CNA Explains: What we know about the Moderna, Merck breakthrough cancer vaccine

Still, experts have emphasised caution as the full results have not been released and it is not yet known precisely how much the vaccine reduced the risk of recurrence or spread.

The trial is ongoing and participants will continue to be followed to determine its effect on overall survival.

There are, however, encouraging longer-term results from an earlier, mid-stage trial.

Five-year data presented in June showed that adding the vaccine to Merck’s immunotherapy drug Keytruda, an established treatment that helps the immune system fight cancer, cut the risk of the cancer returning by half.

The combination also reduced the risk of it spreading to other parts of the body by 59 per cent, compared with Keytruda alone.

Moderna and Merck said they saw no new or increase in the rate of side effects from adding the vaccine to Keytruda.

How does the vaccine work?

This is a treatment vaccine, not a preventive vaccine. It is designed for patients who already have cancer, and its aim is to stop the disease from coming back or spreading.

The vaccine is also personalised: Each one is made based on the genetic characteristics of an individual patient’s tumour.

Doctors analyse a sample of a patient’s tumour and use mRNA technology to target specific mutations within the cancer cells. A customised jab is then designed to teach the immune system to recognise and attack those cells.  

“Even the same types of cancer – for example, melanomas – can be very different,” said Cheetham.

“So, this (treatment) uses the genetic blueprint of each individual tumour to design a vaccine that will enable your body to recognise those tumour cells better and eradicate them from the body.”

How quickly can the vaccine be available?

Despite being individually tailored, the vaccine can be produced within weeks. Each custom-made vaccine for the trial took six to eight weeks to develop.

But the treatment still needs regulatory approval before it can be widely used. The drugmakers have said they would begin filings with regulators for approval.

Cheetham believes it is realistic that the treatment could reach patients within the next two years.