In her professional life, Sophia Newcomer analyses vaccination trends and safety in the United States. The epidemiologist, at the University of Montana, Missoula, has investigated the factors that stop some people from completing their children’s recommended immunizations.
So it’s no surprise that in her personal life, Newcomer is asked questions about vaccines, too. “I’m a mom — I’ve had plenty of playground conversations,” she says. “When people find out I study vaccines, they love to ask questions. What I try to do is listen and, as best as I can, share what I know.”
Questions and doubts about vaccines are on the rise worldwide. A major global study found that perceptions of vaccines’ importance for children dropped in 52 of 55 countries studied during the COVID-19 pandemic1 (see ‘Lost confidence’). In the United States, about 20% of parents are hesitant about vaccines — one reason for an outbreak of measles this year that has killed three unvaccinated people.
Public-health specialists worry that these trends could worsen, in part because of the influence of Robert F. Kennedy Jr, who has repeatedly questioned the safety of vaccines and inaccurately connected them to autism. Kennedy was tapped this year by US President Donald Trump to lead the Department of Health and Human Services (HHS), which approves vaccines and makes recommendations about their use.
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The shift in public attitudes towards immunizations can leave scientists, physicians and many others feeling disheartened because vaccines are among the most cost-effective ways to prevent disease and have saved more than 150 million lives over the past 50 years. So what should you say to someone who has doubts? What kind of information or argument might help when talking to family or friends? Fortunately, a surge of research on vaccine hesitancy over the past decade is starting to offer some answers. “There is a lot that we can draw from,” says Heidi Larson, who studies confidence in vaccines at the London School of Hygiene & Tropical Medicine.
Researchers say that anyone can help to address vaccine hesitancy by listening to concerns and offering positive opinions. “If you think vaccination is a good idea, if you trust that, if you think it’s a good way to protect your children, I think you can share that view,” says Daphne Bussink-Voorend, who studies vaccine decisions at Radboud University Medical Centre in Nijmegen, the Netherlands.
Listen, do not judge
The first thing to do if someone expresses uncertainty about vaccines to you, say researchers, is not to judge or dismiss them. It’s wrong to assume that people are ignorant, irrational or have naively swallowed online misinformation. A lot of people have genuine and legitimate questions and “you’re going to lose them if you immediately jump back and say ‘that’s silly’ or ‘that’s not the fact’”, Larson says. (Researchers distinguish between vaccine hesitancy — being unsure about vaccination — and ‘anti-vaccine’ activists who campaign against it.)
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Instead, researchers agree, it’s best to actively listen, ask questions and be curious about what’s behind the concerns. “I think that is sometimes difficult, but we should really be open to people’s views and ideas,” says Bussink-Voorend. “Once we know what the issues are, what specific barriers are, then we can address them, one by one,” says Mohammad Sharif Razai, a public-health researcher at the University of Cambridge, UK.
Researchers have identified a wide range of reasons that people hesitate about getting themselves or their children vaccinated. In 2014, an expert working group on vaccine hesitancy convened by the World Health Organization supported grouping these reasons into three buckets: confidence (I don’t trust the safety and effectiveness of vaccines, or the health system delivering them); complacency (I don’t need it because the risks are low); and convenience (I can’t access it easily)2. Context is also important, because people’s culture and religious or ethnic background can influence their attitudes.
One major European study pointed to the root of many concerns. The study, called VAX-TRUST, examined why parents hesitated to vaccinate their children in seven European countries between 2021 and 2024, a period that spanned the COVID-19 pandemic3. Typically, hesitancy “starts with personal concerns about, ‘what will this do to my child? How will it affect my health?’”, says Pia Vuolanto, a social scientist at Tampere University in Finland, who led the study.
Particularly influential in seeding those doubts, Vuolanto says, were anecdotal stories from friends and in the media that involved possible vaccine side effects. “Previous cases were very important in shaping their views,” she says — even though serious side effects are rare and data show that, for most people, the benefits of vaccines outweigh the risks.
A child is vaccinated against measles, mumps and rubella in Papua New Guinea.Credit: Kate Holt/eyevine
A review published in 2023 measured the lasting damage one scare story can cause. The authors assessed 115 studies examining why parents in the United States hesitate over the childhood measles, mumps and rubella (MMR) vaccine4. The most common reason was fear of triggering autism, which stems partly from a prominent 1998 paper in the Lancet that claimed to show a link between the MMR vaccine and autism. The paper was found to be fraudulent and was retracted, and subsequent studies have convincingly shown that no link exists, although Kennedy and others continue to draw connections. A spokesperson at the HHS says that the US National Institutes of Health is actively investigating the root causes of autism, and is confronting the issue of rising autism rates “employing only gold-standard, evidence-based science”.
The HHS spokesperson added that “blaming Secretary Kennedy for vaccine hesitancy ignores a broader and more complex reality: trust in public-health institutions declined during the COVID-19 pandemic, driven in large part by inconsistent messaging, shifting mandates and the failure to provide transparent, long-term safety and efficacy data”.
Express your view
It might sound obvious, but researchers say that it’s important in a conversation to provide information or opinions. “You need to elicit the concerns and then share accurate, reliable information,” Razai says.
Physicians and other health-care workers are best placed to provide that advice. A 2023 systematic review of studies, including 15 randomized trials, found that consistent, clear recommendations from trusted health-care professionals that addressed misconceptions and noted benefits were strongly associated with increased vaccination during pregnancy, particularly when the recommendations were delivered face-to-face5. It’s “one of the most important evidence-based strategies”, says Razai, who led the review. But the goal, he stresses, should be enabling someone to make their own informed decision, not telling them what to do. “I think that’s a really effective way of gaining people’s trust.”
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One method of doing this in a non-judgemental way is called ‘motivational interviewing’. This involves an empathetic, respectful conversation between a health-care worker and a prospective vaccine recipient that aims to strengthen their motivation. It typically starts with a recommendation to vaccinate, but if someone expresses ambivalence or reluctance, a health worker might ask ‘Why are you unsure?’, then acknowledge the concerns and offer information tailored to address them6.
If a parent expresses worry about the MMR vaccine and autism, for example, the health worker might say: ‘More than 500 studies around the world have demonstrated that there is no link between the vaccine and autism. The frequency of autism is the same in vaccinated children as it is in non-vaccinated children. What do you think?’ (This compares with a more didactic approach of: ‘The vaccine is safe, I assure you’ or ‘You should update your child’s vaccinations’.)
Several studies have suggested that motivational interviewing can change behaviour. In one trial in Quebec, Canada, parents of around 1,100 babies received a session using motivational interviewing on the maternity ward after their children were born7. Seven months later, 76% of children in the experimental group had received all the recommended vaccines, compared with 69% in a control group that did not receive the intervention. This and other results convinced the government in Quebec to roll out the programme to all parents of newborns, starting in 2017. The programme led to a nearly 7% increase in vaccination coverage after 24 months.
People who are not health professionals can share such messages, too, researchers say — they don’t have to know detailed facts and figures from studies. It also helps to get personal. “For those who are just a little bit unsure, often sharing your personal experience of why you vaccinated, why you trust vaccines, is enough,” says Vuolanto.
Be honest
Transparency and acknowledging uncertainties is key, researchers say. A systematic review8 of methods for combating vaccine misinformation in 2023 found that communicating with certainty, rather than recognizing that there are unknowns about risks or effectiveness, could backfire. Communicating the weight of evidence and scientific consensus about vaccines seemed more promising.
