Trevor James
The Bacille Calmette-Guérin (BCG) vaccine is the only licensed vaccine against tuberculosis (TB). It is primarily given to babies and young children who are at a higher risk of contracting TB, to protect them from severe forms of the disease such as TB meningitis. The vaccine is also recommended for adults who do not have TB but are frequently exposed to it. While the BCG vaccine is effective at preventing TB in children, its efficacy in adults is variable. Studies have shown that the vaccine can reduce the risk of contracting TB by 19-27%, and progression to active TB by 71%. However, it is important to note that the BCG vaccine does not always protect against TB, and individuals who have received the vaccine should still take precautions to avoid exposure to the disease.
| Characteristics | Values |
|---|---|
| Name of vaccine | Bacillus Calmette-Guérin (BCG) vaccine |
| Main use | Vaccination against tuberculosis (TB) |
| Effectiveness | Reduces the risk of getting tuberculosis by about 50%. |
| Protection duration | Not clearly known. Studies show protection waned to 59% after 15 years and to zero after 20 years. |
| Protection in children | Effective in preventing severe disease in children under 5 years old. |
| Protection in adults | Ineffective in adolescents and adults. |
| Side effects | Uncommon and usually mild. May include a severe allergic reaction (anaphylaxis). |
| False positive test | May cause a false positive Mantoux or tuberculin skin test. |
| Administration | Administered after birth intradermally. |
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What You'll Learn
The BCG vaccine is the only licensed vaccine against TB
The Bacillus Calmette–Guérin (BCG) vaccine is the only licensed vaccine against tuberculosis (TB). It is primarily used to protect against TB, which mainly affects the lungs but can be serious if left untreated and can spread to other parts of the body. The BCG vaccine is recommended for babies and young children at a higher risk of contracting TB, especially in countries where TB is prevalent. In countries with a low prevalence of TB, only high-risk individuals are typically immunized.
The BCG vaccine is administered intradermally and can cause side effects such as a false positive Mantoux test, a type of skin test used to detect TB infection. It is important to disclose any history of the BCG vaccine when undergoing TB testing, as it can impact the accuracy of the results. The vaccine is generally not used in the United States due to low TB risk and variable effectiveness against adult pulmonary TB.
The effectiveness of the BCG vaccine varies across different regions and populations. While trials in the UK have shown a protective effect of 60-80%, trials conducted elsewhere have shown no protective effect, and efficacy appears lower in countries closer to the equator. The reasons for these variations are not fully understood but may be attributed to factors such as genetic differences, environmental changes, exposure to other bacterial infections, and laboratory conditions for growing the vaccine.
The BCG vaccine has been extensively used and celebrated its 100th anniversary in 2021. While it remains the only licensed vaccine against TB, its variable efficacy has prompted discussions about developing new vaccines with greater effectiveness, especially against adult pulmonary TB. The World Health Organization (WHO) has set the goal of eliminating tuberculosis, and addressing the limitations of the BCG vaccine is crucial in making substantial progress toward this goal.
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The vaccine is most effective for children under five
The Bacillus Calmette-Guérin (BCG) vaccine is primarily used against tuberculosis (TB). It is the only vaccine licensed against tuberculosis and is recommended for babies and young children at a higher risk of getting TB. While the effectiveness of the vaccine has been debated, with variable efficacy found in different clinical trials, a new study has provided some insight. The study found that the BCG vaccine is effective in preventing TB in children under five, with an effectiveness of about 37%.
The BCG vaccine is particularly beneficial in protecting babies and young children against severe forms of TB, such as TB meningitis, which affects the brain. It is recommended for children living with someone infected with TB, especially if the infected individual cannot take antibiotics or is infected with an antibiotic-resistant strain. The vaccine is also suggested for travellers and people at risk through their work, such as those working with high-risk groups like homeless people, asylum seekers, refugees, and prisoners.
The BCG vaccine is typically administered as a single shot soon after birth or around 28 days old. It contains a weakened form of the tuberculosis bacteria and is considered safe, with uncommon and usually mild side effects. However, it is not suitable for everyone, and a skin test is often performed before administering the vaccine to ensure the individual does not already have TB.
While the BCG vaccine is effective in young children, its protection wanes over time. Studies have shown that its effectiveness may decrease after 15 years and could wane entirely after 20 years. As a result, experts are studying and proposing new TB vaccines to supplement the BCG vaccine, with a focus on developing vaccines effective against tuberculosis in adults and older children.
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The vaccine is ineffective for adolescents and adults
The Bacillus Calmette–Guérin (BCG) vaccine is the only vaccine licensed against tuberculosis (TB). It is primarily administered to infants and young children, who are at a higher risk of contracting TB. While the BCG vaccine is effective at preventing severe forms of TB in children, its efficacy in adolescents and adults is questionable.
Several studies have indicated that the BCG vaccine's effectiveness may diminish as children grow older. A 2014 meta-analysis found that the BCG vaccine reduced infections by 19-27% and lowered the progression to active tuberculosis by 71%. However, the data on the duration of protection is inconsistent. While some studies suggest protection lasts up to 15-20 years, others have found evidence of waning immunity over time.
The variable efficacy of the BCG vaccine in different countries and populations has been a subject of debate. Trials in the UK have shown a protective effect of 60-80%, while trials in other regions have shown no protective effect. Genetic differences, environmental factors, exposure to other bacterial infections, and laboratory conditions have been proposed as possible explanations for these discrepancies.
The limitations of the BCG vaccine in adolescents and adults have prompted calls for the development of new vaccines with greater efficacy against adult pulmonary tuberculosis. Researchers have suggested that the current vaccine's effectiveness may be influenced by prior immunity induced by non-tuberculous mycobacteria, which could mask or inhibit its effects. Additionally, studies in mice have suggested that the immune response elicited by the vaccine may be too slow to control the infection effectively, allowing the bacteria to multiply.
While the BCG vaccine is widely used due to the lack of better alternatives, its limited effectiveness in adolescents and adults underscores the critical need for substantial investment in TB vaccine development. Achieving the World Health Organization's 'End TB strategy' relies on creating a more consistently effective vaccine for both adolescents and adults.
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The BCG vaccine has variable efficacy in different countries
The Bacillus Calmette–Guérin (BCG) vaccine is a vaccine primarily used against tuberculosis (TB). It is the only available vaccine against TB and is recommended for healthy babies in countries where TB or leprosy is common.
The efficacy of the BCG vaccine varies in different countries. Trials in the UK consistently show a 60 to 80% protective effect, while trials conducted elsewhere have shown no protective effect, with efficacy decreasing as one moves closer to the equator. A 1994 systematic review found that the BCG vaccine reduced the risk of getting TB by about 50%. The variable efficacy of the BCG vaccine has been attributed to several factors, including genetic differences in populations, environmental changes, exposure to other bacterial infections, and conditions in the laboratory where the vaccine is grown.
The BCG vaccine is also effective in preventing miliary tuberculosis or tuberculosis meningitis, so it is still extensively used in countries where efficacy against pulmonary tuberculosis is negligible. The development of new vaccines with greater efficacy against adult pulmonary tuberculosis may be necessary to make substantial progress in TB elimination, which is a goal of the World Health Organization (WHO).
The variable efficacy of the BCG vaccine has prompted researchers to study the mechanisms by which the vaccine works and to develop strategies to improve its efficacy. Modified administration methods and schedules have been proposed as potential ways to enhance the effectiveness of the BCG vaccine. Additionally, the influence of environmental exposures and immune responses triggered by the vaccine are being investigated to improve our understanding of its variable efficacy.
While the BCG vaccine is a critical tool in the fight against TB, its variable efficacy across different countries underscores the need for ongoing research and the development of new vaccines to address the ongoing TB pandemic effectively.
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The vaccine is not routinely administered in the US
The Bacillus Calmette–Guérin (BCG) vaccine is used to protect against tuberculosis (TB). It is the only licensed vaccine for TB, a disease that primarily affects the lungs but can spread to other parts of the body. While the BCG vaccine is routinely administered in countries where TB is prevalent, it is not routinely given in the US due to several factors:
Firstly, the low risk of infection with TB bacteria in the United States contributes to the decision not to routinely administer the BCG vaccine. Tuberculosis is less common in the US compared to other countries, and the risk of contracting TB is relatively low for most individuals.
Secondly, the variable effectiveness of the BCG vaccine, especially against adult pulmonary TB, is a factor in its limited use in the US. Clinical trials have shown inconsistent results, with some trials demonstrating a protective effect and others showing no significant impact. The efficacy of the vaccine appears to vary depending on geographical location, with lower effectiveness observed closer to the equator. This variability in effectiveness has led to a cautious approach in the US, where the vaccine is not routinely offered to the general population.
Additionally, the potential for the BCG vaccine to cause false-positive results on TB skin tests is a concern. The vaccine can induce a positive reaction on the tuberculin skin test, also known as the Mantoux test, which may lead to incorrect assumptions about TB exposure or infection. To avoid this issue, TB blood tests (interferon-gamma release assays or IGRAs) are recommended for individuals who have received the BCG vaccine. These blood tests are not affected by the vaccine and provide more accurate results.
It is important to note that while the BCG vaccine is not routinely administered in the US, it may still be considered for specific individuals who meet certain criteria. For example, people staying for extended periods in countries with a higher risk of TB may be advised to receive the vaccine. Additionally, children who are continuously exposed to untreated or ineffectively treated TB cases and cannot be separated from infected adults may be candidates for the vaccine in consultation with a TB expert.
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Frequently asked questions
The vaccine for tuberculosis (TB) is called the Bacillus Calmette-Guerin (BCG) vaccine.
No, the TB vaccine does not stop all TB infections. The BCG vaccine is the only licensed vaccine for TB, but it has shown variable efficacy.
The BCG vaccine is recommended for babies and young children who are at a higher risk of getting TB. It is also suggested for adults who do not have TB but are frequently exposed to the disease.
The effectiveness of the TB vaccine varies across different regions. Trials in the UK show a 60-80% protective effect, while other trials have shown no protective effect. A 2014 meta-analysis showed that the BCG vaccine reduced infections by 19-27% and reduced the progression to active TB by 71%.
Yes, a person can still get TB even if they have received the TB vaccine.
