The chickenpox vaccine is not part of the routine UK childhood vaccination programme because chickenpox is usually a mild illness, particularly in children.

There's also a worry that introducing chickenpox vaccination for all children could increase the risk of chickenpox and shingles in adults.

Chickenpox in adults

In adults, chickenpox tends to be more severe and the risk of complications increases with age.

If a childhood chickenpox vaccination programme was introduced, people would not catch chickenpox as children because the infection would no longer circulate in areas where the majority of children had been vaccinated.

This would leave unvaccinated children susceptible to contracting chickenpox as adults, when they are more likely to get a more serious infection, or in pregnancy, where there is a risk of the infection harming the baby.

Shingles in adults

We could also see a significant increase in cases of shingles in adults [n.r. as it already happened in the US].

Being exposed to chickenpox as an adult – for example, through contact with infected children – boosts your immunity to shingles.

If you vaccinate children against chickenpox, you lose this natural boosting, so immunity in adults will drop and more shingles cases will occur.

Source: NHS.uk (excerpt) — The NHS website is the UK's biggest health website with more than 43 million visits per month. We strive to be a world-leading health information service putting people at the heart of everything we do. The website is funded by the Department of Health and Social Care (DHSC).