What is Bacillus of Calmette and Guerin (BCG) Vaccine: Uses, Dosage, Side Effects and More

The Bacillus of Calmette and Guerin (BCG) vaccine is a live, weakened bacterial vaccine that helps protect against tuberculosis (TB). This vaccine has been used safely for nearly a century and contains a modified form of bacteria related to TB that can't cause the actual disease but trains your immune system to recognize and fight it.

The BCG vaccine is given as a single injection just under the skin, usually in the upper arm. While it's not routinely used in the United States, it's an important public health tool in many countries where TB is more common.

What is the BCG Vaccine?

The BCG vaccine is made from a live but weakened strain of bacteria called Mycobacterium bovis. French scientists Albert Calmette and Camille Guérin developed this vaccine in the early 1900s by carefully weakening the bacteria over many years until it could stimulate immunity without causing disease.

Think of it as a training exercise for your immune system. When you receive the vaccine, your body learns to recognize and remember the TB bacteria, so if you're ever exposed to the real thing, your immune system can respond quickly and effectively.

The vaccine is considered a "live" vaccine because it contains living bacteria, even though they've been weakened. This is different from "killed" vaccines that use dead bacteria or just pieces of bacteria.

What is the BCG Vaccine Used For?

The BCG vaccine primarily prevents tuberculosis, especially the severe forms that can affect children. It's most effective at preventing TB meningitis (when TB affects the brain and spinal cord) and disseminated TB (when TB spreads throughout the body).

In some countries, doctors also use BCG vaccine as a treatment for certain types of bladder cancer. When placed directly into the bladder, it can help stimulate the immune system to fight cancer cells.

The vaccine works best when given to infants and young children. It's less effective at preventing the lung form of TB in adults, which is why vaccination policies vary significantly between countries based on their TB rates.

How Does the BCG Vaccine Work?

The BCG vaccine is considered a moderately effective vaccine that works by training your immune system to recognize TB bacteria. When the weakened bacteria enter your body, your immune cells study them and create a memory of what TB looks like.

Your immune system then produces antibodies and activates special immune cells called T-cells that can quickly respond if you're exposed to actual TB bacteria later. This immune memory can last for many years, though it may weaken over time.

The vaccine is most effective at preventing severe, life-threatening forms of TB, particularly in children. It provides about 70-80% protection against TB meningitis and disseminated TB, but only about 50% protection against pulmonary (lung) TB in adults.

How Should I Take the BCG Vaccine?

The BCG vaccine is given as a single injection just under the skin (intradermal injection) in the upper arm. A healthcare provider will use a special needle to place the vaccine between the layers of your skin, not deep into the muscle.

You don't need to do anything special to prepare for the vaccine. You can eat normally before and after the injection, and you don't need to take it with food or water since it's not an oral medication.

The injection site should be kept clean and dry. Don't apply any creams, ointments, or bandages to the area unless your healthcare provider specifically recommends it. The injection site will likely develop a small bump and may form a scab over the following weeks.

How Long Should I Take the BCG Vaccine For?

The BCG vaccine is typically given as a single dose, usually in infancy or early childhood. Unlike some vaccines that require multiple doses or boosters, most people only need one BCG vaccination in their lifetime.

The protection from BCG vaccine can last for 10-20 years, though this varies from person to person. In most cases, booster shots are not recommended or necessary for the general population.

However, if you're using BCG as a treatment for bladder cancer, you may need multiple doses given directly into the bladder over several weeks or months. Your oncologist will create a specific treatment schedule based on your individual situation.

What Are the Side Effects of the BCG Vaccine?

Most people experience mild side effects from the BCG vaccine that are completely normal and show that your immune system is responding. The most common reaction is at the injection site, where you'll likely see changes over the next few weeks.

Here's what you can expect as normal reactions at the injection site:

• A small red bump that appears within 2-6 weeks
• The bump may become larger and sometimes develop into a small, shallow ulcer
• A scab may form and eventually fall off, leaving a small scar
• Some clear or slightly cloudy fluid may drain from the site
• Mild tenderness or soreness in the arm

These local reactions are actually signs that the vaccine is working and your body is building immunity. The healing process can take 2-6 months to complete.

Less common but still normal side effects include:

• Swollen lymph nodes in the armpit on the same side as the injection
• Mild fever (usually low-grade)
• General tiredness or feeling unwell for a day or two

These symptoms typically resolve on their own and don't require treatment.

Serious side effects are rare but can occur. Contact your healthcare provider if you experience:

• High fever (over 101°F or 38.3°C) that lasts more than 2-3 days
• Severe swelling or pain at the injection site
• Signs of infection like red streaks extending from the injection site
• Large or persistent ulcer at the injection site (larger than 1 cm)
• Swollen lymph nodes that become very large or painful

Very rare complications include widespread BCG infection, which can occur in people with severely weakened immune systems. This is why the vaccine is not given to people with certain immune system disorders.

Who Should Not Take the BCG Vaccine?

The BCG vaccine is not safe for everyone, particularly those with weakened immune systems. Since it contains live bacteria, it can potentially cause serious infections in people whose bodies can't fight off even weakened germs.

You should not receive the BCG vaccine if you have:

• HIV infection or AIDS
• Cancer affecting the immune system (like leukemia or lymphoma)
• Primary immunodeficiency disorders
• Are taking medications that suppress the immune system (like high-dose steroids or chemotherapy)
• Have had an organ transplant
• Are receiving radiation therapy

The vaccine is also not recommended for:

• Pregnant women (though it's generally safe while breastfeeding)
• People with active TB infection
• Those with severe acute illness or fever
• Anyone with a severe skin condition at the injection site
• People who have had a severe allergic reaction to a previous BCG vaccine

Additionally, infants born to mothers with HIV should not receive BCG vaccine until their HIV status is determined, as they may have inherited immune system problems.

BCG Vaccine Brand Names

The BCG vaccine is available under several brand names worldwide, though availability varies by country. In the United States, when it's used for bladder cancer treatment, it's often known by brand names like TICE BCG or TheraCys.

Different manufacturers may produce slightly different strains of the BCG bacteria, but they all work in essentially the same way. Your healthcare provider will use whichever version is available and appropriate for your specific situation.

If you're traveling internationally and need vaccination records, make sure to note which specific BCG vaccine you received, as some countries may have preferences for certain strains or manufacturers.

BCG Vaccine Alternatives

Currently, there are no widely available alternatives to the BCG vaccine for tuberculosis prevention. While researchers are working on developing new TB vaccines, BCG remains the only licensed vaccine for TB prevention worldwide.

For people who cannot receive BCG vaccine due to immune system problems, prevention focuses on avoiding exposure to TB and getting regular screening. This might include taking preventive antibiotics if you've been exposed to someone with active TB.

In terms of bladder cancer treatment, alternatives to BCG include other immunotherapies, chemotherapy drugs placed directly in the bladder, or surgical procedures. Your oncologist can discuss these options if BCG isn't suitable for you.

Is BCG Vaccine Better Than Other TB Prevention Methods?

The BCG vaccine is currently the best available tool for preventing severe forms of tuberculosis in children, but it's not perfect. It's most effective when combined with other TB prevention strategies rather than used alone.

Compared to no vaccination, BCG significantly reduces the risk of TB meningitis and disseminated TB in children. However, it provides less protection against pulmonary TB, especially in adults, which is why many countries with low TB rates don't include it in their routine vaccination programs.

The most effective TB prevention combines BCG vaccination (where appropriate) with good infection control practices, early detection and treatment of active TB cases, and preventive treatment for people at high risk of developing TB.