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Column originally published Feb 24, 1999
Column last revised/updated on Oct 23, 2018

All Children Should Get Chickenpox Vaccine

Question: I am an elementary school teacher. I was told by my mother that I have never had chickenpox. I have a one-year-old daughter and she didn’t have chickenpox yet. I was told that if I get chickenpox now as an adult, I can get really sick. Recently I heard the chickenpox vaccine has been licensed in Canada. Do you think my daughter or I should take this vaccine?


You are right, chickenpox vaccine has just been licensed in Canada. In order to help you to make that decision, and to help other readers who may have similar questions, let me give some background information on chickenpox and this new vaccine.

Chickenpox is a very common infection in young children. Most women already had the infection when they were growing up. As a result, they would pass on antibodies through the placenta to their children before birth. These antibodies are protective for several months only. Therefore, most children do not get chickenpox until they are close to one year of age and after.

In general, chickenpox is a mild illness that lasts about one week. Some children have very few pox lesions, while others can be plastered with numerous spots all over the body. It is rather itchy and uncomfortable, but the majority of children recover without complications.

However, in the last decade, there are increasing number of children who develop secondary bacterial infection in these pox lesions. A very small number had actually died because of a dangerous strain of Group A Streptococcus.

By the time children turn teenagers, the chance is that they would have been infected with chickenpox. However, there are always a few who would escape infection. If these uninfected teenagers and adults get chickenpox, the infection is usually much more serious. Many of them will develop complications like pneumonia.

In the early 1970s, a group of Japanese scientists started developing a live chickenpox vaccine. They began by removing the fluid from a pox in a healthy child with chickenpox, and grew the virus in cell cultures. After passing the virus through 31 successive cultures, they produced a weakened virus, which is now known as the Oka/Merck chickenpox vaccine.

This vaccine has been licensed in Japan, Korea, some European countries, and in 1995 in United States. There was extensive testing in many children and some adults before license was granted in United States and Canada. These tests have shown that the vaccine is both effective and safe.

The vaccine is recommended for children 12 months of age and older. The dose is 0.5 ml given by injection. It can be given together with other vaccines, but has to be given at a different site. The main side effects are local swelling and redness, with occasional low grade fever. A very small percentage of these children will actually develop several pox lesions around the injection site or in other parts of the body. But these are usually very few and very small, and do not make the child sick.

The great majority of children respond well to the vaccine and are protected from future chickenpox infection. If you ever wonder how long this protection will last, the answer is that we still don’t know. When vaccinated children were followed for up to 10 years, they have retained their protection against chickenpox. More interestingly is that many have stronger immunity than shortly after vaccination. This is likely because they were exposed to friends who had chickenpox infection, and got a boost in their immunity.

If you want your daughter to receive this new chickenpox vaccine, you will have to get it through your family doctor. At the present time, none of the provincial health departments have incorporated this vaccine into their immunization programs. The chance is that this will not happen soon. One reason is that chickenpox is such a common illness, and most children don’t get too sick with it.

Vaccinating adults is a different problem. Research has shown that most adults who cannot remember whether they had chickenpox were actually infected. Either they had a very mild illness, or in rare cases, they might not have pox lesions but developed immunity anyway.

As a result, before vaccination is considered, adults should have a blood test to determine whether they have chickenpox immunity. Since you are a school teacher, the chance is that you have already been infected without ever knowing it.

If you are confirmed to have no immunity to chickenpox, you certainly should be vaccinated. You will need two injections separated by 4 to 8 weeks.

One precaution is that you should make sure that you are not pregnant, and will not become pregnant for one month following the second injection. This is only a precaution, since we don’t know the effect of vaccine on the fetus. There have been rare reports of the natural chickenpox virus affecting the fetus in pregnant women.

The chickenpox vaccine does not contain any preservative or egg protein. However, it does contain traces of gelatin and an antibiotic neomycin. For those who have anaphylactic reaction to these two substances (that means getting into shock when exposed to them), they should not get the vaccine.

You may have heard that children with chickenpox should not receive aspirin. A very serious and sometimes fatal condition called Reye syndrome can happen. Because of this concern, it is also advisable to avoid using aspirin within 6 weeks after receiving this chickenpox vaccine.

There are still more details about the vaccine that I cannot explain here. If you have specific questions, you should discuss it with your doctor, or call the Department of Health in your area.

[Note to Readers: Chickenpox vaccine has been fully implemented across Canada for a number of years already. This has produced the herd immunity so that it is uncommon for any child to develop natural chickenpox infection.]