa to verify the vaccine’s effectiveness.

Tuberculosis can be cured with antibody treatment in as short as six months or as long as nine months after onset. However, the long treatment duration often leads to incomplete treatment or antibiotic resistance. This is a significant obstacle to cure, especially among impoverished populations. The research team expects that if this vaccine is developed and commercialized, it will fill these gaps.

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