For Canadians, each new winter comes with a few certainties: hockey will dominate Saturday night television, holiday music will take over the malls, and Facebook feeds will spark with pro and con flu-shot debates. On social media, the conversation easily adopts the kind of fervour we normally expect from a Leafs vs. Habs game, making it hard to separate flu vaccine myths from flu vaccine facts. So we talked to Mt. Sinai Hospital microbiologist and infectious disease expert Dr. Allison McGeer, plus the flu team at Health Canada to give you the information you need to call the shots.
Here are their responses to 9 common beliefs about flu vaccines:
Can flu shots can cause the flu?
“Flu shots given by injection are made by killing the virus and then purifying the antigens (the proteins that stimulate the immune response),” says Dr. McGeer.
Each lot of vaccines is double-tested – by the company and by the Canadian government – to ensure safety. You won’t get sick from the flu shot, says Dr. McGeer, but a nasal spray vaccine might cause minor complaint. “The nasal spray vaccine is made of virus that has been ‘attenuated’ – or weakened – it does cause an infection, but is so weak that a slightly snuffly nose is usually the only result.”
It’s better for the immune system to catch the flu than to get the flu shot
“Vaccination of all types is the second most important reason (after safe water supplies) that we live longer and healthier lives than people did a century ago,” says Dr. McGeer. “Your immune system and mine are bombarded by thousands of antigens every day; there is no particular advantage to letting yourself get sick.”
Flu shots offer limited protection
For doctor McGeer, it’s a matter of perspective. “Influenza vaccine prevents about 60% of influenza in healthy adults, and makes those infections that do occur less severe. It would be great if we had a better vaccine (and people are working on it), but in the mean time, the vaccine we have is much better than nothing.” She notes that seatbelts and airbags don’t prevent all car accident deaths, but having them is still worthwhile.
The flu shot protects against all flus
“Flu,” says Dr. McGeer, “is a term that many people use to mean an acute illness of the upper respiratory tract (stuffy runny nose, sore throat, cough, etc.) that can be due to many different viruses. Influenza causes illness that is very similar, but is MUCH more likely to be complicated by ear infections, pneumonia, heart attacks, strokes and other serious complications.”
According to Health Canada, this year’s batch of flu vaccines protect against specific H1N1 and H3N2 influenza A viruses, and one influenza B strain. Some jurisdictions may also offer a quadrivalent vaccine that protects against four strains of flu viruses expected to cause illnesses. Check with your province or territory for the specifics in your region.
The flu is annoying, but not very serious.
Health Canada reminds us that flus result in an estimated 12,200 hospitalizations and 3,500 deaths in Canada each year. “Canadians are more likely to die from influenza than any other infectious disease,” adds Dr. McGeer. “For the population, influenza is a very serious illness.”
The flu shot is safe for pregnant women and nursing mothers
Not only is it safe, says Dr. McGeer, but the flu shot “protects women from hospitalization for respiratory illness in the late stages of pregnancy, and makes it less likely that their babies are born prematurely. Influenza vaccine is important for the health of every unborn baby.” Health Canada adds that everyone over the age of six months is encouraged to get a flu shot each year, as it offers the best protection against flu viruses.
People who have already had the flu this season don’t need the shot
“There are usually 2 or 3 influenza strains that cause infection every year – if you have had influenza from one of them, you still want to be protected against the others,” says Dr. McGeer.
Flu shots contain harmful preservatives
“Nasal spray vaccines and injectable vaccines that are prepared as single doses contain no preservative,” says Dr. McGeer. “Injectable vaccines in multi-dose vials have thimerosal as a preservative to prevent contamination. Thimerosal is an organic mercury compound which occurs naturally and is found in many foods. The amount you get in an influenza vaccine is about the same amount that you would absorb from a liter of milk. There is good evidence that this amount is not harmful.”
There’s no point in getting the shot at the very end of the season
In Canada, flu season usually runs from November to April, says Health Canada, adding that it takes up to two weeks for the body to build immunity after getting the shot. “If you aren’t going to travel to other parts of the world (where influenza can occur at different times of the year),” says Dr. McGeer, “the amount of benefit from the influenza vaccine decreases steadily over the season. By late February or March, it isn’t worth it to get vaccinated. But in January, it is not too late.”
To learn more about the flu and flu vaccines see FightFlu.ca. To find out where you can get a flu shot, visit your provincial health authority website. Or, if you’re a resident of BC, Alberta, Ontario, New Brunswick or Nova Scotia simply take a trip to your local drugstore, as pharmacists in those provinces are authorized to give the vaccine.