Influenza Can Have Deadly Consequences for Individuals with Heart Disease?

Written by : John A. Sawdon, Public Education & Special Projects Director Cardiac Health Foundation of Canada

With the arrival of Autumn we experience falling temperatures, the magic of brilliant colours of leaves before they make their way to the ground and the perils of the flu season. Flu symptoms can include the Following:

  • Fever or feeling feverish/chills
  • Cough
  • Sore throat
  • Runny or stuffy nose
  • Muscle or body aches
  • Headaches
  • Fatigue or tiredness
  • Some people may have vomiting and Diarreha, this is more common in children

The flu is difficult for everyone but can pose serious consequences for individuals with Heart Disease, Congestive Heart Failure, Congenital Heart Disease and those who have had a stroke. “Among adults hospitalized with the flu during the 2015/2016 influenza season, heart disease was among the most commonly occurring chronic condition, 41% of adults hospitalized with the flu during the 2015/16 season had heart disease”(1). Research shows that influenza outbreaks are associated with a rise in deaths from heart disease and the flu can trigger heart attacks and strokes. Dr Madjid from the Texas Heart Institute studied deaths between 1993 and 2000 in St. Petersburg of the Russian Federation and found that peaks in deaths from acute myocardial infarction and chronic ischemic heart disease peaks during influenza epidemics. (2) Researchers believe that the Influenza contributes to heart attacks and strokes in two ways; the flu causes acute and severe inflammation in the body which, in some cases, destabilizes atherosclerotic plaques in coronary arteries. The inflammation leads to the rupture of these vulnerable plaques and the formation of clots which causes heart attacks and strokes. In the second way the flu can cause bacterial pneumonia. Pneumonia is a lung infection that prevents your lungs from getting enough oxygen into the blood, which then puts a strain on your heart. It means your heart has to work that much harder to pump blood through your lungs.
Over a 31 year period between 1976 and 2007 estimates of flu related deaths in the United States range from an annual low of 3,000 individuals to a high of 49,000 people. (3) In Canada this ranged from a low of 1500 individuals to a high of 10,000 people (4) During recent flu seasons between 80 to 90% of flu related deaths have occurred in people 65 years of age and older.

Influenza Vaccine May Reduce Risk of Heart Disease and Death

Dr. Jacob Udell a cardiologist at Women’s College Hospital Toronto and University of Toronto & his team from TIMI Study Group & Network for Innovation in Clinical Research found that the flu vaccine provided approximately a 50% reduction in risk of a major cardiac event compared to placebo group after one year.(5) A similar trial also found a 40% reduction in death from any cause for those receiving a flu vaccine. Clinician’s have long noticed that 30% of heart attacks are preceded by upper respiratory infection that is consistent with influenza. Influenza vaccination was also associated with a 67% reduction in risk of heart attacks during influenza season. Two other related studies found a 49% reduction of out of hospital primary cardiac arrest and a 50% risk reduction in stroke risk for individuals receiving the influenza vaccination. (6)

Other Benefits of the Influenza Flu Vaccine:

  • It can keep you from getting sick and if you do get the flu, it will be milder
  • A 2014 published study showed flu vaccine reduced children’s risk of flu related paediatric intensive care unit admissions by 74% between 2010 & 2012
  • A 2016 study showed that people 50 years and older who got a flu vaccine reduced their risk of getting hospitalized from flu by 57%
  • Vaccination is also associated with lower rates of cardiac events among people with heart disease, especially those who had a cardiac event within the past year
  • The Flu vaccine has been shown to reduce hospitalization among people with Diabetes by 79% and chronic lung disease by 52%
  • Getting vaccinated protects people around you especially those who are vulnerable to getting sick as well as children (7)

How do Flu Vaccines Work and What do they protect against?

Flu vaccines usually take approximately 2 weeks to create anti-bodies. These anti-bodies then provide protection against infection with the viruses in the vaccine. Traditional Flu vaccines, called Trivalent Inactivated Influenza Vaccines are made to protect you against 3 viruses:

  • Influenza A( H1N1) Virus
  • Influenza A(H3N2) Virus
  • Influenza B Virus
  • The current trivalent inactivated influenza vaccines available for use in Canada are:
    • Agriflu (Novartis)
    • Fluviral (GlaxoSmithKline)
    • Fluzone (Sanofi Pasteur)
    • Influvac (BGP PHarma ULC) May be called Abbott
    • Vaxigrip (Sanofi Pasteur)

There is also a New High Dose Trivalent Inactivated Influenza Vaccines that was approved by Health Canada in 2016. This High Dose Trivalent Vaccine has been approved in the United States since 2009.

The High Dose Vaccine available in Canada is called:

  • Fluzone High Dose (Sanofi Pasteur)

There is also a Flu Vaccine that protects against a Fourth Virus. It is called Quadrivalent Vaccines. It protects against the above 3 viruses and also a second Influenza B Virus. The current quadrivalent inactivated Influenza vaccines available for use In Canada are (8):

  • Flulaval Tetra (GlaxoSmithKline)
  • Fluzone Quadrivalent (Sanofi Pasteur)

Potential Influenza Inactivated Flu Vaccines Side Effects

The flu vaccine cannot give you the flu. Flu vaccine viruses have been “inactivated” and are not infectious. In the location where you are given your injection, it is possible for the following to occur:

  • Soreness, redness or minor swelling around the injection site
  • A Low grade fever
  • Aches

Influenza Flu and Medication effect:

If you are on warfarin(which is a blood thinner) it is important to know that a cold or flu like symptoms can affect your blood clotting risk (INR). If you are sick and are on warfarin discuss monitoring your INR levels with your Doctor.

Six Steps to Staying Healthy (9)

  • Get the Influenza flu shot early
  • Wash your Hands often
  • Avoid touching your eyes and face
  • Cover your cough or sneeze into a Kleenex or cloth
  • Do not share drinking utensils
  • Do a fist pump instead of a hand shake

We encourage you to either go to your Doctor for a flu vaccine shot or to one of the many pharmacists which provide free flu shots. If you are in doubt as to whether the flu shot is for you, discuss these concerns with your Doctor or Pharmacist. Our goal is to provide information so that you are informed and can raise questions and concerns with health practitioners. We hope this article is helpful and would love to receive your feedback. Please send any comments to jsawdon@cardiachealth.ca


  1. CDC Centers For Disease Control and Prevention; Flu and Heart Disease & Stroke http://www.cdc.gov/flu/heartdisease/index.htm
  2. Texas Heart Institute; Research Shows Flu Can Trigger Heart Attacks http://www.texasheart.org/HIC/Topics/Cond/Flu_heartattack.cfm
  3. CDC Centers For Disease Control and Prevention; Key Facts About Seasonal Flu Vaccine; http://www.cdc.gov/flu/protect/keyfacts.htm.
  4. CARP Hosts Expert Panel: The True Cost of Influenza Thursday, September 22nd, 2016 at 9:30 a.m.
  5. News National; Flu shots may cut the risk of heart attacks, death from heart disease, Canadian research suggests. http://o.canada.com/news/national/1028-flu-shot
  6. Mohammed Madjid; Morteza Naghavi; Silvio Litovsky and S. Ward Casscells; Influenza and Cardiovascular Disease, American Heart Association, http://circ.ahajournals.org/content/108/22/2730
  7. CDC Centers For Disease Control and Prevention; Flu and Heart Disease & Stroke http://www.cdc.gov/flu/heartdisease/index.htm
  8. Public Health Agency of Canada; Protecting Canadians from Illness, An Advisory Committee Statement (ACS) National Advisory Committee on Immunization (NACI) Canadian Immunization Guide Chapter on Influenza and Statement on Seasonal Influenza Vaccine for 2016-2017
  9. Communicable Disease Control, City of Toronto September 2016; http://www1.toronto.ca/wps/portal/contentonly?vgnextoid=5ed64485d1210410VgnVCM10000071d60f89RCRD
  10. Kristin L. Nichol M.D. M.P.H., MBA; James Nordin M.D. M.P.H., John Mullooly Ph.D, Richard Lask M.D., Kelly Filbrandt B. S. and Marika Iwane Ph. D; Influenza Vaccination and Reduction in Hospitalizations for Cardiac Disease and Stroke among the Elderly; 2003 http://www.nejm.org/doi/full/10.1056/NEJMoa025028
  11. Mayo Clinic Flu Shots: Especially Important if you have Heart Disease, http://www.mayoclinic.org/diseases-conditions/heart-disease/in-depth/flu-shots/art-20044238

The articles, on the Cardiac Health Foundation of Canada website, are presented with the understanding that the Foundation is providing information only and not rendering medical advice. Please check with your family physician, specialist or health care professional before implementing any of the ideas expressed in these articles.