The Bacillus Calmette-Guérin (BCG) vaccine is administered to safeguard infants from tuberculosis (TB), a serious infectious disease.

The Bacillus Calmette-Guérin (BCG) vaccine utilizes a diminished strain of the bacterium responsible for tuberculosis (TB). Though attenuated, meaning it has been weakened, it does not induce tuberculosis in the recipient. Instead, it aims to bolster an infant's defense mechanisms against the disease, providing a shield against tuberculosis.

Tuberculosis, often abbreviated as TB, is a bacterial infection that predominantly targets the lungs, though it can potentially impact any body area. It's crucial to note that not everyone infected with the TB bacterium will progress to the disease state. TB disease unfolds gradually, often taking months before symptoms manifest.

Most individuals infected with TB will remain asymptomatic throughout their lives, with the bacteria lying dormant. However, in certain cases, especially among those with compromised immune systems, the dormant bacteria can activate, leading to the onset of TB.

Symptoms can differ significantly between infants and adults, underscoring the importance of identifying signs of this infectious disease in others. It is crucial to seek medical attention if you, your child, a family member, or a friend exhibit any of the following symptoms:

- A persistent cough that extends beyond three weeks
- A fever
- Night sweats
- Loss of weight without a clear reason
- An overall feeling of fatigue and malaise
- The presence of blood in coughed-up phlegm

Recognizing these symptoms early can be pivotal in timely diagnosis and treatment.

Tuberculosis (TB) transmission occurs through inhaling bacteria-laden droplets, which are expelled when an infected individual coughs. These microscopic droplets carry the TB bacteria into the air. To contract the infection, one must inhale these bacteria-containing droplets. Typically, prolonged and close contact with a person whose lungs or throat are infected – such as cohabiting in the same household – is necessary for the transmission of TB.

Various tests may be applied to diagnose tuberculosis (TB) based on the suspected form of the illness. The strategies include:

- X-rays are utilized for pulmonary TB (occurring in the lungs), and phlegm samples are examined.
- For extrapulmonary TB (located outside of the lungs): Employing CT/MRI/Ultrasound scans, endoscopy, laparoscopy, conducting urine/blood tests, performing a biopsy, and lumbar puncture.
- For latent TB (infection present without symptoms): The Mantoux skin test and the Interferon Gamma Release Assay (IGRA) blood test should be implemented.

Following the administration of the BCG vaccine, an immediate response may be observed as a raised blister at the injection site, signifying the vaccine's correct delivery. Within a period ranging from two to six weeks post-injection, a small, potentially painful spot can develop but should progressively heal, possibly leaving behind a minor scar.

In some instances, the vaccination site may evolve into a shallow ulcer. In such cases, it is advisable to maintain the area with a dry dressing until scab formation occurs, although healing could extend over several months.

Should you have concerns or suspect that the sore might be infected, it is advisable to consult your physician.