The latest World Health Organization report on measles epidemics shows that cases jumped by 50% last year. In one of the poorest and least connected countries in the world, Madagascar, nearly a thousand children are reported to have died after a measles outbreak in the countryside. The real figure is likely to be much higher, because of difficulties of reporting. An emergency programme of vaccination seems to have contained that epidemic for the moment but it is a reminder of how devastating the disease can be against unprepared populations. In the rich world, meanwhile, previously prepared populations are having their defences dismantled from the inside.

The discovery of ad campaigns against vaccination on Facebook that are carefully targeted at pregnant women is unusually worrying. It shows how the widespread availability of sophisticated advertising techniques is going to give considerable power to people who previously had no way of getting their message across to large numbers. In the most recent US campaigns against vaccination, 147 different advertisements have been used and some viewed more than 5m times. There is an arms race under way, whether we like it or not.

Facebook and YouTube/Google must take some responsibility for the consequences of their profit-seeking algorithms. Neither company should be profiting from an activity so detrimental to public health as anti-vaccination propaganda. Both ban tobacco advertising but permit propagandising against vaccination, even from people with a commercial interest in quack remedies. Yet the withholding of children from vaccination might be considered even more anti-social than tobacco smoking. The teenager who smokes puts their own body at risk more than that of anyone else, whereas the parent who refuses a child vaccination is unlikely to harm their own health at all: only that of their offspring. If this were just a decision to allow their own children to run a small risk, it might be defended. But it is not. Because of the way that herd immunity works, such parents are threatening other people’s children too, some of whom cannot for medical reasons be vaccinated.

In some western countries threatened by campaigns against vaccination there are rules in place to stop unvaccinated children from attending school. This protects communities and sends a powerful signal to the wider world, but it is a drastic step. It risks punishing children twice for their parents’ faults.

If parents trusted the state, the medical profession, or the gatekeepers of the media, this problem would not arise. The roots of the protests against vaccination lie for a large part in the inarticulate but powerful sense that modern life is dehumanising, and that powerful forces are conspiring to turn us into obedient robots and to squeeze out our humanity. When power is no longer trusted, it does not matter that it telling the truth. Yet the distrust of anti-vaxxer parents is a threat to everyone’s children and not just their own.

One step is obviously a campaign of public education by figures who are trusted by the target audience in the way that their friends on social media are. If public health campaigns were run with half the ruthless ingenuity displayed by betting companies, we might be better off. But not everything can be left to governments and large companies. Parents who care about their own children’s health must be prepared to take the argument to the playgrounds and on to social media as well.