Madison Clarke
The Bacille Calmette-Guérin (BCG) vaccine is a vaccine primarily used against tuberculosis (TB). It is also used to treat bladder cancer and prevent childhood tuberculous meningitis and miliary disease. The BCG vaccine is the most frequently administered vaccine worldwide and is usually given at birth in many countries outside the US. The vaccine is injected into the skin and causes some pain and scarring at the site of injection. The presence and size of the scar correlate with the magnitude of the immune response to the vaccination. However, the mechanism underlying the scar formation is not well understood.
| Characteristics | Values |
|---|---|
| Mechanism of scar formation | Not well understood |
| Scar formation | Occurs in the majority of people who receive the vaccine |
| Scar characteristics | Raised centre with rounded edges |
| Relationship with Mantoux test results | Helps to evaluate the productiveness of vaccines and identify areas where vaccination coverage might be lacking |
| Correlation with immune response | Not clear in regions like Sudan, where TB is a public health problem |
| Variability in scar formation | Observed in vaccinated children |
| Absence of scarring | May indicate a weaker immune response |
| Scar as a marker of successful vaccination | Yes |
| Administration method | Intradermal injection |
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What You'll Learn
- The BCG vaccine is primarily used against tuberculosis (TB)
- The Bacille Calmette-Guérin (BCG) vaccine is administered at birth in many countries
- Scar formation is considered a marker of successful vaccination and health benefits
- The mechanism underlying the BCG vaccine's scar formation is not well understood
- The presence and size of the scar correlate with the magnitude of the immune response
The BCG vaccine is primarily used against tuberculosis (TB)
The Bacille Calmette-Guérin (BCG) vaccine is primarily used to protect against tuberculosis (TB) disease. It is the only vaccine licensed against tuberculosis, a disease that mainly affects the lungs but can be serious if left untreated. The vaccine is particularly helpful in protecting babies and young children against more severe forms of TB, such as TB meningitis, which affects the brain.
The BCG vaccine is not routinely given in the United States or the UK, but it is administered at birth in many countries outside of the US to prevent childhood tuberculous meningitis and miliary disease. In the UK, the BCG vaccine is only given to those who meet specific criteria and in consultation with a TB expert. In the US, it is only considered for people at a high risk of getting TB, such as those who have recently moved from sub-Saharan Africa or other high-risk countries.
The BCG vaccine is a live vaccine, meaning it contains a weakened form of the tuberculosis bacteria. It is usually administered intradermally, and it can cause a false positive TB skin test reaction. The most controversial aspect of the BCG vaccine is its variable efficacy in different countries. While trials in the UK consistently show a 60 to 80% protective effect, trials conducted elsewhere have shown no protective effect, and efficacy appears to decrease the closer one gets to the equator. A 2014 meta-analysis found that the BCG vaccine reduced infections by 19-27% and reduced progression to active tuberculosis by 71%. The duration of protection is not clearly known, with some studies showing waning protection over time and others finding evidence of protection even 60 years after immunisation.
Despite the common worldwide use of the BCG vaccine, the mechanism underlying its characteristic scar formation is not well understood. Scar formation occurs in most people who receive the vaccine, and the presence and size of the scar correlate with the magnitude of the immune response to the vaccination.
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The Bacille Calmette-Guérin (BCG) vaccine is administered at birth in many countries
The Bacille Calmette-Guérin (BCG) vaccine is one of the most widely administered vaccines globally, with over 80% of neonates and infants receiving it in countries where it is part of the national childhood immunisation programme. The vaccine was developed by French physician and bacteriologist Albert Calmette and his colleague, veterinarian Camille Guérin, in 1908. It was first administered to humans in 1921. The BCG vaccine is a live attenuated vaccine form of Mycobacterium bovis, which is used to prevent tuberculosis and other mycobacterial infections. Tuberculosis is a leading cause of human disease and death, particularly in developing countries.
The BCG vaccine is typically given at birth in many countries, including Sri Lanka, Kenya, South Africa, Iran, and Australia. In some countries, such as Israel and New Zealand, the vaccine was previously administered at birth but is no longer routinely given. The World Health Organization (WHO) recommends routine neonatal vaccination in countries with a moderate to severe prevalence of tuberculosis. The vaccine is not recommended in countries with a low prevalence of tuberculosis, such as the United States.
The BCG vaccine is usually injected into the right arm, leaving a small circular scar with a raised centre and rounded edges. This scar is considered a marker of successful vaccination and 'vaccine take'. However, the mechanism underlying scar formation is not yet fully understood. The scar tends to form within 2-5 months of vaccination, and it remains stable for years.
In addition to preventing tuberculosis, the BCG vaccine has been found to offer protection against non-tuberculous mycobacterial infections like leprosy and Buruli ulcer. There is also tentative evidence of beneficial non-specific effects, such as reducing overall mortality and other health problems like sepsis and respiratory infections when given early.
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Scar formation is considered a marker of successful vaccination and health benefits
Scar formation following the Bacillus Calmette–Guérin (BCG) vaccine is considered a marker of successful vaccination and health benefits. The BCG vaccine is primarily used against tuberculosis (TB) and is typically administered to healthy babies as soon after birth as possible in countries where TB or leprosy is prevalent.
The presence and size of the scar have been correlated with the magnitude of the immune response to the BCG vaccination. A study in Sudan found that 81.4% of vaccinated children exhibited a visible BCG scar, and there was a significant association between the presence of the scar and a positive Mantoux test result. The likelihood of a positive Mantoux test, which assesses the immune response following BCG vaccination, was 3.2 times higher in children with a visible BCG scar.
The BCG vaccine has also been found to have pathogen-agnostic effects, providing protection from diseases unrelated to the intentionally targeted pathogen. For example, in Guinea-Bissau, individuals with a smallpox scar from a previous vaccination had better overall survival, and a reduced risk of HIV-1 infection was noted in studies from Denmark and Guinea-Bissau.
While the mechanism underlying scar formation is not yet fully understood, the presence of a BCG vaccine scar is generally considered a positive indicator of vaccine efficacy and health benefits.
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The mechanism underlying the BCG vaccine's scar formation is not well understood
The Bacillus Calmette–Guérin (BCG) vaccine is a vaccine primarily used against tuberculosis (TB). It is also used to prevent childhood tuberculous meningitis and miliary disease and has some effectiveness against Buruli ulcer infection and other nontuberculous mycobacterial infections. The BCG vaccine is the most frequently administered vaccine worldwide today and is usually given at birth in many countries outside the US.
The BCG vaccine is injected into the skin and causes some pain and scarring at the site of injection. The main adverse effects are keloids—large, raised scars. The insertion to the deltoid muscle is most frequently used because the local complication rate is smallest when that site is used. However, the buttock is an alternative site of administration because it provides better cosmetic outcomes.
Despite the common worldwide use of the BCG vaccine, the mechanism underlying its telltale scar is not well understood. Scar formation occurs in the majority of people who receive it, and the presence and size of the scar have been shown to correlate with the magnitude of the immune response to BCG vaccination. A study in Sudan found that out of 350 vaccinated children, 285 (81.4%) exhibited a visible BCG scar, while 65 (18.6%) did not. A significant association was found between the presence of a BCG scar and a positive Mantoux test result, with a likelihood ratio of 3.2.
The molecular mechanisms leading to skin scar formation and their role in creating systemic effects on host protection beyond the skin have not yet been delineated. However, skin scar formation following BCG vaccination is an established marker of successful vaccination and 'vaccine take'.
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The presence and size of the scar correlate with the magnitude of the immune response
The Bacille Calmette-Guérin (BCG) vaccine is a vaccine primarily used against tuberculosis (TB). It is also administered to prevent childhood tuberculous meningitis and miliary disease. The BCG vaccine is the most frequently administered vaccine worldwide and is usually given at birth in many countries.
The BCG vaccine is injected into the skin and causes some pain and scarring at the site of injection. The scar typically has a raised center with rounded edges. The presence and size of the scar correlate with the magnitude of the immune response to the BCG vaccination. This correlation is important because it helps evaluate the productiveness of the vaccine and identify areas where vaccination coverage may need improvement.
In a study of 350 vaccinated children in Omdawanban, Sudan, 81.4% exhibited a visible BCG scar, while 18.6% did not. The children with a visible scar were more likely to have a positive Mantoux test result, indicating a stronger immune response. The Mantoux test is used to assess the immune response following BCG vaccination. However, it is important to note that the correlation between scar formation and immune response may not be clear in all regions, as observed in the study from Sudan.
While the exact mechanism is not yet fully understood, the scar formation is considered a marker of successful vaccination and 'vaccine take'. The smallpox vaccine, which is no longer routinely administered, also resulted in scar formation and was associated with better overall survival and reduced risk of other infections.
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Frequently asked questions
The BCG vaccine is injected into the skin, and scarring occurs in most people who receive it. The scar is typically flat, with a raised centre and rounded edges.
Scar formation is considered a marker of successful vaccination and 'vaccine take'. The presence and size of the scar also correlate with the strength of the immune response to the BCG vaccination.
No, scar formation is not universal. A study in Sudan found that 81.4% of vaccinated children exhibited a visible BCG scar, while 18.6% did not.
The smallpox vaccine, which is generally no longer administered, also left a scar due to its unique method of administration, involving multiple punctures to the skin.
