Cancer vaccines – where are we?

Vaccinations (vaccines) have been a game changer in the medical world and human health. They’ve helped protect us from measles and mumps, polio, and most recently COVID-19. They’ve even eradicated smallpox, one of the deadliest diseases in human history. Can they do something similar for cancer?

Many vaccines are made from weakened or harmless versions of the virus or bacteria that they’re designed to stop. They teach our immune system how to fight off illness without actually making us ill.

Let’s take COVID-19 as an example. COVID vaccines train the body to make specific anti-COVID antibodies, blood proteins that the immune system uses to recognise and attack infections.

This means that, if you come into contact with COVID-19 at a later date the immune system knows how to fight it.

So where does cancer come into this? Well, the immune system in our bodies is one of our best defences against cancer. But cancer cells can find ways to escape it, and when they do that’s when it can develop and spread. Sometimes, the immune system needs a boost. Researchers believe cancer vaccines could be an answer.

It falls under an umbrella of treatments called cancer immunotherapy, where the immune system is utilised to reduce the size of tumours and treat cancer.

A history of vaccines and cancer

The concept of using vaccines for cancer isn’t completely new. Over the years scientists have shown associations between certain viruses and increased risk of some cancer types. For example, HPV being a cause of cervical cancer.

HPV was first linked to cervical cancer in the 1980s. It is an extremely common virus. Around 8 out of 10 people will be infected with HPV at some point in their lives. Not all cases of HPV will end up causing cervical cancer, but it can increase the risk.

The HPV vaccine is given out in a nationwide programme. Originally, it vaccinated adolescent girls against 2 strains of HPV – HPV 16 and 18. These strains are connected to around 7 in 10 cervical cancer cases. Now, the vaccine extends its protection against 9 strains of HPV and is offered to all children aged 11-13. For those who missed out on receiving it, there is a catch up programme up to the age of 25.

Results from a landmark study in 2021 showed the vaccine was effective in reducing cervical cancer risk. In fact, the vaccine was shown to reduce cervical cancer rates by almost 90% in women in their 20s who were offered it at age 12 to 13.

Similarly, Hepatitis B has been linked to liver cancer, increasing risk by 15-25%. The chance of getting the virus is low in the UK, but if you’re travelling to a country where it is more common, you can get vaccinated.

However, these are preventative examples – where vaccines are being used to prevent a virus, which in turn reduces cancer risk.

Developing vaccines against cancer itself is something different. The idea behind these vaccines is that they will be used to treat cancer, rather than preventing it.

How do cancer vaccines work?

In the same way traditional vaccines use part of the virus to prevent disease, cancer vaccines use harmless proteins from the surface of cancer cells known as antigens.

When these antigens are introduced into the body, they should stimulate the immune system to produce antibodies against them, giving it the tools to kill cancer cells.

But this isn’t straightforward. Tumours are different for every individual, and they have different antigens. So, there can’t be one universal vaccine for cancer – different vaccines will need to be created for different tumour types.

That’s not the only problem. A lot of the antigens made by tumours can look like the body’s own antigens. Using these in a vaccine could cause the immune system to target healthy cells, which can have dangerous side effects.

Thankfully, researchers have been able to identify a range of tumour-specific antigens, which aren’t found on healthy cells, and tumour-associated antigens, which are present on some normal cells. These antigens are useful markers to help the immune system target cancer cells while leaving healthy parts of the body alone.

The next step is delivering these antigens into the body. To do that, scientists are trying out lots of different cancer vaccine technologies.

Types of cancer vaccine

Protein or peptide vaccines

These vaccines are made from special proteins in cancer cells, or from small pieces of protein (peptides). They aim to stimulate the immune system to attack the cancer. Scientists have worked out the genetic codes of many cancer cell proteins, so they can make them in the lab in large quantities.

DNA and RNA vaccines

Bits of genetic material (DNA or RNA) that are usually found in cancer cells are used for these vaccines. They’re injected into the body, delivering information to the body’s cells and instructing them to make proteins that begin an immune response.

Whole cell vaccines

A whole cell vaccine uses the whole cancer cell, not just a specific cell antigen, to make the vaccine. The cancer cells are changed in the lab to make them easier for the immune system to find.

For these vaccines, scientists use the patient’s own cancer cells, another person’s cancer cells or cancer cells that were grown in the laboratory.

Dendritic cell vaccines

Dendritic cells help the immune system recognise and attack abnormal cells, such as cancer cells. To make the vaccine, scientists grow dendritic cells, a type of immune cell, alongside cancer cells in the lab. The vaccine then stimulates the immune system to attack the cancer.

Virus vaccines

Scientists can change viruses in the laboratory and use them as a type of carrier to deliver cancer antigens into the body. They change the viruses so that they cannot cause serious disease. The altered virus is called a viral vector.

Some vaccines use a viral vector to deliver cancer antigens into the body. The immune system responds to the viral vector. This then helps the immune system to recognise and respond to the cancer antigen.