1. What is Tuberculosis?
Tuberculosis, or TB, is a bacterial infection that most commonly affects the lungs. For many people their immune system will fight off the infection and kill the bacteria. Sometimes the immune system stops the infection from spreading but doesn’t kill it completely. This is known as latent TB. Latent TB can become active TB infection if the immune system becomes weakened by age, medical treatment or disease. Active TB infection causes damage to the lungs. The most common signs are a persistent cough and blood-streaked mucous. If left untreated, symptoms will get worse and TB can be fatal. TB can be successfully treated with combinations of multiple antibiotics.
2. How do you catch TB?
Shingles TB is transmitted by people with active TB infection in their lungs. When coughing, droplets containing TB bacteria are spread into the air. If you breathe in these droplets you may catch the infection. Close and prolonged contact is usually needed for TB to spread, such as living with someone or working closely with them.
3. Am I at risk of catching TB?
If you live or work closely with someone who has active TB you are at high risk of catching the infection. The number of cases of TB in people born in the UK is low, but TB is much more common in some other countries. If you travel to a country with a high rate of TB, staying for more than three months and mixing with the local population you are at risk of TB. Some large UK cities have a higher rate of TB than the rest of the UK. Some occupations, such as veterinary or abattoir staff have a higher risk.
4. How does the vaccine protect me?
A vaccine is available to protect against TB. It is called the BCG vaccine and it contains a weakened strain of TB bacteria. These weakened bacteria do not cause infection for most people but do cause your immune system to develop antibodies which kill TB bacteria. If you then come into contact with the real infection your immune system will be able to fight it off.
5. Will the vaccine stop me from getting TB?
No vaccine is 100% effective and you may still develop TB even if you have been vaccinated. BCG vaccine is most effective at preventing severe disease in children under 16, providing around 70 to 80% protection. The vaccine is less effective at preventing TB infection of the lungs in adults. There have not been many studies to prove that the vaccine is effective in people over 16 and virtually no data for people over 35. That does not mean the vaccine doesn’t work if given in adulthood. Only one single dose of BCG vaccine is needed in a lifetime as it is likely to protect for up to 60 years, although protection reduces over time.
6. Why hasn’t my child been vaccinated at school?
A BCG vaccination programme has been in place in the UK since 1953. Until 2005 most children in the UK received a BCG vaccine at secondary school around the age of 12 or 13. As rates of TB have declined to low levels in most parts of the UK it was decided to stop universal vaccination in 2005. Children now only receive BCG vaccine if they are at high risk of catching TB. The vaccine is given in the first year of life, usually at around 28 days old. Older children up to 16 years old who have not been vaccinated but are at risk are still eligible for vaccination. The risk is usually because they live with someone who was born in a high-risk country.
7. Who should have the BCG vaccine?
Anyone born in the UK between about 1940 and 1993 is likely to have been given the BCG vaccine at secondary school. Nowadays, children at high risk of TB infection are identified and vaccinated in infancy. Previously unvaccinated adults and children over 16 should be vaccinated if they have an occupation that puts them at risk or they live or work for more than three months in a country with high rates of TB. Short stay tourists are not usually at risk.
8. Are there any side-effects to the vaccine?
More than 90% of people receiving BCG vaccine experience a characteristic skin reaction at the injection site. The skin at the injection site hardens and the wound may weep a little but should soon dry out. After two to three weeks a small raised bump develops which may become sore. It should heal to a small, flat scar within a few months. Your vaccinator will tell you more about this normal reaction and how to look after the skin. Other side effects are uncommon and usually involve a more severe skin reaction. A headache or high temperature may also occur and the lymph gland in the armpit may swell slightly.
9. What is a tuberculin skin test?
Before being vaccinated with BCG it is important to see if you already have antibodies to TB bacteria. This is done using a Mantoux test; another name for the tuberculin skin test. Tuberculin is a sterile mixture of proteins produced by TB bacteria. A small dose is injected right under the skin in the crook of your arm. After two to three days a skin reaction develops. The bigger the reaction the more likely you are to already have TB antibodies. If the affected skin is 5mm or bigger then the test is positive and you should not have the BCG vaccine. Mantoux testing is not usually used in children under 6 years.
References
1. Public Health England (PHE); Tuberculosis: the green book chapter 32; Published 20 March 2013, Last updated 03 August 2018; https://www.gov.uk/government/publications/tuberculosis-the-green-book-chapter-32
2. NHS: Health A–Z: Tuberculosis (TB); Last updated 12 November 2019; https://www.nhs.uk/conditions/tuberculosis-tb/
3. World Health Organization (WHO); Home/Newsroom/Fact sheets/ Detail/Tuberculosis; Updated 14-Oct-2021; https://who.int/Home/Newsroom/Fact sheets/Detail/Tuberculosis/
4. National Institute for Health and Care Excellence (NICE); Clinical Knowledge Summaries: Health Topics A-Z: Tuberculosis; Last revised January 2019; https://cks.nice.org.uk/topics/tuberculosis/
5. Summary of medicinal Product Characteristics (SmPC), BCG Vaccine AJV powder and solvent for suspension for injection; AJ Vaccines A/S, updated 19-Dec-2019. Accessed online via The electronic Medicines Compendium; https://www.medicines.org.uk/emc/product/9890
6. NHS: Health A–Z: BCG vaccine for tuberculosis (TB) overview; Last updated 26 April 2019; https://www.nhs.uk/conditions/vaccinations/bcg-tuberculosis-tb-vaccine/