What's With the New Melanoma Skin Cancer Vaccine?

Dr Sharad Paul, Chief Scientific Officer, Healthy Skin Lab
To read his blogs on general topics, visit sharadpaul.com.

This week an mRNA vaccine for melanoma, the sometimes deadly skin cancer, made the news. What do we mean by a vaccine for cancer?

COVID-19 showed the world what mRNA vaccines could do against a virus. Melanoma research is now showing us how the same technology could teach our immune system to recognise the unique genetic fingerprint of our own cancer.

One important distinction in using the term "vaccine" must be noted: the melanoma vaccine is therapeutic, i.e., a treatment, not a prevention. It is designed to reduce recurrence after cancer surgery, rather than prevent melanoma developing in the first place.

How an mRNA Cancer Vaccine Works

The technology had actually been researched for decades before the pandemic. Rather than injecting a weakened virus, mRNA vaccines deliver temporary genetic instructions that teach our cells to produce specific proteins, which the immune system then learns to recognise. During COVID-19, this meant recognising the coronavirus spike protein.

In cancer, the principle is similar. Instead of targeting a virus, we can identify mutations unique to an individual patient's tumour and create a personalised vaccine that trains their immune system to recognise cancer cells.

What the Phase 3 Trial Found

The latest results from a major Phase 3 melanoma trial, announced in October 2026, are particularly exciting. In over a thousand patients whose high-risk melanoma had been surgically removed, adding a personalised mRNA vaccine to the immunotherapy drug pembrolizumab reduced the relative risk of cancer recurrence by 42% compared with immunotherapy alone. This is a significant advance, although longer-term survival data and regulatory approval are still awaited.

As someone who has spent decades treating skin cancer, I find the possibility of designing a treatment around the genetic fingerprint of an individual patient's cancer especially compelling. We are moving towards an era where cancer treatment may become personalised.

The study included 1,137 patients from Australia, New Zealand, Europe and America. These were people who had already had their melanoma surgically removed, and still had a high risk of the melanoma coming back because it was at an advanced stage (IIB to IV). Participants were divided into two study groups:

• Two-thirds received pembrolizumab plus intismeran, a personalised mRNA vaccine made from the patient's own tumour cells by Moderna, the company that pioneered the mRNA vaccine widely used internationally. (New Zealand used a different mRNA vaccine, from Pfizer-BioNTech, during the COVID pandemic.)
• One-third received pembrolizumab alone, a known immunotherapy medication often known by the brand name Keytruda.

At 24 months, 82% of the patients who received the medication plus vaccine were alive without the cancer returning, compared to 70% in the group that received the immunotherapy medication alone. When distant metastasis-free survival (survival without distant spread of the tumour) was compared, the difference was 88% versus 80%.

Why Melanoma Matters So Much

In America, melanoma kills a person every hour. That is a terrible and sobering statistic. In New Zealand, the death rates from melanoma exceed the annual road toll from motor vehicle accidents. Australia, New Zealand's neighbour in the southern hemisphere, is the melanoma capital of the world due to the extreme heat and long sunshine hours.

Why Did Moderna's Shares Fall?

While the results are significant, the financial markets perhaps expected a bigger benefit, because shares of Moderna fell 25% when these results were leaked! This cuts to the heart of this story, which is about the testing of hypotheses, the overcoming of medical uncertainties, and the importance of vaccines.

Financial markets, however, tend to price in expectations of rapid commercial success, sometimes well before the science has matured. So when a promising cancer vaccine produces encouraging results, and not an immediate cure, investors may be disappointed even as doctors celebrate genuine progress. That may help explain why a company's share price can fall, as in this case, following apparently major medical news.

Science advances through evidence and uncertainty; financial markets move on expectations and sentiment. A medical breakthrough and a stock market disappointment can therefore happen on the very same day.

What Works Today: Prevention and Early Detection

Protecting our skin from excessive ultraviolet radiation, avoiding sunburn and recognising suspicious or changing lesions early can make an enormous difference. Melanoma detected at an early stage is often curable with relatively straightforward surgery, whereas advanced disease can require complex and expensive treatments with less predictable outcomes.

As a skin cancer doctor, I welcome every scientific breakthrough. We should never allow the excitement of tomorrow's treatments to distract us from what we know works today. The most powerful weapon against melanoma is still preventing it where possible and detecting it before it has the chance to spread. Therefore, sun protection with a good sunscreen or tinted moisturizer remains an important part of preventing skin cancer. For more on how I think about sun protection, read We Evolved to Live Under the Sun.