One recent morning in northwest London, a group of mothers and toddlers met up in a terraced house on a quiet road. Over fruit and biscuits, they discussed the weather, breastfeeding older children, and the fact that they all refuse to vaccinate their children. The parents are part of Arnica, which brands itself as a “natural health” group for parents concerned about mainstream medicine. Arnica has a Facebook group with 37,000 members, nearly four times what it was five years ago, and has become one of the largest organisations pushing an anti-­vaccination message online.

These groups have recently grown increasingly prominent on social media—so much so that they’ve been blamed for a fall in childhood vaccination rates in the UK. After a steady rise throughout the 2000s, rates of the MMR vaccine (for Measles, Mumps and Rubella) for two-year-olds have now fallen for four successive years, and rates of most other routine childhood vaccinations also dropped in 2017-2018. A few years ago, Britain was designated “measles-free,” but it has now lost that status. In August, Boris Johnson declared that he would take on the “anti-vaxxers,” vowing to hold a conference of tech giants to establish “how they can play their part in promoting accurate information about vaccination.”

To achieve “herd immunity”—and stop a disease spreading—a certain percentage of the population must be immunised. In Britain, the NHS has a target of 95 per cent for all routine immunisations but in 2017-2018, only the six-in-one jab protecting against polio, tetanus and other diseases had more than 95 per cent coverage among children.

Like his boss, health secretary Matt Hancock has taken a hard line, saying he is “open” to making vaccines compulsory, and that groups who promote anti-vaccination messages have “blood on their hands.” Across the aisle, Labour MP Paul Sweeney said that failure to vaccinate your children should be a “criminal offence.” Social media companies have responded—Facebook announced in March that it would make these groups harder to search for, and stop promoting them in ads or recommendations. For its part, Instagram signalled it would be blocking anti-vaccination hashtags.

At first glance, the link between the rise of anti-vaxxers on social media and the fall in vaccination rates seems clear. But take a closer look at the numbers and you realise that something isn’t quite right.

Some of those opposed to vaccination share an old-school, hippieish worldview—science bad, nature good. Others worry about possible side effects. Both groups question the safety of vaccines by focusing on ingredients and the harms that might possibly result. If more and more parents were coming to share these beliefs, you would surely be able to track that. But the Vaccine Confidence Project, a research group that monitors views on the safety, efficacy and importance of immunisation, has found exactly the opposite. Between 2016 and 2018—during which time vaccine uptake for children fell across most immunisations—the proportion of Britons who strongly agreed that vaccines were safe actually increased, from 41 per cent to 47 per cent. The number who strongly disagreed shrank from 2.8 per cent to 1.5 per cent.

Public Health England released its own research earlier this year, which showed that health professionals are the most trusted source of information on vaccines. The least trusted, meanwhile, are the internet and social media. Between 2002 and 2019, the number of parents who had seen or heard something to make them doubt immunisations fell from 33 per cent to 9 per cent—a record low.

All of which leaves us with a puzzle. The recent drop in vaccinations is real, and previous vaccine scares have led to a significant rise in measles cases in England and Wales, from 284 in 2017 to 991 in 2018.

But there is no evidence that the most commonly cited cause—online anti-vaccination messages—are percolating through the population. Indeed, the opposite seems to be the case. So, what is happening? Who, or what, is to blame?

Carly Jones had no doubts about giving her oldest daughter, born in 1998, the MMR vaccine. This was despite the number of parents who were then refusing it, largely thanks to a 1998 study in the Lancet—by the now-discredited doctor Andrew Wakefield—linking the immunisation to autism. “There was a lot of that about, but I didn’t listen to it,” Jones says now. But then, aged six, her daughter was diagnosed with autism.

At the time, Jones had just given birth to her second daughter and was running her own cleaning company, working alone and at odd hours. So she went online. “I was very isolated, and I was desperate for an answer, and so I was always going to find one,” she says. On Facebook, she saw post after post linking the MMR jab with autism—drawing a parallel, for example, between the rising number of autism diagnoses and vaccination rates. (The scientific consensus is that increased diagnosis is largely explained by growing awareness and understanding, and unrelated to vaccines.)

“If doctors try to argue with these hardcore refusers, something called the ‘backfire effect’ sets in”

“My younger daughter was three or four months old, so immediately I was like, ‘OK, we’re not going to give her the MMR,’” she says. “I was post-natal and vulnerable at the time, and it just felt like something I could do to reclaim my agency, to stop this happening again.” She called her doctor’s surgery to cancel the MMR appointment, and says the receptionist simply accepted her decision. “I thought, if the receptionist thinks it’s OK for me to cancel it, maybe they all think it too.”

Then, aged two, her second daughter was diagnosed with autism too. “I realised that for a year I had left her wildly vulnerable by not getting her the vaccine. I felt absolutely awful and very, very guilty, and I still do.” She had the jabs done immediately.

Jones’s story demonstrates the impact that anti-vaccination messages can have, especially amid a mass panic like the one stirred up by Wakefield. But there are also other aspects to it: her surgery’s failure to follow up, her isolation, and her struggles as a new mum.

Jones was not a hardcore “refuser” like the Arnica parents I met. Instead, she was part of a second group of parents who don’t automatically vaccinate their children—a group Julie Leask, a professor at Sydney Nursing School, has dubbed “fence-sitters.” In a 2011 piece for Nature, “Target the Fence-Sitters,” Leask argues that only a small percentage of parents who don’t vaccinate will have “intractable views.” A larger proportion will simply be “hesitant.” Dealing with this latter group, she argues, should be the priority.

When we speak, Leask tells me that treating parents who don’t vaccinate as one homogenous group stems from an outdated model of medical training, in which “you believe patients are behaving in a certain way because they lack information about a disease, therefore you try to educate them about their disease.”

Parents who are strongly against vaccination are often middle class and educated, and tend to feel especially well educated on this particular question (others, of course, would disagree). And, to be fair, those I have spoken to have researched the subject deeply: at the Arnica mother and baby group I attended, mums pulled full scientific reports and textbooks out of their tote bags as the discussion got going. If doctors try to argue with these hardcore refusers, three studies since 2014 suggest that something called the “backfire effect” sets in. Perhaps taking umbrage at being spoken down to by medics challenging their views, they double down. “If we see facts as a panacea to this problem,” Leask says, “we are following an outdated model.”

Anna Watson, founder of Arnica and member of the European Forum for Vaccine Vigilance (EFVV), could be viewed as “intractable.” She has made complaints to CBBC after a programme showed a puppet getting vaccinated, and regularly comments on NHS disease information pages online, calling their facts on vaccination into question.

Watson had her first baby at home against healthcare professionals’ advice, and then, she tells me, “started questioning everything else.” She decided that she wouldn’t give her oldest any vaccines containing mercury (it’s no longer used in most UK vaccines). She also opted against the live polio vaccine because she was worried about the side effects and “there have been no cases of polio [in the UK] for years.” After further research, she eventually decided to give her next child no vaccines at all. A few “myth-busting” leaflets given out by a doctor would plainly not change her mind.

Even Watson is under no illusion, though, about the fact that hers are minority views. She says that while the number of members in the Arnica Facebook group has swelled in the past five years, the size of the meetup groups “hasn’t changed” much, and indeed that the number of monthly posts on the Facebook group has halved in the past year. She also describes a sense of “weariness” and “despair” among campaigners, because of social media clampdowns on vaccine questioning groups and the possibility of mandatory vaccines.

Michael Blastland, co-creator of More or Less, a Radio 4 programme about numbers in public debate, believes that campaigners like Watson have a set, skewed impression of the risks of vaccination compared to the risks of disease: “No amount of data will persuade them, however you present it, since they contest the basis of the data. And since they deny the link between vaccination and low rates of disease, and attribute those low rates to something else, the only thing that will get to people like this is that their kid gets something terrible, or there’s a catastrophic epidemic when the vaccination rates drop. Even then, some would probably allege a conspiracy.”

The “fence-sitters,” however, may well be open to reframing their understanding of the risks. Blastland says that simply presenting the numbers more clearly can work: “You can compare low risks [of side effects from the vaccines] to other hazards that help people understand the magnitudes, or you can change the framing. That is, instead of presenting the chance of an adverse reaction from a jab, you can present the chances of being OK.”

Another issue with the “knowledge deficit” model when applied to parents who don’t vaccinate is the reality that a very, very low number of children can indeed be adversely affected by vaccines­—a fact public health messages are understandably wary about advertising. But if the authorities keep quiet, and parents go on to uncover relevant information themselves—like, for example, the fact that £74m has been paid out by the UK’s Vaccine Damage Payment Fund since 1978—they may feel they have been lied to.

Given that several vaccine rates in the UK are now below the WHO’s recommended levels for herd immunity, communication with both hardcore refusers and fence-sitters is worth trying, even if it’s likely the hardcore refusniks in particular will never be convinced. With both these groups, though, the problem is a lack of confidence in vaccines, in an era where overall confidence has been rising. If we want to explain the population-wide drop in takeup, we need to look for another, invisible, expanding group: those who simply don’t vaccinate, despite believing that they are safe and effective.

When Leask first started investigating unvaccinated children in Australia for her PhD, she, like health secretary Hancock and prime minister Johnson, thought the cause was clear: the spread of anti-vaxxer messages. “But I kept coming up against what were, at the time, inconvenient facts,” she says now. As in the UK today, she couldn’t find solid evidence that anti-vaccination messages were on the rise.

Instead, she began to identify a third group: the passive non-immunisers. “This is where someone is facing barriers to getting to the healthcare service on time, making appointments, or their kids are sick so they can’t have the vaccine on time. They are the more practical and logistical issues which are overlooked in the public discourse. Barring occasional large-scale scares, she says, “the biggest enemy of good vaccination rates” is disruption to “the primary care system.”

So are campaigns against truth-denying fanatics themselves running ahead of reality? Helen Bedford, Professor of Children’s Health at UCL, has spent three decades investigating attitudes to immunisation, and tells me, bluntly, that there’s “no evidence” to suggest that the number of people actively deciding not to vaccinate their kids is rising. Instead, she agrees with Leask that some parents, especially exhausted new ones, face problems making appointments and fitting them into the diary. She also points out something else that happened in 2015, the year the recent decline in MMR uptake began: the final reforms to the health system by the former health secretary Andrew Lansley were implemented.

These reforms rewired the entire NHS in confusing ways. The boundary between health service and local authority duties for public health was redrawn, and some expertise went missing between the dissolution of one set of health service bodies and the creation of differently shaped replacements. But the chief practical effect for vaccines was that the newly created Screening and Immunisation Teams were responsible for much larger areas than their equivalent under the old system.

“In the past,” Bedford explains, “they had an immunisation co-ordinator who would be responsible for one area and know the area really well and do regular follow-ups.” The former director of immunisation for the Department of Health, David Salisbury, this year put forward a similar case, further arguing that NHS England, the new central body created by Lansley to run the health service, “had little immunisation expertise or capacity.”

“One mother told me, ‘Can you write somewhere that it’s really hard, trying to do the right thing?’”

Meanwhile, the number of health visitors—who provide a crucial link into the NHS for new parents, and whose number the Cameron government originally made a virtue of ramping up—fell from a high of 10,309 in October 2015 to 7,694 at the beginning of this year.

Another woman I interviewed, Mel (she didn’t want her full name to be included), realised last month that her younger son, now nine, did not have his second MMR vaccination. She remembers that she fully intended to get it done, “but they were giving him a couple of others at the same time. It felt like too much stuff going into him, so I said I’d take him back for the injection and never got round to it.” She says booking doctor’s appointments was difficult, but the biggest issue was that her doctor never followed up with a letter or text when she didn’t get the second injection done.

Punam Krishan, a GP, points out that the UK as a whole is very lucky that the NHS everywhere offers a “full vaccination schedule free of charge.” Elsewhere in Europe, there are greater practical barriers: in France, where vaccine confidence levels are notably low, you must buy the vaccine from a pharmacy and then get it done at a doctor’s surgery. Krishan believes that pop-up vaccination clinics at accessible times for parents, such as early mornings, evenings and weekends, would help the UK bring uptake back up again.

The three broad groups who are not vaccinating—the fence-sitters, the ardent anti-vaxxers, and the “accidental non-vaxxers”—are all very different, and must be communicated with in different ways. But they do have some things in common. A study in the journal Vaccine drew on interviews with 24 parents during the catch-up MMR campaign in the mid-2000s. Some were planning to vaccinate, others to postpone, and others to decline. The researchers noted that across the three categories, there was a striking similarity: “parents expected and feared guilt if their chosen course of action resulted in a negative outcome for their child.”

One parent interviewed as part of the study described the bind some parents find themselves in while making the decision: “If she got one of the diseases and then I’d feel guilty for the rest of my life for not having given her the jab. But then again, if she got autism, I’d feel exactly the same.”

In practice with MMR, this logic is flawed: the autism link has been disproved. But it is hard not to have sympathy. Making medical decisions is hard enough—making them on behalf of your own child is harder again. And, in theory at least, the proper objectives of public health (minimising population-wide infection rates) and the individual parent (minimising the individual risks of potential infection and potential side effects in their own child) can diverge.

When I was researching an article back in 2014, I met a mum who had been anti-vaccination for 20 years, and had confidently shown me the various scientific studies which she had used to make her decision. As I was leaving, she stopped me. “Can you write somewhere that it’s really hard, trying to do the right thing?” she said. “People say you’re a bad mother; that you’re putting your child’s life at risk, but you can only do what you think is best. You’d never forgive yourself otherwise.”

Introducing a policy of mandatory vaccination, when viewed in the context of all three groups who aren’t vaccinating, seems very risky. It will further alienate the hardcore group, and could result in those children being banned from school. By removing any element of parental choice, it could lend credibility to conspiracies, and further frighten those who are unsure, making them feel that they can’t ask any questions. It’s worth remembering that the first wave of the British anti-vaccination movement began in the 19th century in reaction to the Vaccination Act of 1853, which mandated smallpox inoculations for babies under three. Meanwhile, Johnson’s eye-catching focus on social media ignores the basic healthcare issues that are contributing to the fall.

The warping effect of anti-vaccination messaging on a very small minority of parents is clear—but there is little sign that their numbers are increasing. The potential danger they pose to public health and their own children should be manageable if “herd immunity” can be achieved, by making sure all other parents can and do vaccinate. In particular, this means engaging positively with, rather than alienating, the “fence-sitters.” If the department of health has full confidence in vaccines—as it should—then it should also be well placed to be persuasive without coming over as offensively bossy.

Australia now has a system which sends parents a text message straight after they take their child for a vaccination, which they can reply to with any possible side effects they observe. From one perspective, this could be seen as fuel for anti-vaccination myths. But, Leask believes, this sort of dialogue and transparency is essential to maintaining trust and keeping confidence in vaccination high. “We can’t just shut down all criticism of all vaccination programmes,” she says. “A vaccination programme or government should be confident enough that we can listen to people’s concerns.”