Shares in the drugmakers MSD (known as Merck in the US) and Moderna have surged since both companies first hinted at the success of the vaccine in the summer.
But investors sold off stock on Thursday after financial analysts said the results were not quite as strong as those seen in an earlier, much smaller trial.
Both companies said they were now “engaging with authorities” suggesting they could file for approval from medicine regulators as soon as next year.
Widespread NHS use will also depend on cost, given that each individual patient will need to have their tumour genetically analysed and a personalised vaccine made for them.
The trial will continue so that the patients involved can be monitored – both to see if the cancer returns over time and to assess whether the drug ultimately helps them live longer.
Professor Alan Melcher from the Institute of Cancer Research in London, who wasn’t involved in the research, described the results as “very impressive”.
“It is an important proof of principle for the field, although we shouldn’t get ahead of the evidence,” he said.
“We can’t assume from one melanoma trial that the same approach will work across all cancers, and longer follow-up will be important to understand the effect on overall survival.”
The full trial results are due to be presented at a cancer conference in Madrid on Saturday.
They have yet to be published in a peer-reviewed medical journal, where they can be scrutinised by independent experts.
