Chickenpox vaccine claims: fact checked

In the wake of last month’s announcement that the NHS will offer the chickenpox vaccine to children across the UK next year, we’ve seen a number of false and misleading claims on social media.

Some social media users have responded to the news by incorrectly calling the vaccine “poison”, while others have suggested the campaign will involve an mRNA vaccine.

These claims are not correct. The chickenpox vaccine is not an mRNA vaccine, and while any vaccine may have some side effects, the chickenpox vaccine is not poisonous.

There is plenty of research which shows that chickenpox vaccines are safe, with one 22-year review of the vaccine which looked at 212 million doses being distributed worldwide finding the number of serious adverse events reported was just 0.8 per one million doses.

We’ve also seen claims on social media that the vaccine is pointless, as immunity can be gained by catching it as a child, when the disease is often mild. While it is true that immunity is gained through exposure, the vaccine’s use in other countries, like the US, has shown a significant decrease in chickenpox spread, hospitalisations and deaths.

The chickenpox vaccine is safe

The NHS describes vaccines in general as “the most effective way to prevent many infectious diseases”.

Vaccines can cause mild side effects, such as swelling or pain at the injection site, which might worry some people, but the NHS notes that most are “mild and do not last long”.

When it comes to the chickenpox vaccination in particular, multiple studies have shown that it is safe. It has been used in the USA for decades, and has been associated with a 97% reduction in chickenpox cases.

The NHS notes that side effects of the chickenpox vaccine can include a high temperature, a rash in the area where the injection was given and pain where the injection was given.

The NHS adds that “more serious side effects, such as a severe allergic reaction, are very rare”, and adds that staff giving the vaccine are trained to treat this immediately.

Medical practitioners and members of the public are also able to report their own suspected side effects of a vaccination to the MHRA via the Yellow Card scheme.

The chickenpox vaccine is not an mRNA vaccine

Contrary to some claims we’ve seen circulating, the chicken pox vaccine isn’t an mRNA vaccine at all.

Both the Varilrix chickenpox vaccine and Varivax chickenpox vaccine—the two vaccines available in the UK—are live attenuated vaccines.

The key difference is that a live attenuated vaccine uses a weakened version of the virus it intends to protect against. By contrast, an mRNA vaccine contains instructions that tell your body to create a harmless piece of the virus, which it then learns to attack if you become infected with the real thing.

Claims that mRNA vaccines are poisonous or harmful are common, particularly when it comes to Covid vaccines, and we’ve written about this before.

What is the point of the chickenpox vaccine?

We’ve also seen some confusion as to why the vaccine is needed in the first place. Many social media users have rightly pointed out that the disease is often mild in children. They also claim that immunity can be gained by deliberately catching it, referring to trends like ‘chickenpox parties’ (which are strongly discouraged by doctors and some health bodies).

It’s true that immunity is typically gained through exposure and that the resulting infection is generally mild. But that doesn’t mean the vaccine is pointless.

For one thing, it cuts out unnecessary infections. Although often mild, chickenpox can cause complications. A child might develop a secondary bacterial infection, such as impetigo and cellulitis, and, in more extreme cases, neurological complications such as Reye's syndrome.

If you had chickenpox as a child, you will likely have developed an immunity to the virus and so are very unlikely to get it again. Yet if you didn’t catch it as a child and don’t have immunity as an adult, chickenpox can be much more serious, with 80% of deaths related to chickenpox in England and Wales occurring in those who get it when they’re older. Complications in adults include pneumonia and hepatitis.

And if someone who is pregnant catches chickenpox, they can develop pneumonia, with the severity increasing the later in the pregnancy it occurs. Newborns can also develop shingles in infancy or early childhood if the mother’s infection occurs at 20 to 37 weeks of pregnancy.

The vaccine helps reduce these risks in a way that “chickenpox parties” can’t: that is, by reducing the prevalence of the virus in the population, and preventing severe cases which may have resulted in complications or hospitalisation.

Why is the chickenpox vaccine being rolled out now?

While the chickenpox vaccine has long been offered to certain vulnerable groups, this marks the first time it will be part of the routine NHS childhood immunisation schedule in each of the four UK nations.

In 2009, the Joint Committee on Vaccination and Immunisation (JCVI) declined not to recommend a vaccination programme because modelling suggested it wouldn’t be cost effective until 80 to 100 years after it started. This is because it was hypothesised that cases of shingles—which is a disease caused by the same virus as chickenpox, varicella zoster virus—could increase in middle-aged adults, who rely on natural exposure to keep their immunity strong.

The JCVI reviewed this guidance again in November 2023, and found that these concerns about a rise in shingles cases were based on an incorrect overestimate of how immunity boosting worked. Examples of chickenpox vaccine programmes in other countries also indicated no such outbreaks occurred. The Committee therefore recommended the jab be introduced as part of the routine childhood schedule.

Vaccine misinformation can cause direct damage to people’s physical or psychological health, and can put particular communities and vaccine coverage levels at risk.

If it spreads at scale it can introduce confusion about the causes and treatments of illnesses, create distrust of medical professionals, and distract from or undermine medical consensus and public health messaging.