Bcg Vaccine - Vaccination to Preventing Tuberculosis

What is BCG vaccine?

BCG stands for Bacillus Calmette-Guérin (or Bacille Calmette-Guérin, BCG) is a vaccine against tuberculosis that is prepared to prevent the human tuberculosis diseases.  This  BCG vaccine only effective to prevent tuberculosis from infecting for only 15 years. BCG vaccine is not widely used worldwide to prevent human tuberculosis as it depends on the geographical area where the percentage of tuberculosis is high.

When is the right time to give BCG vaccine?

The used of BCG vaccine for tuberculosis prevention is best used for children under the age of 5. However, in certain cases the BCG vaccination can be taken as early age before 5 and after the children pass the 6 month age to preventing the spreading of tuberculosis. This is due to high level of infections in some countries.

Who should take BCG vaccine?

In most cases, BCG vaccine is recommended to prevent tuberculosis to children who have a negative tuberculin test and children who receive high exposure to tuberculosis infected person and people who have TB caused by strains resistant to isoniazid and rifampin. BCG vaccine also recommended to be taken to healthcare workers who strongly exposed to tuberculosis diseases in their line of work.

Who should not take BCG vaccine?

Immunosuppressed people and a pregnant woman should not be given BCG vaccine. Immunosuppressed people are people who are HIV-infected person. As there are no harmful side effects of the BCG vaccine to the fetus on the womb, it is more likely as a rumor and a further study is needed to prove it. If BCG vaccine is accidentally given to an immunocompromised patient, it can cause disseminated or life-threatening infection.

 What is the reason of BCG vaccine variable efficacy

 There are no static reason for BCG vaccine variable efficacy but a number of reason has been reported as a possible reason to support this hypothesis. As we may know, a number of percentage of tuberculosis infected person are varies accordingly between countries.

1. Background frequency of exposure to tuberculosis.  In high level infection countries the effects of immunization partially low as a large portion of TB germs may have weakened the BCG vaccine.
2. Genetic variation in BCG strains.  Not every BCG vaccine carry the same genetically strains. There is genetic variation in the BCG strains used, and this may explain the variable efficacy reported in different trials.
3. Genetic variation in populations Differences in genetic make-up of different populations may explain the difference in efficacy. The Birmingham BCG trial was published in 1988. The trial was based in Birmingham, United Kingdom, and examined children born to families who originated from the Indian subcontinent (where vaccine efficacy had previously been shown to be zero). The trial showed a 64% protective effect, which is very similar to the figure derived from other UK trials, thus refuting the genetic variation hypothesis.
4. Interference by concurrent parasitic infection Another hypothesis is that simultaneous infection with parasites changes the immune response to BCG, making it less effective. A Th1 response is required for an effective immune response to tuberculosis infection; one hypothesis is that concurrent infection with various parasites produces a simultaneous Th2-response which blunts the effect of BCG.
5.  Exposure to Ultraviolet Light Concentration of ultraviolet light (particularly UVB light) from the Sun may have some effect on efficacy of the BCG vaccine. UVB has been demonstrated to reduce efficacy of BCG vaccine in laboratory guinea pigs. The concentration gradient of UVB light increases geographically closer to the Earth's equator. It is possible, though currently unresearched, that this effect may occur as a result of sunlight-dependent Vitamin D production.