Fact or Fiction? Your guide to common immunization misconceptions

Fact or Fiction? Your guide to common immunization misconceptions


In early January, in the wake of a measles outbreak in California, I fielded many calls regarding immunization. I was happy to comfort those who had already been vaccinated, and counselled those who had not, to come in as soon as possible. The efficacy of a single dose of measles vaccine is estimated to be 85% to 95%, and with a second dose rises to almost 100%. This is excellent news for parents and children since measles is otherwise very contagious and spreads easily in the absence of immunization.

Measles is just one example of the diseases that are making a comeback due to decreased immunization rates in our communities. Polio is also on the rise in countries where for many years there had been no reported cases. Whooping cough (pertussis) has made increased appearances in Canada and the United States, and when NHL players were recently seen with swollen parotid glands, mumps has suddenly come back into the spotlight.

According to the Public Health Agency of Canada, in the past 50 years, immunization has saved more lives in Canada than any other health intervention. So with such impressive results, why are our immunization rates dropping? It is often because of many common misconceptions.

Myth #1: Getting too many vaccines could overwhelm my child’s immune system.


Fact: By far, the most common misconception – scientific evidence shows that giving several vaccines at the same time has no adverse effect on a child’s immune system. Children are exposed to several hundred foreign substances (antigens) that trigger an immune response every day. Their bodies constantly face things that challenge their immune systems, such as bacteria that lines our skin, nose, throat and intestines, as well as bacteria in food, water and air.

Immunologists and microbiologists looked into the number of immunological challenges a person can respond to at one time. After considering the variety of compounds in vaccines, they calculated that young children could safely respond to as many as 10,000 vaccines at once. We currently recommend that children get vaccinated against 13 diseases over a two-year period. Also, vaccines have become more refined over time – there are fewer antigens in the vaccines now than there were 20 years ago.

Myth #2: Vaccines can contain ingredients that are dangerous.


Fact: The one substance parents often hear about is thimerosal. Thimerosal is an organic compound containing a form of mercury (called ethylmercury) that is used as a preservative to prevent contamination.

There is no evidence ethylmercury is harmful, and there has been considerable research to prove that.

The World Health Organization, the Centres for Disease Control, and Health Canada looked at thimerosal and all found the same conclusion: no connection to any diseases. However, because some parents were alarmed, thimerosal has since been removed from any of the routine childhood vaccines.

Thimerosal is broken down by the body to ethylmercury, which is different than methylmercury, which is the chemical actually known to cause harm. To try to equate ethylmercury to methylmercury is like saying that ethyl alcohol, which is present in a glass of wine, is the same thing as methyl alcohol, which is the antifreeze that’s put in a car. They are not the same thing.

Myth #3: The measles, mumps and rubella (MMR) vaccine causes autism.


Fact: This myth started in 1998, when a study authored by Dr. Andrew Wakefield and colleagues was published in the medical journal, The Lancet. Recently, the editors of The Lancet officially retracted the paper, citing evidence that it contained false information. Dr. Wakefield has since been stripped of his medical license. Unfortunately, the study set off panic, causing vaccination results to drop and rates of measles to skyrocket.

Many other studies, including ones published in the Journal of the American Medical Association and the British Medical Journal, have shown that autism is not linked to the MMR vaccine. One of the largest long-term studies was published in the New England Journal of Medicine in 2002. Following 537,000 children, the study found the rates of autism were the same among kids who had been vaccinated and those that had not. After extensive reviews, the Canadian Pediatric Society, the American Academy of Pediatrics, the World Health Organization and other major medical authorities have all concluded the same thing: the MMR vaccine is not causing the rise in autism.

Myth #4: Vaccine-preventable diseases are almost eradicated in Canada, so there is no reason to be vaccinated.


Fact: Although vaccine preventable diseases have become uncommon in many countries, the infectious agents that cause them continue to circulate in some parts of the world. In a highly inter-connected world, these agents can cross geographical borders and infect anyone who is not protected. For example, with recent resurgence of polio in Israel, we’ve had to ensure students going on school trips receive a polio booster and do not contract this disease while away, and more importantly do not “import” it back to Canada.  Successful vaccination programs, like successful societies, depend on the cooperation of every individual to ensure the good of all. We should not rely on people around us to stop the spread of disease; we, too, must do what we can.