An Overview of Tuberculosis Vaccine and Its Effectiveness Against Tuberculosis

What is Tuberculosis? Tuberculosis (TB) is an infectious disease usually caused by the bacterium Mycobacterium tuberculosis (MTB). It generally affects the lungs, but can also affect other parts of the body such as the central nervous system, lymphatic system, circulatory system, genitourinary system, bones, joints, and even skin. TB is spread through the air when people who are sick with pulmonary or laryngeal TB expel bacteria by coughing, sneezing, speaking, or spitting. TB is considered a major global health problem with 10 million new cases and 1.5 million deaths annually. What is the Tuberculosis Vaccine The BCG vaccine is a vaccine primarily used against tuberculosis. BCG is an acronym for Bacillus Calmette–Guérin, the attenuated live culture of Mycobacterium bovis used in the vaccine. This Tuberculosis Vaccine was developed in 1921 and first administered to humans in 1921 by Calmette and Guérin at the Pasteur Institute in Lille, France. It is currently recommended by the World Health Organization (WHO) and a standard part of childhood vaccination in most countries, except in Canada and the United States. How Effective is the Tuberculosis Vaccine? While the effectiveness of the BCG vaccine varies by region and study, it is estimated to be around 80% effective in preventing severe forms of TB like tuberculous meningitis or miliary TB in children. However, its effectiveness in preventing pulmonary TB (the most common form), or reactivation of latent TB, ranges from 0 to 80% with different studies showing varying results. Some of the key points regarding its effectiveness include: - It provides the best protection in children under 5 years of age against disseminated forms of TB. Protection seems to wane with time however. - Effectiveness is lower in adolescents and adults against pulmonary TB, ranging from 0-80% depending on studies. Some studies show no effectiveness, while others show up to 80% protection for a limited time period. - It does not fully prevent natural infection with MTB, but rather protects from disease in those exposed through priming of the immune response. Individuals can still get infected after vaccination. - Even with variable protection against pulmonary TB, it may reduce severity of disease if infection occurs. Overall mortality rates are reduced as well in areas with high BCG coverage. - Effectiveness varies in different geographic regions. It seems most effective in countries with high incidences of TB and is less protective in areas with lower TB rates. - Protection also reduces significantly 10-15 years post vaccination. Revaccination with new vaccines has been proposed to boost immunity long term. So in summary, while the BCG vaccine provides good protection against severe forms of TB in children, its effectiveness against pulmonary TB is quite variable depending on many factors like region, strain, time since vaccination etc. Revaccination or new vaccines may be needed for durability. Efforts to Develop New and Improved Tuberculosis Vaccine Given the variable effectiveness of BCG, especially against adult pulmonary TB, there has been significant effort in developing new and improved vaccines. Some strategies under investigation include: - Boosting BCG immunity through heterologous prime-boost strategies using viral vectors or recombinant proteins along with BCG. This aims to enhance immunity provided through increasing T cell responses. - Attenuated recombinant live vaccines using deletion mutants of MTB to induce stronger and longer lasting immunity than BCG but remain safe. VPM1002 is one such vaccine candidate currently in phase 3 trials. - Subunit vaccines consisting of combinations of MTB antigens which induce robust immune responses. M72/AS01E is a leading candidate currently in phase 3 trials. - Whole cell inactivated vaccines using whole killed mycobacteria to expose immune system to broad range of antigens simultaneously. Many candidates are currently in preclinical and early phase trials. - DNA vaccines using plasmid DNA to deliver MTB genes and induce CD4 and CD8 T cell responses. These have shown promise in animals but are still early in development. Major global efforts are ongoing through organizations like AERAS, the Bill and Melinda Gates Foundation, and various academic consortia to develop a more effective TB vaccine suitable for all age groups and global use through collaborative research. In summary, BCG provides moderate protection against severe forms of TB in children but alternatives are needed. Efforts to boost BCG immunity or develop new and improved vaccines are ongoing through approaches like subunit vaccines, viral vectored vaccines, and others. A safe and globally effective TB vaccine is crucial to control this deadly disease. Discover the language that resonates with you-

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