World Immunisation Week: The fight against TB
This week is ‘World Immunisation Week’, which aims to promote vaccinations, particularly amongst the 22 million infants which are not protected with routine immunisations. This campaign coincides with the measles outbreak currently occurring in Wales, which has highlighted the importance of getting children vaccinated. The infographic in my previous post shows the breakthroughs in vaccine research which have happened since the 1950s, demonstrating the plethora of infectious diseases which have been nearly eradicated through immunisation, including Polio. There is however an ancient disease that still remains a leading global killer due to the unavailability of a efficacious vaccine: Tuberculosis (TB).
TB is the second biggest microbial killer, second to HIV; in 2011, there were 8.7 million cases of TB of which 1.4 million died. Caused by Mycobacterium Tuberculosis, the disease can be treated with antibiotics, but this can take several months due to the slow growing nature of the organism. In addition, this slow replicating nature allows resistance to arise and many cases are becoming more to difficult to treat with currently available antibiotics; now we are seeing a worrying number of extensively resistant TB cases (XDR-TB), with some cases being completely untreatable. This makes the development of an effective vaccine vital.
I remember the day I received the vaccination against TB at school, absolutely terrified by the horror stories of it leaving a ‘huge’ scar by my peers (I actually struggle to see the scar now). This Bacille Calmette-Guérin (BCG) immunization is the only available vaccine for protecting against TB which was developed in 1921. Although BCG protects children against many forms of pediatric TB, it has many drawbacks. It does not protect against pulmonary TB, which is responsible for most deaths and it’s efficacy in adults is poor.
The development of a vaccine that protects against TB in both children and adults is therefore paramount in reducing the burden of this disease. So, what is being done and what are the World Health Organisations’s (WHO) aims in combating the disease? The WHO’s goal is to reduce the global burden of TB by 2015, halving the number of deaths caused by the disease and to eliminate the disease as a global health burden by 2050. To do this, scientists are currently working to develop a new, more effective vaccination strategy, including the following approaches (see the WHO’s website for more details):
- Priming TB vaccines to replace BCG in infants.
- Early booster TB vaccines to improve the immune response induced by the priming vaccine.
- Late booster TB vaccines for those who are potentially infected without any symptoms. These vaccines are intended to reduce progression from latent to active disease.
- Vaccines for those with active TB, to be given alongside drug therapy to shorten duration of treatment.
There has been some success in developing new vaccines, with two in Phase IIa trials. There are also two in Phase IIb trials which will provide an estimation of protection. Both of these comprise of a virus expressing TB antigens. This gives us hope that a better vaccine is on the horizon, and that the WHO’s aims can be achieved.
To find out more on the WHO’s immunisation goals, including more on TB vaccine candidates, check out their website. What are your thoughts on combating TB?