Chickenpox (Varicella) Vaccine

Key vaccine facts

This vaccine gives protection against chickenpox infection. For those who are vaccinated but still get chickenpox, the symptoms will generally be milder.

The vaccine contains a live strain of the varicella-zoster (chickenpox) virus which has been weakened (attenuated). This stimulates the immune system but does not cause disease in healthy people. However, the chickenpox vaccine should not be given to people who are clinically immunosuppressed (see below).

Two brands of chickenpox vaccine are used in the UK: Varilrix (see the Patient Information Leaflet) and Varivax (see the Patient Information Leaflet).

Who should have the vaccine?

In the UK the chickenpox vaccine is not currently part of the routine childhood schedule. It is recommended for those in close contact with people who are particularly at risk of complications from chickenpox. This includes:

Healthcare workers of all kinds who are not immune to chickenpox
Healthy family members and contacts of people without a fully-working immune system (for example, those with HIV, those without a spleen, people who have had an organ transplant, and those receiving chemotherapy treatment). As the chickenpox vaccine is a live vaccine, people without a fully-working immune system cannot receive the vaccine themselves.

The vaccine is also available for laboratory workers who are not immune to chickenpox and who may come into contact with the virus as part of their job.

In the UK the vaccine is given to adults and children over the age of one year. Two doses are given, at least 4 weeks apart. The exact spacing between doses depends on the brand of vaccine given and the age of the person receiving the vaccine.

Who should not have the vaccine?

The chickenpox vaccine should not be given to people who are clinically immunosuppressed (either due to drug treatment or underlying illness). This is because the vaccine strain could replicate too much and cause a serious infection. This includes babies whose mothers have had immunosuppressive treatment while they were pregnant or breastfeeding. For more information see the MHRA's Drug Safety Update (April 2016).

The chickenpox vaccine is not recommended for pregnant women as a matter of caution. However, studies have not shown any link between the weakened virus in the vaccine and any specific problems in babies born to women who received a chickenpox vaccine while they were pregnant. See 'Is the vaccine safe?' below.

What protection does the vaccine give?

Two doses of the vaccine give about 98% protection in children and about 75% protection in teenagers and adults.

Ingredients

The chickenpox vaccines used in the UK are called Varilrix and Varivax. Apart from the active ingredients (the antigens), the vaccines may contain very small amounts of these added ingredients:

highly purified gelatine, used as a stabiliser (Varivax only - there is no gelatine in Varilrix)
sorbitol, mannitol, lactose or urea, safe organic compounds used as stabilisers

The vaccines may also contain traces of these products used during the manufacturing process:

neomycin, an antibiotic used to stop bacteria growing and contaminating the vaccine
harmless salts based on sodium and potassium, used as acidity regulators

Growing the active ingredients for the vaccine:

The virus strain used in both vaccines is grown in the laboratory using human cell strains

Other brands of chickenpox vaccine used in other countries may contain different ingredients. If you are not in the UK, ask for the Patient Information leaflet for the vaccine you are offered.

Side effects

The frequency and type of side effects are slightly different for the two chickenpox vaccines used in the UK. For full information on side effects, ask for the Patient Information leaflet for the vaccine you are offered. As a general guide, side effects may be experienced as listed below.

Very common (affecting more than 1 in 10 people at each dose):

reactions at the site of the injection, including redness, pain and swelling.
raised temperature (fever)

Common (affecting up to 1 in 10 people at each dose):

chickenpox-like rash (in up to 10% of adults and 5% of children)
mild cold-like symptoms
irritability
itching at the injection site

Uncommon (affecting up to 1 in 100 people at each dose):

swollen glands, headache, sore throat, cough, or runny nose
feeling sick or being sick
diarrhoea
a rash with blisters
joint or muscle pain
very high temperature
drowsiness, tiredness, or feeling generally unwell

For rarer side effects (affecting fewer than 1 in 1000 people), see the Patient Information Leaflets for Varivax and Varilrix.

Anaphylaxis

As with any vaccine, medicine or food, there is a very small chance of a severe allergic reaction (anaphylaxis). Anaphylaxis is different from less severe allergic reactions because it causes life-threatening breathing and/or circulation problems. It is always extremely serious but can be treated with adrenaline. Health care workers who give vaccines know how to do this. In the UK between 1997 and 2003 there were a total of 130 reports of anaphylaxis following ALL immunisations. Around 117 million doses of vaccines were given in the UK during this period. This means that the overall rate of anaphylaxis is around 1 in 900,000.

More information on side effects

Reactions listed under ‘possible side effects’ or ‘adverse events’ on vaccine product information sheets may not all be directly linked to the vaccine. See Vaccine side effects and adverse reactions for more information on why this is the case.

If you are concerned about any reactions that occur after vaccination, consult your doctor. In the UK you can report suspected vaccine side effects to the Medicines and Healthcare products Regulatory Agency (MHRA) through the Yellow Card Scheme. You can also contact the MHRA to ask for data on Yellow Card reports for individual vaccines. See more information on the Yellow Card scheme and monitoring of vaccine safety.

More information about the vaccine

A treatment called human varicella zoster immunoglobulin (VZIG) is given to people in risk groups who have been exposed to chickenpox. Immunoglobulins are special concentrated antibody preparations which provide immediate short-term protection against disease. VZIG can help to reduce the severity of chickenpox symptoms for some people in risk groups.

The chickenpox vaccine currently available in the UK is a single vaccine. However, several countries use the MMRV vaccine, which combines the MMR (measles, mumps and rubella) vaccine with a varicella (chickenpox) vaccine. This vaccine is given routinely in the USA, Germany and Australia. For children aged two and younger, studies have shown that more of them develop fever after the MMRV vaccine, compared with giving the MMR vaccine and the chickenpox vaccine separately on the same day. In particular there is an increased risk of febrile convulsions (fits). These occur 7 to 10 days after MMRV vaccination.

The Joint Committee on Vaccination and Immunisation (JCVI), which advises the UK Government, has so far advised that it would not be cost effective to introduce the chickenpox vaccine or the MMRV vaccine into the routine UK schedule. As long as most children received the vaccine it would be very effective in reducing cases of severe chickenpox disease, but it is thought that cases of shingles in older people would increase. Shingles is very expensive for the NHS to treat. It is believed that many adults in the UK get their immunity to chickenpox boosted by coming into contact with children who have the disease. Several studies have shown that this may make adults less likely to develop shingles as they get older. If a chickenpox vaccine was introduced but not taken up by many people, there might be more adults who did not receive the vaccine or have “wild” chickenpox in childhood. They would then be at an increased risk of severe chickenpox infection as adults.

However, the JCVI is currently reviewing data from other countries where the vaccine has been in routine use over the past decade or two. It will use this to see what impact the chickenpox or MMRV vaccine is having on chickenpox and on shingles, and then advise the Government on whether there should be any change to the current advice on chickenpox vaccine. For more information see the JCVI minutes from October 2009.

Is the vaccine safe?

Because the chickenpox vaccine is live, there is a very small risk that someone who has been vaccinated could pass on the virus to someone who is not immune to chickenpox. This is usually only a risk if the person who has been vaccinated develops a chickenpox type rash at the injection site or elsewhere on the body.

The chickenpox vaccine should not be given to people who are clinically immunosuppressed (either due to drug treatment or underlying illness). This is because the vaccine strain could replicate too much and cause a serious infection. This includes babies whose mothers have had immunosuppressive treatment while they were pregnant or breastfeeding. For more information see the MHRA's Drug Safety Update (April 2016).

The chickenpox vaccine is not recommended for pregnant women as a matter of caution. Women who have had the vaccine are advised to avoid getting pregnant for one month after vaccination. However, studies have been carried out on pregnant women who have accidentally received chickenpox vaccine before they knew they were pregnant. These have not shown any link between the weakened virus in the vaccine and any specific problems in babies born to these women. See this Public Health England statement for more information.

Studies have shown that the vaccine virus does not get passed to the baby through breast milk, so it is safe for breast-feeding women to be vaccinated (see the Green Book chapter on Varicella, page 438).