Falling vaccination rates for children in England have refuelled the debate over whether jabs should be compulsory for youngsters before they are allowed into schools.
The Health and Social Care Secretary Matt Hancock says he is "looking very seriously" at going down that route.
He has said repeatedly in recent months he is not ruling out compulsion.
And he told a Conservative conference fringe meeting he had received advice from officials about how the policy might be implemented.
The case for the change in policy is based on increasing official concern about falling take-up over the past five years of the measles, mumps and rubella vaccine (MMR).
In England, the vaccination rate for the first dose, usually taken round the time of a child's first birthday, fell to 90.3% in 2018-19.
So-called "herd immunity", when the disease does not spread, is achieved when uptake is at 95%.
Recently, the UK lost the measles-free status designated by the World Health Organization.
And there has been a marked decline in vaccination rates for all 13 diseases covered in jabs for children.
Social media has been blamed for spreading anti-vaccine messages and generating concern among parents.
And ministers have called for the social-media giants to do more to stop the dissemination of inaccurate information.
But with measles cases rising steadily across Europe, there is a sense in some quarters more needs to be done to stop the spread of a disease that can cause severe complications or even prove fatal.
The measles jabs are now or are about to be mandatory in France, Germany and Italy for children attending schools.
The US and Australia are among other countries where vaccinations against different diseases are compulsory for schoolchildren.
A study in BMC Medicine, in May 2019, into measles-immunisation policies in seven different healthcare systems said: "Recent policies aimed at increasing childhood immunisation rates through the introduction of compulsory vaccination are certainly producing positive effects, by raising the proportion of children protected against measles."
But some in the health and medical worlds have come out against compulsion as the right direction of travel for the UK.
They say the policy in Australia and Italy has inflamed anti-vaccine campaigners and generated more controversy.
Australia's system is based on fines and withholding state benefits for parents who fail to have their children vaccinated, a policy dubbed: "No jab, no pay."
But British Society for Immunology chief executive Dr Doug Brown said there was more scope for public information campaigns and better delivery of immunisation in local communities.
"To make this compulsory in the UK, there are concerns that it could increase current health inequities and alienate parents with questions on vaccination," he said.
"There are also major doubts about how such a policy could be implemented and monitored and risks resulting in unintended consequences as well as a loss of public confidence in vaccines."
The Royal Society for Public Health has similar reservations.
Chief executive Shirley Cramer welcomed Mr Hancock's willingness to keep all options on the table but added: "Compulsory vaccination should be a last resort.
"There are many other effective approaches to improving the uptake that should be considered."
These could include:
- targeted catch-up programmes for those who had missed out on jabs
- better reminders for parents when vaccinations were due
- focusing efforts on areas where vaccination rates were particularly low
A UK-wide compulsion policy might also be hard to justify.
Scotland and Northern Ireland have already achieved a 95% take-up for the MMR vaccine.
And there are regional variations within England. The vaccination rate in the North East was 94.5% in 2018-19, while in London it was just 83%.
The capital is seen by some as a special case as there is a more transient population, some with lower levels of knowledge of NHS community services than elsewhere.
Enforcing compulsion at schools would also be far from straightforward. Another layer of bureaucracy would have to be set up. Religious objections would have to be respected.
There are also libertarian arguments to consider. Some will argue this would be a step too far for state intervention in family life.
But the experience of other leading healthcare systems in Europe suggests implementation is feasible, if that is what elected politicians want to pursue.
Department of Health and Social Care officials and lawyers are doing the groundwork on a mandatory vaccination policy. Although, that certainly does not imply any inevitability.
Mr Hancock seems to want to test the water and tease out opinions.
And if measles cases keep rising, a major shift in health policy will edge nearer reality.