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BCG Vaccine | Current use & safety

The BCG vaccine is the only TB vaccine currently available, although there are other TB vaccines under development. Although far from perfect, the BCG vaccine is a relatively inexpensive, safe, and readily available vaccine that is still the only vaccine available for the prevention of human forms of TB.

Who is given the BCG vaccine?

The BCG vaccine is normally given to children as it has been shown to provide very good protection against the disseminated forms of TB in children, including TB meningitis. However the protection provided against pulmonary TB in adults is very variable, and so the BCG vaccine is not generally given to adults.1“Immunization surveillance, assessment and monitoring”, WHOwww.who.int/immunization_monitoring/diseases/tuberculosis/

BCG Vaccine © Pasteur Merieux Connaught, Canada

The BCG vaccine is one of the most widely used of all current vaccines, and overall it reaches more than 80% of all new born children and infants in countries where it is part of the national childhood immunization programme.2“BCG vaccine”, WHO www.who.int/biologicals/areas/vaccines/ The World Health Organisation (WHO) monitors the estimated coverage of the BCG vaccine in every country. In 2011 in countries where the aim was to vaccinate every child, levels ranged from 53% in Equatorial Guinea and 54% in Ethiopia, to more than 99.5% in India and China.3“Reported estimates of BCG coverage”, WHO//apps.who.int/immunization_monitoring/en/globalsummary/timeseries/tscoveragebcg.htm

Not every country that could do so vaccinates all children. Generally countries where there is a high level of TB use the BCG vaccine to vaccinate all children, whilst some countries with a low level of TB, such as the United States and England do not give all children BCG, but only those considered at particular risk. The United States has never vaccinated all children, but in the United Kingdom all children were given the BCG vaccine until 2005.4“The BCG World Atlas”, www.bcgatlas.org/index.php

The BCG vaccine and the TB skin test

People who have had the BCG vaccine will often then have a positive result to a TB skin test which makes it more difficult to establish whether someone has latent TB. This is one of the reasons that the BCG vaccine is not used in some countries.5“When is the BCG (TB) vaccine needed? – Vaccinations – NHS Choices”, NHS choiceswww.cdc.gov/tb/topic/testing/

The skin test will often be given before BCG vaccination. If there is a positive result to the skin test indicating that the person already has some immunity to TB, then the BCG vaccination will not be given. Giving the BCG vaccine to someone who already has some immunity, provides no benefit and could cause unpleasant side effects.6“BCG (tuberculosis) vaccination – When it is needed”, NHS Choices,www.nhs.uk/Conditions/BCG/Pages/When-it-is-needed.aspx

BCG vaccine safety issues

It is estimated that more than a billion people have received the BCG vaccine since it was first used in humans in 1921, and until recently the safety of the vaccine has not been an issue. There is though a concern now that the use of the BCG in children who are immune compromised, such as children with HIV, could result in them having an infection caused by the BCG vaccine itself. This is because the BCG vaccine contains a live but very weakened form of a bacteria called Mycobacterium bovis. This is not the same bacteria though as the bacteria that causes TB in humans, which is called Mycobacterium tuberculosis.7BCG – the current vaccine for tuberculosis, WHOwww.who.int/vaccine_research/diseases/tb/vaccine_development 8“The Difference Between Latent TB Infection and Active TB Disease”, CDC,www.cdc.gov/TB/publications/factsheets/general/LTBIandActiveTB.htm

In 2012 the there was a worldwide recall of the BCG vaccine by the manufacturer Sanofi Pasteur, after it was feared that some of the vaccine might have been contaminated during the manufacturing process.9“Tuberculosis vaccine unavailable for NZ children”, ONE News //tvnz.co.nz/national-news/tuberculosis-vaccine-unavailable-nz-children-4941809

Replacing the BCG vaccine

The organisation AERAS was set up in 2003 to develop new, safe, effective and affordable vaccines to replace the BCG vaccine. A new vaccine will need to protect against all strains of TB including the different types of drug resistant TB. The vaccine will also need to be suitable for use in preventing TB in children, adolescents and adults, as well being safe for use in people who are infected with both HIV and TB.10“AERAS – Global Efforts”, AERAS www.aeras.org/about-tb/global-efforts.php

AERAS is supporting the clinical testing of six possible new TB vaccines any one of which could be a suitable vaccine to replace the BCG vaccine. In October 2012 it was announced that in connection with Glaxo, AERAS will in 2013 begin a phase IIB study in Kenya, India and South Africa. It is planned that this vaccine if successful would be used alongside the existing BCG vaccine.11“Aera, GSK will test TB vaccine in India and Africa”, Vaccine News Daily, October 12 2012vaccinenewsdaily.com

Another potential TB vaccine also designed to be used in conjunction with BCG is MVA85A. In February 2013 the results were announced of a phase 2B trial of MVA85A.12“Safety and efficacy of MVA85A, a new tuberculosis vaccine, in infants previously vaccinated with BCG: a randomised, placebos-controlled phase 2B trials”, The Lancet, February 4 2013 www.thelancet.com/This disappointingly showed that MVA85A did not provide any significant effectiveness against either tuberculosis or M. tuberculosis infection, although some people considered that:

“the findings … are not a terminal prognosis for MVA85A, or for any of the other tuberculosis vaccines in development.”13“A major event for new tuberculosis vaccines”, The Lancet, February 4 2013 www.thelancet.com/

References

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1. “Immunization surveillance, assessment and monitoring”, WHOwww.who.int/immunization_monitoring/diseases/tuberculosis/
2. “BCG vaccine”, WHO www.who.int/biologicals/areas/vaccines/
3. “Reported estimates of BCG coverage”, WHO//apps.who.int/immunization_monitoring/en/globalsummary/timeseries/tscoveragebcg.htm
4. “The BCG World Atlas”, www.bcgatlas.org/index.php
5. “When is the BCG (TB) vaccine needed? – Vaccinations – NHS Choices”, NHS choiceswww.cdc.gov/tb/topic/testing/
6. “BCG (tuberculosis) vaccination – When it is needed”, NHS Choices,www.nhs.uk/Conditions/BCG/Pages/When-it-is-needed.aspx
7. BCG – the current vaccine for tuberculosis, WHOwww.who.int/vaccine_research/diseases/tb/vaccine_development
8. “The Difference Between Latent TB Infection and Active TB Disease”, CDC,www.cdc.gov/TB/publications/factsheets/general/LTBIandActiveTB.htm
9. “Tuberculosis vaccine unavailable for NZ children”, ONE News //tvnz.co.nz/national-news/tuberculosis-vaccine-unavailable-nz-children-4941809
10. “AERAS – Global Efforts”, AERAS www.aeras.org/about-tb/global-efforts.php
11. “Aera, GSK will test TB vaccine in India and Africa”, Vaccine News Daily, October 12 2012vaccinenewsdaily.com
12. “Safety and efficacy of MVA85A, a new tuberculosis vaccine, in infants previously vaccinated with BCG: a randomised, placebos-controlled phase 2B trials”, The Lancet, February 4 2013 www.thelancet.com/
13. “A major event for new tuberculosis vaccines”, The Lancet, February 4 2013 www.thelancet.com/