Varicella, also known as chickenpox, was a common childhood disease occurring worldwide before the varicella (chickenpox) vaccine became widely used. In countries without vaccination programs for chickenpox, 50% of children get the disease before age 5, and 90% get it before age 12. Ontario has had a vaccination program since 2004, resulting in a large decrease in cases.
Chickenpox is caused by the varicella-zoster virus. It spreads easily when a person with chickenpox coughs or sneezes. You can become infected if you breathe in air or touch surfaces that are infected with the virus, or have close contact with someone who is contagious. The virus can also spread through contact with the fluid from chickenpox blisters (fluid-filled bumps). People with chickenpox are contagious starting 1-2 days before the rash appears until the last blister has scabbed over. Cases often increase during the school year, and decrease over the summer.
Symptoms usually start between 14-16 days after exposure, but can happen anywhere between 10-21 days after exposure. Chickenpox usually starts with fever, cough, sore throat and general aches and pains. Itchy, red rashes appear and can spread to almost anywhere on the body. The rashes will gradually form into blisters and then scab over.
In healthy children, chickenpox can be relatively mild. However, complications can still happen including pneumonia (lung infection), blood and skin infections or swelling of the brain. An infection in pregnancy can cause congenital varicella syndrome and an infection in newborns can cause severe neonatal varicella. People with a weakened immune system can also get very ill.
After a chickenpox infection, many years later a painful rash can occur, called herpes zoster or shingles.
Vaccination against chickenpox is very safe and effective.
Children receive one dose of vaccine against varicella on its own, routinely at 15 months of age, then again as part of the measles, mumps, rubella, and varicella (MMRV) vaccine, which is routinely given at 4-6 years of age.
The varicella vaccine is very safe. The majority of reported side effects are mild, including fever, rash, and injection site reactions. The efficacy of varicella vaccines is estimated to be 94.4% following one dose, and 98.3% following two doses.
Learn more about MMR and MMRV Vaccines including the risks associated with vaccination against varicella, vaccination against varicella as part of the MMRV vaccine, people who should avoid or delay vaccination, and people who should be prioritized.
Health care providers generally diagnose chickenpox based on the characteristic rash, but if there is any doubt, a blood test, and a test using fluid from blisters, are available to confirm. This blood test can be used to find out if someone has chickenpox, recently had it, or is immune to the disease after an infection or vaccination.
In healthy children, chickenpox typically does not need to be treated, but medications may be prescribed to relieve itching or fever. The following are recommended to ease the symptoms of chickenpox at home:
People at risk of complications may be prescribed antiviral medications to shorten the length of the infection to reduce their risk. If complications do occur, for example skin infections or pneumonia, antibiotics may be prescribed.
Talk to a health care provider to find out what treatment options might be available.
Post-exposure immunization may be required depending on the level of exposure to chickenpox. Post-exposure management of healthy infants less than 12 months of age is not indicated as these infants are generally protected by maternal antibodies.
The following situations are considered significant exposures as a result of having contact with a person who has chickenpox:
After being exposed, the chickenpox vaccine (not the MMRV vaccine) is generally provided to susceptible individuals. For optimal effectiveness, it should be given within 72 hours after exposure and up to 5 days later. Varicella immune globulin may also be considered.
Please contact your health care provider for advice specific to your situation.