October 23, 2013
News Review From Harvard Medical School -- Studies: Flu Shots Help Protect the Heart
Getting a flu shot may decrease your risk of a heart attack, a new study finds. And the benefit is greatest for people with known heart disease. The new research combined the data from 6 studies on flu vaccines. They included nearly 7,000 people. Their average age was 67. About 36% had a history of heart disease. People were randomly assigned to receive flu vaccine or a placebo (fake) shot. Researchers kept track of them for an average of 8 months. In that time, the new study found, those who got the real vaccine were 36% less likely to have a heart attack, heart failure or related problems than those who got the placebo. The new study also took a separate look at just the 3 studies that included people with known heart disease. In these studies, flu shots reduced people's risk of heart events by 55%. Flu shots are strongly recommended for people with heart disease. But this study is the largest one yet to show that they can help prevent heart attacks or other heart problems. The Journal of the American Medical Association published the study. HealthDay News wrote about it October 22.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
A nasty case of the flu can sideline normally healthy people for several days. But the influenza virus can be especially dangerous for people with heart disease. Every year, hospital stays and deaths related to heart disease spike during flu season.
Flu can harm the heart in several ways. The virus creates inflammation throughout the body, including the blood vessels. Inflammation in someone with coronary artery disease leads to more fatty deposits inside the arteries around the heart. These blood vessels supply oxygen and nutrients to the heart.
Even worse, inflammation increases the chance that one or more fatty deposits (plaques) will break open. When that happens, the fatty deposits release chemicals that trigger a blood clot to form and completely block blood flow. This is the major cause of heart attacks.
That's not all. In the lungs, the flu virus may damage the air sacs. Blood oxygen levels can fall, increasing strain on the heart. The virus itself also can injure heart muscle cells. This can cause heart failure or make existing heart failure worse.
It seems natural to assume that getting a flu shot would decrease the risk of flu-related heart problems. And some studies have suggested that it does. Now we have a very well done study that shows this in a more conclusive way.
Researchers found that getting the flu vaccine does indeed lower your risk of heart attack and other heart-related problems. People with a recent heart attack or angina that required a hospital stay received the most heart attack prevention from the vaccine.
What Changes Can I Make Now?
Everyone age 6 months and older should get a flu vaccine. This is especially true if you or someone you know is more likely to have severe health problems caused by flu. These groups include:
- Children younger than 5
- Pregnant women and women who are trying to get pregnant
- Adults 65 and older
- People under age 20 who take aspirin regularly
- People with heart disease, especially if they have had a heart attack or a hospital stay for angina in the last year.
- People with asthma, emphysema, chronic bronchitis or other lung disease
- People with any condition that can weaken the immune system, including diabetes
- People with a body mass index of 40 or higher
You also should get vaccinated if you are in regular contact with anyone at high risk of severe illness caused by flu. This is especially true if you have or care for a child too young to be vaccinated.
This season there is plenty of flu vaccine available. And, for the first time, you can get a vaccine not made from eggs. That means people with egg allergies can get vaccinated.
What Can I Expect Looking to the Future?
There are more vaccine varieties than ever. Depending on your age and health, your doctor or pharmacist can help you decide on the best one for you. But we don't know yet whether any particular vaccine provides more protection against the flu than others. Those studies are now underway.
Don't get hung up on the choice of vaccine. Just make it a priority to get vaccinated as soon as possible.