Millions of people annually become victims of tuberculosis, despite the fact that medical organizations are trying to increase immunization rates against this disease and treatment, limiting its spread. This is one of the leading causes of death from infectious diseases, and the number 1 among infectious killers among people living with HIV.. In 2018 alone, according to the World Health Organization (WHO), about 1.5 million people died from tuberculosis.

The vaccine used against this disease has been almost a hundred years old. Known as the BCG vaccine (Bacillus Calmette-Guerin) due to the specific strain of the causative agent of tuberculosis (Mycobacterium tuberculosis) used to create it, it effectively prevents systemic tuberculosis in young children. However, it is not as effective against the much more common pulmonary form found in both adults and adolescents..

Medical research has allowed the development of effective drugs to fight tuberculosis, and this process continues. However, multiple drug resistance has emerged, creating a new threat to the world.. Such strains of M. tuberculosis is not affected by the two most powerful anti-TB drugs currently in use worldwide.

As scientists try to find a solution to this problem, a new study reports the results when three different methods were used to immunize macaque monkeys using the BCG vaccine.. In the first group, the vaccine was delivered intravenously, in the second it was injected into the skin, and the third group received it through an aerosol can, which was inhaled. The intravenous route produced the largest number of T cells responding to bacterial antigens compared to the other two groups. T cells are part of the immune system, being lymphocytes that fight infection either directly by killing infected cells and infectious agents, or by producing antibodies, or by regulating this process..

When some of these animals were then exposed to M. tuberculosis after 6 months, scientists noticed that 9/10 animals that received the vaccine intravenously showed a high degree of protection against the disease, and 6 generally had no signs of the presence of bacteria. Thus, there was 90% protection against the pathogenic strain of tuberculosis bacteria, even when the criterion of infection was very stringent. For the first time, such a high degree of protection was achieved with BCG vaccine against pulmonary tuberculosis.. On the other hand, aerosol and intradermal immunization routes were not able to provide protection, and traces of tuberculosis were found in most animals. Scientists were taken aback, as the intravenous administration of a vaccine improved the immune response to limit the severity of the disease.. However, they did not believe that this would stop the further development of the disease.. The vaccine in the blood causes the formation of a population of T cells in the lungs, which allows you to quickly eliminate tuberculosis bacilli.

The next step is to repeat the experiments, trying to achieve the same results. This, if confirmed, could revolutionize the treatment of tuberculosis, since BCG vaccine is inexpensive and widespread..

However, it is first necessary to prove that the intravenous route is safe because the vaccine contains live, attenuated bacteria. This means that the bacteria are too weak to cause infection in people with a normal immune response..

When a vaccine is administered directly into the bloodstream, the development of various adverse reactions must be anticipated, and the risks should be studied first.. For example, if a vaccine production or storage stream allows infection with another infectious agent, or M. tuberculosis has not been sufficiently attenuated - direct injection into the blood can lead to death and disseminated infection.

Therefore, clinical trials must be preceded by a very comprehensive and thorough safety test..

If intravenous BCG vaccination can help reduce the incidence of tuberculosis, this could be a decisive step towards achieving a 90% reduction in the deaths from tuberculosis set by the United Nations Sustainable Development Goals by 2030, in addition to 50-60 million preventable deaths. In this situation, close attention should be paid to any means of increasing the effectiveness of the vaccine..

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