UK is late to the party in offering universal chickenpox vaccination – many other countries have been doing it for many years.
It is hard to understand the real reasons when haven’t done this sooner. It was partly due to a hypothesis about shingles.
The Herpes varicella-zoster virus causes chickenpox and then, later, shingles. Shingles is usually a late complication mostly affecting people aged over 60 – and the likelihood of sequelae like post-herpetic neuralgia increases with age. (It is not uncommon at earlier ages – I got it at 50 – but the burden of disease is more severe at older ages.)
The hypothesis used to explain not vaccinating children in the UK was that exposure of older people (previously infected) to children with chickenpox would provide “natural boosting” of their immunity to the virus, thereby delaying or preventing the onset of shingles disease. The evidence base for this being significant in reality has always, however, been poor and rather speculative.
Once shingles vaccine had been introduced, however, the shingles prevention hypothesis held even less water. I recall the director of vaccination in the Department of Health, at the time this vaccine was introduced, saying that it was only a matter of time before universal child vaccination would be offered.
Concerns about reigniting fears behind the millennial MMR scare were almost certainly part of the rationale for not introducing chickenpox vaccine sooner.
It seems extremely likely that the vaccine will not only prevent chickenpox, but also prevent or reduce shingles cases. But, while we believe that the live virus used in current chickenpox vaccines is unlikely to cause shingles – or much less commonly than wild virus – we cannot yet be certain of this (although data from countries which have been using the chickenpox vaccine is encouraging).
We now have an adjuvanted subunit shingles vaccine – which, not being a live virus vaccine can be given to the immune suppressed individuals who need it most. It is also more effective; and it may also be easier to produce (safely producing a live-virus vaccine is difficult). I can see no theoretical reason why this vaccine could not be reformulated as a paediatric chickenpox vaccine; and such a vaccine would have no conceivable risk of causing later shingles disease.
Re: Offer children chickenpox vaccine with MMR, JCVI recommends