How the BCG Vaccine Prepares the Immune System to Combat Tuberculosis

Kate Chered
4 min readNov 28, 2023

The BCG (Bacillus Calmette-Guérin) vaccine is a cornerstone in the battle against tuberculosis (TB). Composed of live but weakened Mycobacterium bovis, it doesn’t cause disease in healthy individuals, unlike the mycobacteria found in the environment. The most common transmission of TB is through airborne droplets, though it can also spread through food or contact.

What Parents Need to Know About the BCG Vaccine for Newborns

The BCG vaccine is typically administered to newborns within the first week of life. This early vaccination is crucial as it acquaints the immune system with the TB pathogen. Post-vaccination, antibodies neutralize the weakened pathogen, and a mechanism for an immune response is established. This response is reactivated when mycobacteria enter the body again.

Where and How is the BCG Vaccine Administered to Newborns?

No special preparation is required before administering the BCG vaccine to a newborn. The vaccine is given intradermally, usually on the outer surface of the left upper arm. A light papule forms at the injection site, disappearing within 15–20 minutes.

When Should Parents Consider Delaying the BCG Vaccination?

Delaying BCG vaccination could be considered under certain medical contraindications. However, delaying the vaccine can leave a child unprotected against TB, which can be particularly severe in young children.

To Vaccinate or Not in the Maternity Hospital: Weighing the Pros and Cons

Parents may consider delaying the BCG vaccination due to personal or medical reasons. However, it’s important to understand that without the vaccine, the child’s immune system is unfamiliar with the TB pathogen, making treatment more challenging if infection occurs.

What are the Possible Complications After BCG Vaccination?

While BCG vaccination is generally safe, some complications can occur, such as minor skin reactions or lymphadenitis. However, these are rare and usually mild.

Understanding Medical Contraindications to BCG Vaccination

There are specific medical conditions where BCG vaccination is contraindicated. These include certain immune disorders or severe skin diseases.

How Do Medical Professionals in the United States View BCG Vaccination?

In the United States, the approach to BCG vaccination differs from that in Russia. The vaccine is not routinely given to all newborns, but rather to select individuals at high risk of TB.

Summary: Key Considerations for BCG Vaccination

  1. Understanding BCG Vaccine: A preventative measure against TB.
  2. Timing of Vaccination: Typically within the first week of life.
  3. Administration Site: Intradermally on the left upper arm.
  4. Potential Complications: Generally rare and mild.
  5. Medical Contraindications: Specific health conditions may warrant delay.
  6. U.S. Perspective: Administered only to high-risk individuals.

The decision to vaccinate a child in the maternity hospital or delay the BCG vaccination should be made after careful consideration of the medical advice, potential risks, and personal circumstances. The goal is always to protect the child’s health and well-being.


How Does the BCG Vaccine Work to Protect Against Tuberculosis?

The BCG vaccine introduces a weakened strain of Mycobacterium bovis to the immune system. This exposure helps the body recognize and develop a defense against the TB bacterium. When vaccinated, the immune system produces antibodies and creates a memory of the pathogen, enabling it to respond more effectively if exposed to TB in the future.

Where is the BCG Vaccine Administered on a Newborn?

The BCG vaccine is typically administered intradermally on the outer surface of the left upper arm. This location is chosen for its ease of access and the skin’s suitability for an intradermal injection, ensuring effective vaccine delivery.

What Are the Major Reasons to Delay BCG Vaccination?

Major reasons to delay BCG vaccination include certain medical conditions in the newborn, such as immune disorders or severe skin diseases. In cases where the newborn or a family member has a history of adverse reactions to vaccines, consultation with a healthcare professional is advised before proceeding with the BCG vaccination.

When Should a Newborn Receive the BCG Vaccine?

In many countries, including Russia, a newborn should receive the BCG vaccine within the first week of life, typically between the third and seventh day. This early administration is crucial for providing protection against TB, especially in areas where the disease is prevalent.

How to Determine if Your Child Should Receive BCG Vaccination in the United States?

In the United States, BCG vaccination is not routinely given to all newborns but is recommended for certain high-risk groups. This includes children living in areas with a high prevalence of TB or those who frequently travel to such areas. Consultation with a healthcare professional is essential to assess the risk and decide whether BCG vaccination is appropriate.

Originally published at on November 28, 2023.