'BCG vaccine effective in fighting infection only in countries more than 40° latitude above the equator'
The vaccine against tuberculosis (TB), bacillus calmette-guerin or BCG, can also be used against TB infection, says a paper published on the website of medical journal, BMJ, It can also be effective against restricting the progression from TB infection to TB disease.
So far there has been no evidence whether the BCG vaccine, which has 60-80 per cent success against severe forms of TB in children, is effective against TB infection. Researchers from the UK for the first time assessed the evidence as to whether BCG protects against infection as well as disease.
They took data from studies conducted between 1950 and 2013 on TB patients under the age of 16 years. The primary analysis focused on whether the BCG vaccine administered prior to exposure was associated with no infection in children who had contact with infectious TB. The studies that the group analysed included four from the UK, two each from The Gambia and Spain and one each from Greece, Italy, Indonesia, Turkey, South Africa and Cambodia.
Interestingly, studies conducted above 40° latitude (UK, Spain, Greece, Italy, Turkey) showed a 26 per cent effectiveness while studies at lower latitudes 20-40° (The Gambia, Indonesia, South Africa and Cambodia) and 20-0° latitude showed no evidence of protective effect.
In conclusion, lead researcher Ibrahim Abubakar from University College London, says that the effect of the BCG vaccination would be different for high versus low tuberculosis incidence countries. They recommend that future trials need to investigate the efficacy of the vaccine against TB infection.
“If BCG is found to protect against infection it will have key implications for the use of BCG in current immunisation programmes, as well as in the future development of new improved TB vaccines,” say the researchers.
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