Is There a Breast Cancer Vaccine? Not Yet, but That Could Change

It's never fun being sick. So it's no surprise that many people don't think twice before getting their annual flu and COVID-19 vaccines. But did you ever think there would be a vaccine to prevent you from developing a condition like cancer? Or one to prevent your cancer from coming back?

It might surprise you that cancer vaccines are already available. They're divided into two different categories: vaccines to prevent cancer and vaccines to treat cancer.

When it comes to cancer prevention, the human papillomavirus (HPV) and hepatitis B vaccines have been around for quite some time. They help prevent cancers caused by these viruses. These vaccines work similarly to some flu and COVID vaccines.

Vaccines used to treat cancer work differently. They allow your immune system to better recognize and destroy cancer cells. There are cancer vaccines currently available to treat prostate, bladder, and skin cancer. But what about breast cancer? After all, it's the second most common type of cancer in women (after skin cancer).

Read on to learn about breast cancer vaccines that could be FDA approved in the future.

Is a breast cancer vaccine currently available?

Not yet. Several studies are currently testing different types of breast cancer vaccines. Some of these are showing promise. But more work needs to be done before they're proven to be safe and effective and are submitted for FDA approval.

Would a breast cancer vaccine treat or prevent breast cancer?

Scientists are looking at both approaches. But the vaccines that are farthest along in clinical studies aim to prevent cancer from coming back in people who have already been treated for their cancer.

Cancer vaccines are a type of immunotherapy. This means they help empower your immune system to fight cancer. If your cancer is growing quickly, though, sometimes immunotherapy can't work fast enough to keep up. That's why vaccines are also being evaluated in combination with chemotherapy, which can quickly kill off cancer cells. Once the bulk of cancer cells are gone, immunotherapy can continue to fight off any more that try to resurface later on.

Would a breast cancer vaccine work like a flu vaccine?

Not exactly. Flu vaccines typically contain inactivated or weakened parts of the influenza (flu) virus. Since viruses are not a normal part of your body, your immune system recognizes them as foreign and attacks them. Then, the next time your body encounters a flu virus, your body is able to recognize it and fight it off before you get sick.

By comparison, breast cancer is not caused by a virus. It needs a vaccine that works differently than a flu vaccine.

Different cancer vaccine types

Some cancer vaccines target certain proteins that contribute to cancer development. These include:

• Peptide vaccines: These vaccines contain small parts of proteins and are easy and quick to make. However, the immune response they cause may be weak and short-lived. An immune response refers to the body's ability to learn from and react to a vaccine.

• Whole-protein vaccines: These vaccines contain whole or larger parts of proteins. They're slower and more complex to make than peptide vaccines.

Other cancer vaccines in development contain genetic information that's carried into cells to activate the immune system. These are more similar to the Pfizer and Moderna COVID vaccines. Examples include:

• mRNA vaccines: These vaccines deliver mRNA, a type of genetic material, into the cells and instruct them to make proteins that activate the immune system.

• DNA vaccines: These vaccines are similar to mRNA vaccines. But they require the extra step of converting DNA into mRNA inside cells.

• Viral vector vaccines: These vaccines use a harmless virus to deliver genetic material into cells. This causes the cells to produce an immune response.

There are a few breast cancer vaccines that are currently being studied. These include peptide, whole-protein, and DNA vaccines. Even though they each have different approaches, they all aim to train the immune system to recognize and attack breast cancer cells.

What are the different stages of development for a breast cancer vaccine?

There are typically four different stages of development for new medications and vaccines. These include:

• Phase 1 studies: These clinical trials are done with a small number of people to make sure the vaccines are safe to receive.

• Phase 2 studies: These clinical trials are completed if a phase 1 trial was successful. This is a slightly larger study that switches the focus to making sure the vaccine works.

• Phase 3 studies: If things continue to progress positively, this more advanced clinical trial comes next. A phase 3 study includes a large number of people, and it compares cancer vaccines to current cancer treatments. FDA approval typically comes after successful phase 3 trials are completed.

• Phase 4 studies: These studies come after a vaccine is approved. They collect real-world data to make sure the vaccine continues to be safe to receive.

What breast cancer vaccines are currently being developed?

Breast cancer vaccines have been challenging to develop so far. This is mainly because of poor immune responses and difficulty identifying the right target(s) to go after in the body. But research remains ongoing and forward-looking.

Most breast cancer vaccines are currently in phase 1 or 2 of development. Here's an overview of the breast cancer vaccines that have the most potential so far.

GLSI-100

One vaccine, called GLSI-100, has made its way to a phase 3 clinical trial. It's a peptide vaccine that contains the HER2 protein. Some people's breast cancer cells make too much of this protein which fuels cancer growth. This is called HER2-positive breast cancer. It's an aggressive cancer that tends to come back even after it's been treated.

The GLSI-100 vaccine is designed to prompt the immune system to attack HER2-positive breast cancers. Because it's a peptide vaccine, it has to be given relatively frequently - approximately 11 injections over a 3-year period.

The phase 3 study will look at whether the vaccine increases the amount of time it takes HER2-positive breast cancer to come back. This study is estimated to be completed by the end of 2026. If all goes well, we could have a breast cancer vaccine available as early as 2027.

Plasmid-based DNA vaccine

There's another vaccine in the works that targets HER2. This one is a DNA vaccine.

In a phase 1 study, this vaccine was used to treat people with advanced HER2-positive breast cancer. It was given to people whose cancer had completely disappeared with HER2-targeted medications before the study. The ultimate goal was to prevent cancer from coming back.

Study participants were given 3 vaccine doses over a 3-month period. The vaccine was able to create a strong immune response and promote an increase in immune cells that are important for long-term protection against cancer reappearance.

After 10 years, about 85% of people who participated in the study were still alive. By comparison, only about 50% of people with the same stage of cancer typically survive for even 5 years following chemotherapy.

This vaccine progressed to the next phase of development - phase 2 clinical trials. But its manufacturer has listed the trial as "currently inactive." So it is unknown if or when this vaccine might be available.

Alpha-lactalbumin vaccine

Another breast cancer vaccine in development is a whole-protein vaccine that targets a protein called alpha-lactalbumin. This protein is normally produced in your breasts while you're breastfeeding, but disappears after you stop. It's also made in large amounts in triple-negative breast cancer (TNBC). TNBC is an aggressive type of cancer that tends to come back after treatment. Alpha-lactalbumin is a good vaccine target because outside of breastfeeding, normal breast cells don't make this protein.

In a phase 1 study, people with early TNBC who had their cancer disappear after treatment were given 3 total doses of this vaccine. Each was spaced apart by 2 weeks. More than half of people had a good immune response to the vaccine and only experienced mild side effects.

Scientists plan to further study this vaccine to see if it can prevent TNBC in people who are at high risk for developing it. They also want to see if it's effective when used with an immunotherapy medication called Keytruda (pembrolizumab).