Varicella, or chickenpox, is a common, preventable disease that is caused by the Varicella zoster virus. It causes a fever and an itchy, blister-like rash. In fact, a person with chickenpox may have as many as 500 blisters all over their body. Chickenpox can be serious and even life-threatening to babies, adolescents, pregnant women, adults and people with weakened immune systems.

How varicella is spread

Chickenpox spreads easily through the air when an infected person coughs or sneezes. People can catch it by:

  • breathing the air where an infected person has coughed or sneezed
  • touching an infected surface, and then touching their nose or mouth
  • touching a chickenpox blister, or the liquid from a blister

A pregnant individual who has chickenpox can pass it on to their unborn baby.

A person with chickenpox can spread the disease for 1 to 2 days before they get the rash until all the blisters have turned into scabs. Scabs form in about 5 days.

Risks of varicella

Chickenpox can cause serious problems, such as:

  • sepsis (an infection in the blood)
  • pneumonia (an infection in the lungs)
  • encephalitis (an infection in the brain)
  • babies who get chickenpox from their mother before birth may be born with defects such as skin scars, brain damage, or arms and legs that are not fully formed
  • pregnant individuals who get chickenpox can miscarry

If chickenpox blisters get infected, this can lead to a serious illness called necrotizing fasciitis (also known as “flesh-eating disease”).

Chickenpox can be a mild disease in children, but there’s no way to know who will have a mild case and who will become very sick.

If one of your children has chickenpox, it will likely spread to family members or friends who have not had chickenpox or the chickenpox vaccine. Symptoms appear 10 to 21 days after people are infected and last for about 2 weeks.

People who have had chickenpox can be at risk for a disease called herpes zoster (also known as shingles). This is because the virus that causes chickenpox stays in the body and can flare up many years later and cause shingles, a very painful skin condition that causes a rash.


The most common symptoms of chickenpox are:

  • a rash that turns into very itchy, fluid-filled blisters and then scabs; the rash starts on the face, chest or back, and spreads to the rest of the body
  • fever
  • feeling very tired

Protection and prevention

You can protect your children against chickenpox with a safe and effective varicella vaccine. For the best protection against chickenpox, children need to receive the 2 recommended doses of the vaccine. The vaccine is given:

  • at 15 months of age
  • between 4 and 6 years of age

If there is a chickenpox outbreak in your community and you have not had the vaccine, you are at risk! When your child gets the chickenpox vaccine, they are getting immunity from chickenpox without the risk of serious problems from the disease.

The vaccines are part of the publicly funded vaccine schedule and are offered free to all children in Ontario. To attend school in Ontario, the chickenpox vaccine is required for children born in 2010 or after and for children attending a daycare unless they have a valid exemption.

The vaccine is also free for people who have certain medical conditions.

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