Why medical mistrust remains a great challenge in vaccination

Trust in the medical profession is crucial for maximal health benefit, for example, following medical advice, attending cancer screening, and adhering to treatment. However, in a recent article in The Lancet, Marcello Ienca et al claim that, across the world, trust in medicine has plummeted and is facing a historic crisis.

They describe what they call “the paradox of trust”, where “the very institutions that most rigorously develop and apply science are viewed as untrustworthy, politicised, or elitist. Meanwhile, uncredentialled and often unaccountable internet influencers with financial conflicts are increasingly trusted to interpret science”.

An example where trust in medicine is crucial for effectiveness is vaccination. This discovery has proved to be one of the greatest interventions in the history of medicine. It is a mainstay of disease prevention and the World Health Organization (WHO) estimates that, since 1974, vaccination has averted around 154 million deaths.

Despite the overwhelming evidence regarding the efficacy of vaccination, distrust of vaccination programmes has been steadily growing over the past 50 years and vaccine hesitancy has been declared by the WHO as one of the top ten threats to global health.

A hugely influential study that made a major contribution to the rise of the anti-vax movement was conducted in 1998 by Andrew Wakefield and reported in The Lancet. He falsely claimed a link between the MMR vaccine and autism in nine of the 12 children studied. The paper attracted huge media interest and scrutiny and was later identified as fraudulent and retracted. Despite this, the consequences of his research have been disastrous. The paper has been described as “perhaps the most damaging medical hoax of the 20th century”.

Suspicion about safety and a decline in MMR vaccination has continued, despite consistent refutations of the link with autism by major bodies, such the NHS in the UK and the Centers for Disease Control and Prevention (CDC) in the US. In 2024-25, only 84.4 per cent of UK children received both doses of the MMR vaccine – considerably below the 95 per cent required for herd immunity. The WHO reported that the UK had eradicated measles in 2017, however, in January 2026, confirmed that the UK had lost its measles-free certification.

Challenging anti-vaccination beliefs has proven no easy undertaking. Unfortunately, we seem to know more about how to increase vaccine hesitancy than how to reduce it.

A further challenge in promoting vaccination is that it suffers from what Marcello Ienca et al in their Lancet piece call the “invisibility paradox”.

The more successful medical interventions are at preventing disease, the more invisible their benefits become. This absence of evidence is misread as evidence of absence.

Commonly used interventions to reduce hesitancy such as myth debunking, employing scare tactics, and communicating certainty have limited efficacy. Furthermore, there is evidence that such interventions can provoke reactance in that they can paradoxically stiffen resolve and strengthen anti-vax attitudes. A major limitation of most studies in this area is that the primary outcome has almost always been vaccination attitudes or intention, rather than actual vaccination behaviour.

Behavioural scientists have known for many years that intention very often does not translate into behaviour – the well-recognised intention-behaviour gap. However, in January 2026, Matthew Whitaker et al published an important study of more than one million people in The Lancet. It was the first study that linked Covid vaccination attitudes before vaccination with subsequent vaccination behaviour.

Vaccine hesitancy is not a unitary phenomenon and the authors identified eight stable sub-categories of vaccine hesitancy, including concerns about effectiveness and side-effects, perception of low risk from Covid, mistrust of vaccine developers and fear of vaccines and reactions. Most hesitancy reduced over time following vaccine roll-out. Longitudinal analysis was conducted in the vaccine hesitant cohort and 65 per cent of those went on to receive one or more vaccinations. The most common categories of hesitancy, related to effectiveness and health concerns, declined substantially over the vaccine roll-out period and were not strongly associated with the likelihood of later vaccination.

However, those who were hesitant because of a generalised anti-vaccine sentiment, had low trust in vaccine developers or low perception of risk from Covid were particularly unlikely to change their minds and get vaccinated.

Whitaker et al concluded that most Covid vaccine hesitancy was “rooted in concrete concerns that can be addressed and successfully overcome with time and increasing availability of information”. However, we do not yet have convincing evidence from behavioural science as how to increase trust in vaccine developers, increase Covid risk perception and change general anti-vaccine sentiments.

Professor Ronan O’Carroll FRSE, Clinical and Health Psychologist and Emeritus Professor, the University of Stirling

This article originally appeared in ReSourcE Spring/Summer 2026.

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