A new personalised vaccine given in combination with a drug has stopped skin cancer returning in patients during a trial, representing a potentially watershed moment in cancer treatment.

The vaccine, developed by drug companies Merck and Moderna, was given to patients with high-risk melanoma, a type of skin cancer, after they had surgery.

Early results show this new jab extended the length of time these patients were cancer free, but it’s unclear for how long, according to an announcement by the two firms.

Cancer experts say this is a breakthrough, but emphasise caution as the full results have not been released or peer-reviewed whereby independent experts examine and check the trial findings.

And even after the trials process has finished, the treatment would still need to be approved by regulators and then go through another approval process before it was made available on the NHS.

The vaccine, called Intismeran, was given in combination with Keytruda, an immunotherapy drug already used in cancer treatment.

Compared with taking the Keytruda on its own, the companies said taking the drug and vaccine together significantly increased the time patients remained cancer free and reduced the risk of the disease spreading to other organs.

The phase three trial involved more than 1,000 patients who had high-risk stage two, three or four melanoma – meaning they ranged from having large tumours in a specific area to cancers which had already spread to other parts of the body.

Merck and Moderna are calling this a personalised vaccine, meaning it works by targeting an individual patient’s tumour.

In order to create this new jab, scientists used mRNA technology – which was used for some Covid-19 vaccines – to target specific mutations within the cancer cells by surgically removing a small part of a patient’s tumour and then sequencing its DNA.

The result is a personalised anti-cancer jab which is specific to the patient’s tumour and instructs the immune system to recognise and attack any tumour cells that remain.

The two companies are testing other similar personalised vaccines for lung, bladder and kidney cancers.

Stephane Bancel, chief executive of Moderna, said the findings represent a “pivotal moment” in the field of cancer research.

Shares in both Moderna and Merck have surged since the announcement.

Cancer experts have also hailed the news as positive, but are keen to stress the findings are still early.

Dr Talisia Quallo, head of prevention and early detection at Cancer Research UK, said the research “shows promise” but said that the interim data still needs to be fully reviewed.

“It’s vital that research like this continues to be funded so that more people with cancer can have personalised treatment options to help them live longer, better lives”, she added.

Dr Lennard Lee, a consultant medical oncologist, and associate professor at the University of Oxford, said: “This is certainly good news for patients with melanoma, but the study has much wider implications. It provides proof of principle that personalised cancer vaccines work.”