This post was inspired by a conversation in an email discussion list run by the British Interactive Group (BIG), the skills sharing network for individuals involved in the communication of science, technology, engineering and maths subjects.
I was 10 days old when I got chickenpox – my brother gave it me as a “welcome to the world” present, and I’m told I developed three spots around my face. But as far as I’m aware, I’ve suffered no long-term consequences, aside from a perfectly round scar above my eyebrow. Many people’s experiences of chickenpox are equally forgettable, developing it in their early years of childhood – it’s itchy and annoying, but rarely lasts more than a week.
However, chickenpox in adulthood can cause more problems – with potential risks such as bacterial infections on the skin, in the lungs, or in rare cases the brain and nerves. People with compromised immune system, such as people with HIV, or patients taking steroid treatments or chemotherapy, are particularly at risk. For pregnant women, chickenpox can sometimes cause problems for their unborn child.
Another potential complication of chickenpox is shingles, which affects between a quarter and a third of people who have previously had chickenpox. The varicella zoster virus which causes chickenpox hides and hibernates inside the nerve cells, to be awakened decades later for reasons that aren’t entirely clear. Shingles has many of the same hallmarks as chickenpox, such a fever and red itchy rash – but can last for weeks. There can be some long-term consequences, including severe pain that can last for weeks or sometimes months. And rarely, it can cause numbness and pain for many years after the rash has cleared up.
Chickenpox, vaccines, and parties
The two chickenpox vaccines available are ‘attenuated’ live vaccines – a small dose of a weakened varicella zoster virus. Two doses of varicella vaccine gives a child a 98% chance of avoiding chickenpox, and the vaccines are safe and well-tolerated.
Before the vaccines, there were “pox parties” – where children were encouraged to play with kids who had chickenpox so that they developed it early. Some members of BIG remember them well:
“I’m old enough to have got my immunity to chickenpox from being sent to play with the first kid down the street to get it. I can’t remember much other than itchy spots and don’t know of anyone who suffered any more than that.”
“I was also subject to the pox party – it led to some time off school but bad itching that had to be controlled with an ocean of Calamine lotion… some kids did suffer with scabs and small scars after if they scratched away.”
A double-edged sword
So there’s a safe, effective vaccine for a common childhood illness which could have serious complications for some people. But why isn’t it part of the childhood vaccination programme in the UK?
The Joint Committee on Vaccination and Immunisation (JCVI), which advises the UK government, concluded in 2010 that introducing a universal chickenpox vaccination programme would, in the short-to-medium term, actually increase the number of cases of shingles, and possibly adult chickenpox.
1) An increase in shingles
Firstly, remember that you can only develop shingles if you have already developed chickenpox – because shingles is basically your chickenpox coming back in later life.
If you’ve had chickenpox, every time you come into contact with someone else with chickenpox, not only does the immune system remember it (so you don’t get chickenpox again) but it gives your immune system a little boost. It appears that this regular contact with chickenpox throughout life helps keep shingles at bay – one study suggests adults who live with kids (e.g. their children or grandchildren) have a 25% lower risk of developing shingles in their lifetime.
But if a vaccination programme is brought in, there’ll be fewer kids with chickenpox to give adults this boost to their immune system – which will mean more adults will develop shingles in later life.
Eventually, thanks to the childhood vaccination programme, there’ll be so few people who develop chickenpox anyway that very few adults could ever develop shingles. But that could take a long time – one analysis suggested an uplift in shingles cases could last for between 30 and 50 years after the introduction of a chickenpox vaccination programme – mostly in the middle-aged, who aren’t covered by the existing shingles vaccination programme for the over 70s.
2) A possible increase in adult chickenpox
Another suggestion from the JCVI was the possibility of an increase in adult cases of chickenpox.
Imagine you’re a young child who hasn’t had chickenpox. Currently, roughly 90% of people who get chickenpox are children like you, under the age of 14. Chickenpox is very contagious, so the chances of you making it through childhood and not contracting it are slim.
Now let’s say there’s a widespread vaccination programme against chickenpox – not every child will be vaccinated initially, but most will – the JCVI estimate that 70-80% being vaccinated should be achievable. And let’s say you don’t get vaccinated, for whatever reason. Now that fewer of your fellow kids develop chickenpox, the chances that you, an unvaccinated child, will make it through to adulthood without getting chickenpox are now much higher. You probably will catch it eventually, but it’s now more likely that it’ll be when you’re an adult – when the complications from the disease can be more serious.
Eventually, as more children are vaccinated, the risk faced by the unvaccinated will decrease (so-called “herd immunity”), as the chances of coming into contact with someone with chickenpox becomes vanishingly small – and so this initial uplift will subside.
No vaccination programme for now
So is a vaccination programme worth it? In the long-term, yes. But it could take as many as 100 years for any widespread vaccination programme against chickenpox to become cost-effective – and during that time you’ll see an increase in shingles and possibly adult chickenpox.
Ultimately, chickenpox is, for the majority of people, a mild disease. Sure, anyone can pay privately for a vaccine to prevent the disease for themselves or their child. But is it worth spending public money on a widespread vaccination programme to eradicate it entirely? Possibly not – at least that’s the judgement made by the NHS here in the UK.
The chickenpox vaccine is only routinely available to people in regular contact with someone at risk of developing severe complications.
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Thank you to the British Interactive Group’s BIG-chat email list for the interesting discussion that led to this blog, and to NHS Choices for help with providing references. More information and further reading:
- NHS Choices – Chickenpox vaccine: FAQs
- “Green book” chapter on Varicella (pdf) – The Green Book is Public Health England’s advice on immunisation against infectious diseases.
- Joint Committee on Vaccination and Immunisation (JCVI) statement (pdf) on varicella and herpes zoster vaccines.