Immunization, Vaccines and Biologicals

Tuberculosis

Tuberculosis (TB) is a disease that is caused by a bacterium, which resulted in estimated 9 million new cases in 2013 and 1.5 million deaths. Over 90% of TB cases occur in low and middle income countries that have fragile healthcare infrastructures and constrained resources available, and therefore struggle to tackle one of the world’s deadliest communicable diseases.

The bacterium responsible for TB, called Mycobacterium tuberculosis (Mtb), is transmitted by people infected with pulmonary (lung) TB who release Mtb into the air through coughing, sneezing or spitting. Approximately 1/3 of the world’s population carry the disease but don’t have any symptoms (known as latent infection), however approximately 10% of these people will likely develop active disease during their lifetime and become capable of transmitting the bacterium. The TB epidemic continues in spite of an available, cost-effective and broadly implemented vaccine for infants – Bacille Calmette-Guerin (BCG) – and the carefully managed use of drugs for those who do become infected through directly observed therapy (DOTs). This is because BCG vaccination is only partially effective: it provides some protection against severe forms of pediatric non-pulmonary TB, such as TB meningitis, but is unreliable against adult pulmonary TB, which accounts for most of the TB disease burden (and transmission) worldwide. In addition, infection with Human Immunodeficiency Virus (HIV) infection can increase the likelihood of TB acquisition by up to 25-fold, and resistance to previously effective TB drug regimens is increasing.

WHO continues to recommend the vaccination of neonates with BCG, due to its protective effect in infants and young children. However, children infected with HIV through vertical transmission from their HIV-infected mother are at risk of developing severe vaccine-related disease. Therefore, children known to be HIV infected should not be vaccinated with BCG.

In 2014, the World Health Assembly adopted WHO’s End TB Strategy to eliminate the global TB epidemic by 2035, by reducing 90% of TB cases (compared to the 2015 baseline). Achieving this target is contingent on the introduction of new, more effective tools to prevent, diagnose, and treat TB. As such, new vaccines that protect against both latent and new infections of TB, in all age groups, and in all populations including those with HIV are urgently needed. It is likely that we will need more than one vaccination strategy to effectively target all sub-populations, so a variety of vaccine candidates are advancing in the clinic and their success will be essential to controlling the global TB epidemic.

WHO position papers

Prequalified vaccines

Disease burden and surveillance

Further information

Guidance on how to prioritize globally constrained BCG vaccine supply to countries – July 2015
Guidelines for National Regulatory Authorities
Vaccine safety
Immunological basis of vaccination

Resources

Links to other WHO tuberculosis related materials

Related partner links

Last updated: 12 May 2015

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