Easy-to-read medicine information about chickenpox vaccine – what it is, when is it given and possible side effects.
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Note: There is another varicella vaccine called Zostavax®. This is to protect against shingles, and is not to be given to children.
What is chickenpox vaccine?
Chickenpox vaccine protects against infection from the varicella zoster virus, which causes chickenpox infection. The virus is easily spread by sneezing and coughing, or by contact with weeping chickenpox blisters. You can even catch the chickenpox virus from touching clothing or other objects that have fluid from the blister on them.
The chickenpox vaccine is a live vaccine which is made using chickenpox viruses that have been weakened (or attenuated), before being included in the vaccine. After immunisation, the weakened vaccine viruses replicate (grow) inside you. This means a very small dose of virus is given to stimulate a response by your immune system. Live attenuated vaccines do not usually cause disease in vaccinated people who have a healthy immune system. When a live attenuated vaccine does cause any illness, it is usually milder than if you had caught the disease. Live attenuated vaccines given by injection are generally effective after one dose.
Why is immunisation against chickenpox important?
In most people, chickenpox is a mild disease that doesn't cause any lasting problems. Around 1 in 20 healthy children develop a bacterial skin infection from chickenpox, that will need antibiotic medicine. Untreated bacterial skin infections can lead to bacterial infection in other parts of your body, including pneumonia and blood stream infection (septicaemia). Other complications of chickenpox are rare and include encephalitis (brain inflammation) and inflammation of your joints, kidneys and liver.
Chickenpox tends to be more severe in adolescents and adults, pregnant women and their unborn babies and people of any age with poorly functioning immune systems. Read more about chickenpox.
Chickenpox during pregnancy can spread to your baby. The highest risk is during the first 20 weeks of pregnancy. Up to 2 in 100 infants exposed to chickenpox before birth will be born with congenital varicella syndrome and may have skin scarring, eye, limb and brain abnormalities, developmental delay and a poor outcome. Up to 30 in 100 newborn babies with chickenpox develop severe disease that can result in death.
Pregnant women should not be given the chickenpox vaccine. The vaccine’s safety in the unborn baby has not yet been demonstrated, although no harmful effects have been described following inadvertent administration to pregnant women. When you get immunised, you should avoid getting pregnant for at least 1 month afterwards. If you'ree planning a pregnancy, check in early with your midwife or doctor to see whether you need to be immunised against chickenpox.
Who should be immunised against chickenpox?
Chickenpox immunisation is recommended and funded in New Zealand for the following groups:
- children turning 15 months of age
- children turning 11 years of age who have never been infected with or previously immunised against chickenpox.
People with a weakened immune system are at high risk, but may not be able to have the vaccination themselves, so close contacts of these people are recommended to be vaccinated. The vaccine is funded for certain high-risk individuals and/or their close contacts.
Chickenpox immunisation is also recommended, but not funded, for:
- teenagers and adults who have never been infected with or immunised against chickenpox
- women who are planning a pregnancy and have never been infected with or immunised against chickenpox
- people who are not immune to chickenpox and who are working in professions where they come into contact with young children
- parents who have not had chickenpox.
Who should NOT be immunised against chickenpox?
Since the chickenpox vaccine is a live vaccine. This means that it can cause chickenpox (although it is usually milder) and it should not be used if:
- you are pregnant
- you have active untreated TB (tuberculosis)
- you are taking high dose steroids such as prednisone or dexamethasone.
How effective is the chickenpox vaccine?
A single chickenpox vaccine dose provides about 99% protection against severe disease and 80% protection against chickenpox infection of any severity. It is still possible to get chickenpox after having the vaccine, but the infection is usually mild.
How is the chickenpox vaccine given?
The chickenpox vaccine is given as a subcutaneous injection (injected under your skin). It is usually given as one dose, but 2 doses may be recommended for some people.
Possible side effects
Like all medicines, vaccines can cause side effects, although not everyone gets them.
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The following links provide further information on chickenpox vaccines:
- Chickenpox Immunisation handbook, NZ 2017
- Tips following immunisation Ministry of Health, New Zealand
- Immunise against chickenpox HealthEd, New Zealand, 2017