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RSV, Guillain-Barré Syndrome and the Psychology of Rare Risks

July 2026

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One of the most interesting things about working in immunisation isn't the vaccines themselves: it's how our brains interpret risk.

Take the recent discussions around RSV vaccination and the rare risk of Guillain-Barré syndrome (GBS). Since the MHRA issued its safety update, I've heard many clinicians on courses asking, "How do I mention this without frightening patients?" It's a fair question, because the psychology of risk communication matters just as much as the science. So, as it's a common query it's time for another blog!

Let's start with the facts.

The MHRA has advised that there is a small increased risk of GBS following the RSV vaccines Abrysvo and Arexvy in adults aged 60 years and over. Importantly, the Commission on Human Medicines concluded that the benefits of vaccination continue to outweigh this very small risk. Healthcare professionals are advised simply to inform patients about the symptoms of GBS and encourage them to seek medical attention promptly if they develop them. This isn't a withdrawal of the vaccine or a change in recommendation. It's an example of a safety monitoring system working exactly as it should.

The numbers deserve some perspective.

UK surveillance identified 21 reports of GBS following approximately 1.8 million RSV vaccine doses administered to older adults. That equates to roughly one reported case for every 85,000 doses, or around 0.001% of vaccinations. Not every reported case is necessarily caused by the vaccine, but the available evidence suggests there is a genuine, albeit very small, increase in risk in this age group.

It's equally important to recognise what the evidence doesn't show.

To date, there is no evidence of an increased risk of GBS following maternal RSV vaccination during pregnancy. The signal has been observed only in older adults receiving RSV vaccination, and current UK recommendations remain unchanged for both older adults and pregnant women.

So why do patients often become disproportionately worried?

Psychologists describe something called the 'availability heuristic'. Basically, our brains judge how likely something is by how easily we can imagine or remember it. A dramatic condition like GBS is emotionally powerful. Once we've heard about it, it becomes memorable, and memorable events feel common even when they are exceptionally rare.

There's also probability neglect. We naturally focus on what might happen rather than how likely it is to happen. Mention the word "paralysis" and many people stop processing the tiny probability attached to it.

As clinicians, our role isn't to minimise the risk, but neither should we accidentally magnify it.

One of the most balanced ways to frame the conversation is to acknowledge the risk honestly before placing it into context.

For example:

"Like all medicines, RSV vaccines are monitored very closely. Researchers have identified a very small increase in the risk of Guillain-Barré syndrome in older adults after vaccination. It remains a very rare event, and the MHRA continues to advise that, for eligible adults, the benefits of preventing severe RSV disease outweigh this small potential risk."

This approach respects informed consent while avoiding unnecessary alarm.

Risk never exists in isolation. Older adults are offered RSV vaccination because RSV itself can lead to pneumonia, hospital admission and death. Every healthcare decision involves balancing risks against benefits, and in this case the UK's independent experts (like our wonderful JCVI committee) continue to conclude that vaccination offers substantially greater protection than harm for those eligible.

Perhaps the biggest lesson isn't about RSV at all. It's about recognising that our patients don't assess risk like statisticians. They assess it like human beings. Understanding a little psychology can help us communicate the science with greater clarity, compassion and confidence.

Putting it into practice: conversations you might have in clinic

Here are a few examples of how you might answer some of the questions patients ask. There isn't a single "correct" script as every patient is different. But the aim is to be honest, balanced and reassuring without dismissing the patient's concerns.

Patient: "What is Guillain-Barré syndrome?"

Clinician: "Guillain-Barré syndrome, or GBS, is a rare condition where the body's immune system mistakenly attacks the nerves. It usually starts with tingling or weakness in the feet or legs, which can spread upwards. Most people recover, although it can take weeks or months, and some people need treatment in hospital. It is a recognised but very uncommon condition that can occur after a range of infections, and very occasionally after some vaccines."

Patient: "How likely is it that I'll get it from this vaccine?"

Clinician: "Based on the UK safety data so far, around 21 reports were identified after approximately 1.8 million RSV vaccine doses were given to older adults. That works out at roughly one report for every 85,000 doses. So if there is an increased risk, it is very small. The reason we know about it at all is because our vaccine safety monitoring systems are designed to detect even very rare events."

Patient: "So why are you recommending it if there's a risk?"

Clinician: "That's a really sensible question. Every medicine and every vaccine has potential risks as well as benefits. The reason the NHS and independent experts continue to recommend the RSV vaccine is because, for people in the eligible age groups, the protection against severe RSV illness, hospitalisation and its complications is considered much greater than this very small potential risk."

Patient: "Could I get GBS from catching RSV instead?"

Clinician: "Yes. GBS is known to occur after a number of infections, including respiratory and gastrointestinal infections. So when we think about vaccination, we're not comparing a small vaccine risk with 'no risk', we're comparing it with the risks that come from the infection itself, as well as the risk of becoming seriously unwell with RSV."

Patient: "Has this happened in pregnant women having the RSV vaccine?"

Clinician: "No. The safety signal identified so far has been in older adults receiving RSV vaccination. Current evidence has not shown an increased risk following RSV vaccination during pregnancy, and the recommendations for pregnant women remain unchanged."

Patient: "Should I be worried?"

Clinician: "I don't think worried is the right word, I think informed is. We talk about these rare side effects because we want you to have all the information you need to make your decision, and to be able to act quickly if something were to go wrong. The vast majority of people who receive the RSV vaccine have no serious problems at all, and the benefits are still considered to outweigh this very small risk."

Patient: "What symptoms should I look out for?"

Clinician: "If, in the weeks after vaccination, you developed symptoms such as tingling in your hands or feet, weakness that seems to be getting worse, difficulty walking, or weakness spreading up your body, you should seek medical attention promptly. These symptoms are very uncommon, but it's important that they're assessed quickly if they do occur."

Ultimately, good risk communication isn't about persuading someone to have a vaccine. It's about helping them understand both the benefits and the risks in a way that is accurate, proportionate and meaningful. If we understand a little about how people naturally think about risk, we can have conversations that are not only scientifically correct, but also compassionate, balanced and genuinely supportive of informed consent.

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