Understanding risk

Benefits of vaccines

A Change of Heart


As with any medical procedure, vaccines have some risks but these risks are extremely small. Most vaccine side effects are mild and temporary. Serious side effects are extremely rare. For example, the risk of a serious allergic reaction to a vaccine is about a one in a million. The risks from the diseases vaccines prevent, on the other hand, are much greater. These diseases can lead to complications such as pneumonia, deafness, brain damage, heart problems, blindness, paralysis and carry a risk of life-long disability and death.

We need to focus on the bigger risks, with the more dangerous consequences. Worrying about the tiny risks of a vaccine instead of the much larger risk from the disease is kind of like someone constantly watching the sky because they're worried about being hit by an aircraft and wandering into the path of a car instead.

Did you know?

According to the National Weather Service, the risk of being struck by lightning in a given year is about 1 in 1,000,000.  This is about the same risk of experiencing anaphylaxis after administration of a vaccine. 

Putting risk into perspective

Every action we take has risks. We tend to think of actions as riskier when we are less familiar with them while we tend to overlook the dangers of everyday life. For example, many people are afraid of flying and choose to drive instead, while the risk of dying in a car crash is much higher than the risk of dying in a plane crash.

Disease risk versus vaccine risk

If a child gets sick with a vaccine-preventable disease, the risk of complications is far greater than the risk of any side effect from a vaccine. This table from the Canadian Pediatric Society compares the risks from the diseases to the risks from vaccines: 


Bottom line: The risks from the diseases vaccines prevent are much greater than the risks of the vaccines. Immunization is by far your safest bet.