Pros and Cons of the Chickenpox Vaccine

Information on Chickenpox Vaccine (Varivax)

(adapted from HSE web site)


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) however as it is a “live” vaccine containing a weakened form of the virus, side effects are more common than with some other vaccines (see below).

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.


If the chickenpox vaccination is required, two doses are given with four to eight weeks between the doses. The doses are injected underneath the skin.

Who should have it

Healthcare workers

The chickenpox vaccination is recommended for healthcare workers who have no previous history of chickenpox. If you are uncertain whether you have had chickenpox in the past, contact your GP or occupational health department. A blood test will be used to check if you are immune to the disease.

Healthcare workers include anyone who is likely to come into contact with a patient, including medical and nursing staff and other workers such as:

  • hospital cleaners
  • hospital catering staff
  • ambulance staff
  • hospital or GP receptionists

Close contact with vulnerable people 

The chickenpox vaccination is also recommended for anyone who has no previous history of chickenpox and is likely to come into close contact with a person who has a weakened immune system.

If you think that you or a member of your family or household needs a vaccination, contact your GP for advice.

Children with severe disabilities living in residential units

The chickenpox vaccination is recommended for children with severe disabilities who never had chickenpox if they are living in special residential units.

Women of childbearing age

If you are a woman of childbearing age and think you never had chickenpox you should contact your GP for advice regarding vaccination. Vaccination is recommended for non-immune women of this age.

Who should not have it

People who have a weakened immune system should consult a doctor about whether or not they should have the vaccine.

The chickenpox vaccine should not be given to people who have experienced an anaphylactic reaction (serious allergic reaction) to a previous dose of the vaccine or to any of the ingredients used in the vaccine. If you are unsure whether this applies to you, ask your GP.

The chickenpox vaccine should not be given to pregnant women. If you are receiving the vaccine, do not become pregnant for three months after the last dose.

Vaccination is not recommended for people who are seriously unwell. It should be delayed until they recover.

Side Effects of the vaccine

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.

Other recognised side effects of the vaccine include Fever, upper respiratory infection, irritability and rash

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.


October 2015