As tuberculosis continues to be the leading cause of death worldwide, we urgently need a new vaccine, scientists say
In 1921, the first effective tuberculosis vaccine was used in humans to protect against this deadly disease. However, 100 years later, in 2021, according to the World Health Organization (WHO), more than 1.6 million people worldwide have died from tuberculosis, making it the most dangerous infection again. There is now an urgent need for new vaccine options to help stop this historic killer .
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Tuberculosis is caused by the bacterium Mycobacterium tuberculosis and is spread by inhalation of droplets coughed or sneezed by infected people. These droplets can remain in suspension for an extended period of time, meaning that the risk of infection remains even after the infected person has left the room. The disease mainly affects the lungs, but in some cases it can also affect other areas such as the glands, bones, kidneys, and nervous system. Although TB is often fatal if left untreated, it can be treated with antibiotics and antimicrobials.
Until the early twentieth century, tuberculosis was one of the most common causes of death, especially among the poor in dense urban areas. Then, in 1921, Albert Calmette and Jean-Marie Camille Guerin developed their own tuberculosis vaccine, the Bacillus Calmette-Guerin (BCG) vaccine, and applied it to humans (infants who were in close contact with a tuberculosis patient). It was the first effective vaccine to protect the lungs against tuberculosis and has since become the standard vaccine.
The slow development of new alternative vaccines has not been caused by a lack of interest. More than 10 TB vaccines are currently under development, some of which are in clinical trials. The problem is that, according to Frank Kobelens, professor of global health at the University of Amsterdam and the Amsterdam Institute for Global Health and Development, “tuberculosis vaccine research and development is hampered by our limited knowledge of protective immunity, poor prediction of efficacy in humans using animal models and lack of correlates of protection (immune response required for protection).”
This basically leads to a higher risk pipeline that involves large and costly trials over a long period of time. “Basically, we don’t know if vaccines will work until they go through the clinical trial process,” Kobelens added, “which means high risk and high cost.”
Despite these challenges, there are signs of hope on the horizon. One possible approach involves an alternative route for vaccine delivery with the BCG vector. This includes individual antigens delivered by viral vectors or with an adjuvant (an ingredient used to create a stronger immune response to a vaccine).
Examples of competing vaccines: