Backgrounder: Vaccine Myths

The most effective way to protect yourself and your loved ones from flu viruses, including the H1N1 flu virus, is to get immunized.

It is important to know what is myth and what is fact. The following are among the more common myths surrounding flu vaccines, including both the seasonal and the H1N1 flu vaccines.

Myth 1: Vaccines don't work.

Fact 1: It is true that when there is an outbreak of a disease, some people who have been immunized get sick. This leads to the idea that vaccines don't work. Because each individual is different, about 10 to 15 per cent of people vaccinated will not develop immunity to the disease. Nevertheless, immunization reduces the risk of severe disease. In the case of the H1N1 flu virus, since very few people are immune, it is predicted that without interventions like a vaccine and antivirals, close to 25 to 35 per cent of the population could become ill over the period of a few months.  Immunization is the most effective way to prevent illness and to reduce the risk of transmitting the flu to those around you.

Myth 2: There are many serious side effects from vaccines.

Fact 2: We acknowledge that there are concerns with respect to immunization. There are some risks association with flu vaccine, but the potential risk for serious adverse events, like Guillan-Barré Syndrome, is low.

For regular seasonal influenza, about 5 to 10 percent of the population will get sick and on average about 4000 people die every year. The risks of serious side effects from the flu are far greater than the risk of experiencing an adverse event after receiving the flu shot. The risk of suffering Guillan-Barré as a complication from the flu is greater than the risk of getting it as a reaction to the flu shot.

Vaccines are among the safest tools of modern medicine. In Canada, serious side effects occur in about one out of every 100,000 doses of vaccine distributed. The vast majority of side effects from vaccines are minor and temporary, like a sore arm or mild fever. These are much less severe than influenza infection, and last for a much shorter time. No long-term effects have been associated with any vaccine currently in use.

Myth 3: Because the H1N1 flu vaccine is new, it is untested and unsafe.

Fact 3: Careful research into the safety of any vaccine is done prior to its widespread use. The requirements for vaccines approved for sale in Canada are stringent. Every vaccine lot is safety-tested by the manufacturer and by the Biologics and Genetic Therapies Directorate at Health Canada. Health Canada will review all available test results, including international data, to ensure the vaccine is safe and effective before it is authorized for use in Canada. The dangers of vaccine-preventable diseases are much greater than the risk from a serious reaction to a vaccine.

The use of an adjuvanted vaccine is not new. The adjuvant used in the H1N1 flu vaccine although new in Canada, has been widely used safely in Europe in other vaccines. This adjuvant has already been evaluated by Health Canada, and no safety concerns have been found.

Myth 4: Taking the regular flu shot puts me at risk of becoming very ill with H1N1

Fact 4:  Preliminary findings from some Canadian studies indicate that those healthy adults that tested positive for H1N1 were twice as likely to have received seasonal vaccine. More research is needed to establish whether or not there is a causal relationship between these factors. What is important is that there is no association with receiving seasonal vaccine and experiencing serious illness from H1N1.

Studies in Canada and the U.S. have shown that there appears to be no increased risk of severe disease from the H1N1 flu virus among people who received seasonal flu shots. Studies in the U.S., Australia and Britain have not shown an association between the seasonal flu shot and getting the H1N1 flu virus. 

Myth 5: The influenza vaccine can give you influenza.

Fact 5: The influenza vaccine cannot give you influenza. The influenza vaccine contains dead influenza viruses and they cannot cause infection.

Myth 6: Getting an influenza vaccine every year overwhelms and weakens the immune system.

Fact 6: The influenza vaccine gives you a high level of immunity to the virus. People who get the influenza vaccine every year are better protected against influenza than those who do not get it.

Myth 7: The influenza vaccine contains thimerosal (mercury), which is harmful, especially for young children.

Fact 7: The amount of thimerosal used in the influenza vaccine is very small and has not been shown to cause any harm. Canada's National Advisory Committee on Immunization (which includes recognized experts in the fields of paediatrics, infectious diseases, immunology, medical microbiology, internal medicine and public health) has reviewed the latest science and concluded, "there is no legitimate safety reason to avoid the use of thimerosal-containing products for children or older individuals."  The vaccines that Canadian children and adults receive are safe.

Myth 8: Pregnant women should not get the influenza vaccine.

Fact 8: The influenza vaccine is safe during pregnancy. Being immunized is the best way to protect yourself and those around you, including your unborn infant. It is also safe for babies to breastfeed after mothers receive the influenza vaccine.

Although women who are pregnant are not more likely to get the H1N1 flu virus, they are more likely to suffer complications if they do get infected. This is particularly true in the second and third trimester of the pregnancy.

If you have any questions about getting an influenza shot during your pregnancy, speak with your doctor or health care provider.

Myth 9: My child got the influenza vaccine (flu shot) last year so there is no need to give him the shot again. He is still protected against the virus.

Fact 9: It is important for children over the age of six months to be immunized every year to make sure their body forms antibodies against the most common strains of influenza viruses circulating that year. Because the flu viruses may change from year to year, the vaccine is updated annually, so your child should get the flu shot every year.

These are only a few of many myths circulating about immunization and the influenza vaccine (regular seasonal flu and H1N1).  When seeking information on such vital issue as your health, it is important to refer to official sources such as Health Canada, the Public Health Agency of Canada, and your provincial and territorial departments of health.

You can access current, updated information through www.fightflu.ca  or by calling toll-free 1 800 O-Canada (1-800-622-6232). Being and staying protected against any illness starts with knowing the facts.

Knowledge is Your Best Defence