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Ask Dr. Marla: Is it possible that a chickenpox vaccine didn’t take?


My child had the chickenpox vaccine when he was a baby but now has the chickenpox (he’s eight). Is it possible the vaccine didn’t take? Have you ever heard of that?


It sounds like the vaccine gave your child immunity, but it was not long lasting. As a result, seven years after the initial vaccine, your child had chickenpox, but I bet it was a mild case. The vaccine likely shortened the course and severity of the disease.

We have subsequently learned that chickenpox vaccine, just like the measles, mumps and rubella (MMR) vaccine, requires a second vaccine to boost the existing immunity from the first vaccine and offer long-lasting immunity. As a result, we now offer a second vaccine called MMRV – all four viruses together, between ages four and six, or as two separate vaccines MMR and VZ (varicella zoster). It is estimated that 90 percent of children who are not vaccinated will get chickenpox by the time they are 12.

The chickenpox vaccine was licensed for use in Canada in 1998. The National Advisory Committee on Immunization (NACI) recommends that healthy children 12 months to 12 years of age should receive TWO doses of varicella-containing vaccine (univalent varicella or MMRV) for primary immunization. 

What are the side effects of chickenpox?

Severe cases of chickenpox are not so benign. It can pose serious health risks, especially for newborn babies, adults, or anyone with a weakened immune system. According to Health Canada, complications from chickenpox can include:

  • bacterial skin infections
  • scars (if the blisters get infected)
  • pneumonia
  • encephalitis (inflammation of the brain).
  • increased risk of birth defects for babies who get chickenpox from their mothers before birth.

However, the side effects are mild, temporary and far less harmful than the potential complications from a serious case of chickenpox. Side effects include:

  • a sore spot where the needle went in;
  • a mild fever that lasts for a few days.
  • a rash that resembles a mild case of chickenpox within a week or two of vaccination. The rash will clear up in about five days.

Do I need to keep my child away from other kids when he has the chickenpox?

NACI recommends people who have or suspect that they have chickenpox should avoid public places for at least five days after the first crop of lesions appears. People to whom exposure to varicella can be life-threatening include newborns, people with depressed immunity and people with serious illnesses like cancer .

Do I need to keep my child away from adults while he has the chickenpox to prevent them from getting shingles?

Shingles is a very painful rash of blisters which can be very debilitating for some. It is caused by the same varicella virus, which lies dormant in people after they have had the chickenpox. As we age and our immune system gets weaker, we can reactivate the virus.

This reactivation is not caused by exposure to the virus, so you don’t need to worry about keeping your child with chickenpox away from adults who may have had chickenpox and who are therefore susceptible to shingles.

There is a shingles vaccine for people over age 50 to boost their existing immunity to the reactivation of the virus, lessening the risk of shingles.

Got a question? Submit it to Dr. Marla.

Originally published in ParentsCanada magazine, December 2013.

a man carrying two children

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