Are Chickenpox Vaccinations Actually Harmful?

Written by Dr Clare Craig on March 9, 2026. Posted in Current News

In a recent Spectator article, “All Hail the Chickenpox Vaccine!”, Toby Young shares a harrowing personal experience involving his newborn son, poor care and a near‑fatal brush with chickenpox. It is a moving and powerful story

At the end of the piece, Young suggests that women of childbearing age who have not had chickenpox should consider getting vaccinated.

On this point, we are in full agreement. Targeted vaccination of non‑immune women before pregnancy directly addresses the rare but serious risks highlighted by his experience.

But this does not automatically justify a much broader policy change: adding the chickenpox vaccine to the routine childhood schedule, bundled into the MMR and given to every baby in the country.

It is odd, to say the least, that public health authorities, already struggling with trust in the MMR, would choose this moment to remove parental choice and raise the known risk of seizures.

When the UK adds the chickenpox vaccine to the routine childhood schedule this year, it will do something only one other country has done: it will offer the vaccine only as part of a combined MMR‑V injection, with no option for a separate MMR.

Luxembourg is the only country to not offer separate chickenpox and MMR, even in the United States and Germany, where the chickenpox vaccine is widely used, parents and doctors are still given the choice between MMR-V or separate injections.

There are measurable benefits from chickenpox vaccination but, as always, the risks are harder to measure and often go unmeasured such that assessing the risk benefit ratio is hard.

What are the benefits?

There are some measurable benefits to varicella vaccination, especially when looking at carefully selected endpoints. But the picture is incomplete, and important harms may be hidden.

Varicella‑zoster virus (VZV) which causes chickenpox enters through the respiratory tract. To prevent infection, as with other respiratory viruses, requires IgA antibodies on the mucosal surface.

The vaccine produces IgG in the blood. Protection against infection requires mucosal IgA. IgG does not reliably prevent infection. The consequence is that an infection in the lungs and even a pneumonia remain possible outcomes even though skin lesions and brain complications are much less likely.

We can compare rates in USA, which has vaccinated against chickenpox since 1995, with high uptake and the UK which does not.

1. Rates of chickenpox‑associated encephalitis are reduced

If skin lesions are not a part of post vaccine infection then mild cases will be missed. Severe cases could be missed too if testing is not done because of the absence of a rash. However, one measure, where testing has been done systematically, is encephalitis – or infection of the brain.

If serious infections were being prevented, we would expect rates of chickenpox‑associated meningoencephalitis (ME) to fall. A USA study showed a rate of about 0.2 percent among cases of ME (3 out of 1598) by contrast in the UK the rate was about five percent (10 out of 203).

This does suggest protection.

2. Reduced shingles in young people

Shingles results when dormant varicella-zoster virus that traveled from the skin to the nerves that supply it, is reactivated later in life. If a skin rash has been prevented on the first infection, then Shingles would reduce. Indeed, the rates in young people in USA have fallen.

3. Hospital admissions

The total number of hospital admissions for chickenpox in England is around 3,000 per year (including those without an overnight stay) which, for the whole population, works out at about 50 admissions per million.

There are around 1,400 hospital admissions per year in USA which works out at 4 per million per year. If England had US rates then about 2,700 chickenpox labelled hospital admissions could be saved. In the absence of systematic testing it is impossible to gauge the actual total because patients with no skin rash may not have been tested.

4. Deaths

Even with universal childhood chickenpox vaccination, the USA sees roughly the same number of chickenpox deaths per capita as England and Wales. The difference? Just 13 extra deaths in England and Wales over 10 years. Of course no one wants to see preventable deaths in children but there is no public health emergency here.

Figure 1: Chickenpox related deaths in children in USA and England and Wales

What are the risks?

Febrile seizures

Children receiving MMR‑V at 12–23 months have approximately one extra febrile seizure per 2,300 children vaccinated, compared to giving the same vaccines separately. Applied to the UK birth cohort (~600,000 births annually), that equates to approximately 260 seizure-related hospital admissions each year – a direct and measurable harm.

The chances are that the children affected by seizures would not be the ones who benefited from the intervention. Also, these are the excess compared to giving the drugs separately. Surely, we should “first, do no harm”?

Figure 2: CDC graph showing no increase in seizures with chickenpox vaccination alone but significant spike when MMR-V is given. Note the calculation only included the period up to 10 days despite continuing raised risk at that point.

Immune system

Furthermore, chickenpox is the only childhood illness many children will tackle and their immune systems need training in taking on a full disease. It protects against life long allergic conditions like atopic dermatitis.

Chickenpox may be the only full infectious disease many children acquire naturally. Eliminating it universally may have consequences for immune system development that we do not yet understand and fail to measure.

Possible increase in chickenpox and shingles in older people

Concerns have been raised that varicella immunisation will give less durable immunity than that provided by natural infection (essentially life-long) thus resulting in chickenpox in adult life, which is already known to be more severe than in childhood.

However, in heavily vaccinated countries the rates of chickenpox among adults has not increased.

It has also been suggested that childhood infections give an immunity boost to adults, which may act to reduce their risk of shingles. Studies from the US, Manitoba, Canada and Japan have looked at shingles incidence in the post-vaccination era compared to prevaccination, these studies showing a reduced incidence of shingles in the youngest age group (ie those who had been vaccinated themselves) but an increase in older age groups consistent with the loss of an immune boost.

A study from Ontario, however, showed no such increase. Herpes Zoster has been increasing in incidence in recent decades, in part related to demographic changes i.e. an aging population, which has made interpretation of these studies more difficult.

Given the long latent period for most cases of shingles, it will take decades before the real impact of universal childhood varicella immunisation will be known.

Conclusion: Do No Harm

The truth is that the benefit from adding chickenpox vaccination to MMR is not fully understood because there is no study systematically testing children to see if they have had rash free chickenpox.

Not testing could mean underdiagnosing chickenpox related deaths. That said the rates of encephalitis and shingles does reduce with vaccination. But there is a cost to pay in seizures, in hidden harms, and in the quiet erosion of parental trust.

The chickenpox vaccine doesn’t reliably prevent infection. It changes how chickenpox looks, how it is diagnosed, and how it is counted.

Public health officials often choose to weigh the many against the few. But medicine should have a positive benefit-risk ratio for individuals. When the benefits are uncertain and the harms are concrete, such as the 260 children each year in the UK expected to experience seizure-related hospitalisation following MMR-V, how many are too many?

Is there any good reason why the combined MMR-V vaccine has been chosen despite it being known to have double the risk of febrile seizures than using separate MMR and varicella? The only argument appears to be ‘convenience’ and ‘parental preference’.

Could you stand in front of a crowd of toddlers and select the 260 who will be harmed for a statistical gain?

If you cannot do it to individuals, you cannot justify it for the population.

Ethics that fail at the individual level fail altogether.

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Header image: Church Pharmacy

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