Chickenpox is a highly contagious viral illness, which in children is usually a fairly mild illness producing a temperature, cough and an itchy rash. Most children miss a week or so of school and quickly return to normal good health. Serious complications such as pneumonia and encephalitis are uncommon. Once infected children have lifelong immunity. There is now a vaccine to protect children from chickenpox.

When unvaccinated adults catch chickenpox it is more serious.

Chickenpox causes

Chickenpox is caused by a herpes virus — varicella-zoster. It spreads rapidly via airborne droplets from coughing or sneezing, direct contact with the rash, or contact with sheets or clothes recently used by an infected person. Chickenpox is easily caught. An infection normally gives life-long immunity to further attacks.


Chickenpox symptoms appear about 2 weeks after being exposed to the virus.

  • Flu-like symptoms, such as fever, headache and runny nose and generally feeling unwell, usually appear first.
  • Rash is also one of the first symptoms. It begins as very itchy clusters of spots, usually on the face.
  • The rash will spread to other parts of the body, such as your legs, arms and torso.
  • After a few days, the rash will become fluid-filled blisters. You can have different stages of the rash on your body at the same time.
  • The final stage of the rash is when the spots crust over and form scabs.


For those adults who didn’t catch chickenpox in childhood, or who haven’t been vaccinated, an attack of chickenpox can produce serious, sometimes lethal, complications.

Adults are at risk of pneumonia and, less commonly, meningitis or encephalitis (infection of the brain).

Particularly at risk are smokers, those with lung disease, pregnant women, and people who are immunocompromised or on chemotherapy. Infection in pregnancy can affect the baby and produce severe abnormalities. Infection of the lesions is another complication.

Another, often unexpected, complication occurs when the virus reactivates and causes shingles many years after the initial chickenpox episode.

Who can get chickenpox?

Anyone (adult or child) who has not been vaccinated, or has not had chickenpox before, is at risk of catching chickenpox. Rarely, someone who has been vaccinated will catch chickenpox, but the disease will be much less severe and less contagious than in an unvaccinated person.

Preventing chickenpox

Chickenpox vaccination is now free for children as part of the National Immunisation Programme Schedule. It is given as one dose at 18 months of age as MMRV (measles, mumps, rubella, varicella) vaccine. There are catch-up programs for children who missed this vaccination.

Adults who are unsure if they had chickenpox as a child should consider being tested to see if they are immune to the disease. This is particularly important if they are likely to be in contact with children, the main source of infections.

Adults who are not immune can be vaccinated against varicella-zoster so that they are protected if they do come into contact with chickenpox sufferers. They will need 2 doses, at least one month apart.

In certain cases, an injection of a medicine called Zoster Immunoglobulin may be given to non-immune people following contact with chickenpox sufferers. This medication contains antibodies to the varicella-zoster virus, and can prevent or modify an attack of chickenpox when given within 96 hours of exposure, reducing the risk of serious complications.

How long am I infectious for?

People with chickenpox should avoid contact with other people and not attend childcare or school until at least 5 days after the rash started, and all the blisters have dried.

Chickenpox and pregnancy

Pregnant women should avoid people with chickenpox and see their doctor if they think they have been exposed to someone with chickenpox.