The chickenpox (varicella) vaccine provides protection against the varicella zoster virus that causes chickenpox.
The chickenpox vaccine is not part of the routine childhood vaccination schedule. The vaccine is currently only offered to people who are particularly vulnerable to chickenpox.
The vaccine does not contain thiomersal (mercury).
The vaccine consists of two doses which should be given 4 to 8 weeks apart
Groups at risk from chickenpox
Chickenpox is a common childhood infection. In most cases the symptoms are mild and complications are rare. Almost all children develop immunity to chickenpox after infection, so only catch it once. The disease can be more severe in adults.
Certain groups of people are at greater risk of serious complications from chickenpox. These include people who have weakened immune systems through illness, such as HIV, or through treatment, such as chemotherapy.
Chickenpox can be very serious for an unborn baby when a pregnant woman catches the infection. It can cause a range of serious birth defects as well as severe disease in the baby when it is born.
How the vaccine works
The chickenpox vaccine contains a small amount of the live weakened varicella zoster virus.
The vaccine causes your immune system to produce antibodies that will help protect against chickenpox.
The vaccine is recommended for individuals who are likely to come into contact with people in the 'at-risk' groups. This is to reduce the risk of the individuals spreading the infection to those at risk.
For example, if you were having chemotherapy treatment, it would be recommended that non-immune children be given the chickenpox vaccination. Or if you were about to start work in a radiotherapy department and you had no previous history of chickenpox, the vaccine would be recommended.
How effective is the vaccine ?
It has been shown that 9 out of 10 children vaccinated with a single dose will develop immunity against chickenpox. A two-dose schedule is now recommended for all, as it gives a better immune response.
Three-quarters of teenagers and adults who are vaccinated with two doses will develop immunity against chickenpox.
The most common side effect of the chickenpox vaccine is soreness and redness around the site of the injection.
This side effect develops in around one in five children and one in four teenagers and adults.
A mild rash may occur in 1 in 10 children and 1 in 20 adults.
Serious side effects, such as anaphylaxis (a serious allergic reaction), are rare. They occur in less than 1 in 100,000 vaccination cases.
Though the varicella vaccine is not part of the routine childhood immunisation schedule it is in other countries, such as the US and Germany.
Millions of doses of the vaccine have been given and there is no evidence of any increased risk of developing a long-term health condition as a result of the vaccination.