The woman in charge of procuring possible COVID-19 treatments for Britain says a fully effective vaccine might never be developed, and that any early versions that do get approved might not work at all for some people.

There is no clinically proven vaccine against the coronavirus, though nearly 200 candidates are in development worldwide, and late-stage trial results are expected for the first of them by the end of 2020.

“However, we do not know that we will ever have a vaccine at all. It is important to guard against complacency and over-optimism”, Kate Bingham, the chair of the UK Vaccines Taskforce, wrote in an article published overnight in The Lancet medical journal.

“The first generation of vaccines is likely to be imperfect, and we should be prepared that they might not prevent infection but rather reduce symptoms and, even then, might not work for everyone or for long.”

NEW Viewpoint—Kate Bingham, Chair of the UK Government's Vaccine Taskforce set up by Sir Patrick Vallance lays out their strategy for protecting the UK and the world #Covid19UK https://t.co/8v9qPoZbmV pic.twitter.com/BF5F6IvNK5

— The Lancet (@TheLancet) October 28, 2020

Ms Bingham wrote that the Vaccine Taskforce recognised that “many, and possibly all, of these vaccines could fail”, adding the focus has been on jabs that are expected to elicit immune responses in those aged over 65.

Environment Minister George Eustice said on Wednesday that a vaccine would be the answer to the COVID-19 crisis, but that Ms Bingham’s analysis was “probably right.”

“It is too early to say precisely when that vaccine will come,” he told Sky News.

“There’s always a lot of doubt and uncertainty with vaccines.”

Ms Bingham also cautioned that the global manufacturing capacity for vaccines was vastly inadequate for the billions of doses that were needed, and that Britain’s manufacturing capability to date had been “equally scarce”.

With more than 900,000 infections and more than 45,000 deaths, Britain’s COVID-19 epidemic has been one of the world’s deadliest, and on Tuesday daily fatalities hit their highest level since May.

Britain has agreed supply deals for six vaccine candidates, including treatments being trialled by AstraZeneca, Sanofi and Pfizer.