Each year during flu season, at least one in every 20 people in the U.S. will come down with influenza or flu. Some years, that number can be as high as one in every five. For most of us, getting the flu means several days of feeling pretty miserable. Headaches, body aches, high fevers, chills, fatigue, and exhaustion are all part of the disease running its course. But then most people recover on their own.
But there are some people -- primarily young children, older adults, and people with chronic health conditions such as asthma -- who are at higher risk of seasonal flu-related complications. In the past decade, flu-related illnesses have resulted in the hospitalization of between 140,000 and 710,000 people and the deaths of 12,000 to 56,000 people.
The flu is caused by influenza viruses that are highly contagious. Fortunately, there are ways to protect yourself against seasonal flu, and the primary way to prevent it is to get an annual vaccination.
This article explains what you need to know about the seasonal flu vaccine.
Can Getting the Seasonal Flu Vaccine Cause the Flu?
There are actually two kinds of vaccines: One is given as a shot (an injection) and one is given as a nasal spray. The shot contains dead influenza viruses -- up to four different strains. The nasal spray is made with live viruses that have been weakened. Neither vaccine causes flu illness (although the nasal spray can result in congestion and runny nose). The strains of influenza virus within the vaccines are chosen each year based on what scientists predict will be the circulating viruses for the flu season. Both types of vaccine cause the body's immune system to create antibodies that will ward off influenza virus if it invades your body.
The nasal spray can be given to healthy, non-pregnant individuals ages 2 to 49. It should not be given to anyone with a chronic condition or weak immune system. That would include an illness that affects the immune system and people being treated with drugs or therapies that suppress the immune system. If you have any question about whether you or your child can use the nasal spray vaccine, talk with your doctor.
The flu shot can be given to anyone ages 6 months and older. Also available are intradermal shots. These injections, approved for those ages 18 to 64, use smaller needles and only go into the top layer of the skin instead of deeper into the muscle.
For those age 65 and older, a high-dose version of the flu vaccine called Fluzone is recommended when available. It may be more effective at protecting the elderly because their immune systems are more fragile.
Why Do People Need a Flu Vaccination Every Year?
The seasonal flu vaccine is changed every year. Each year, a panel of experts from agencies such as the FDA and the CDC studies the available data and decide which three or four strains of influenza viruses will most likely be active during the next flu season. In February, they advise the manufacturers which strains of viruses to use in making the vaccine. So, each year the vaccine being used is different than the vaccine used the year before.
How Effective Is the Seasonal Flu Vaccine?
The seasonal flu vaccine is about 80% effective in preventing flu. It takes about two weeks for the body to become protected after getting the seasonal flu vaccine.
The viruses used in the vaccine may not be the only strains causing the flu; it's possible you could be infected with a virus you do not have immunity against. People who get the flu after getting a flu shot typically have a milder and shorter case of flu.
Who Should Get a Seasonal Flu Vaccine?
The seasonal flu vaccine is recommended for all persons older than 6 months of age.
It's also recommended for adults considered to be at higher risk of complications. That includes:
- People with chronic diseases such as diabetes mellitus, kidney disease, heart disease, lung disease, and a weakened immune system, such as from HIV/AIDS or as a result of therapy.
- Pregnant women
- Residents of nursing homes and other facilities where people have chronic medical conditions
- Health care workers
- People planning to travel to the tropics at any time and people who were not vaccinated but are going to the Southern Hemisphere from April through September
- People ages 50 years and older. There are now high-dose vaccines made specifically for older people and their immune systems.
- Caregivers and household contacts of anyone in a high-risk group
The vaccine is also recommended for anyone else who wants to be protected against this year's flu.
If a child is between 6 months and 8 years and is being vaccinated against flu for the first time (or was vaccinated for the first time during the previous flu season but only got one dose), they should get two doses, separated by at least 4 weeks.
Are There Some People Who Should Not Get a Flu Vaccine?
People who should not get a flu shot include:
- Infants under age 6 months
- Anyone who has had a severe reaction to a past flu shot or nasal spray
- Someone with Guillain-Barre syndrome or chronic inflammatory demyelinating polyneuropathy
- People with moderate to severe illness with a fever; they should be vaccinated after they have recovered.
It's long been advised that people with allergies to eggs should not get the flu shot. However, the American College of Allergy, Asthma & Immunology says the vaccine contains such a low amount of egg protein that it's unlikely to cause an allergic reaction in those with an egg allergy. If you have a severe egg allergy (anaphylaxis), talk to your doctor before getting the flu vaccine. The vaccine should be given by a health care provider with experience in managing allergic signs and symptoms and should be watched closely for at least 30 minutes. Also, flu vaccines that do not contain eggs are available.
When Is the Right Time to Get Vaccinated for the Seasonal Flu?
The vaccine is usually available in early fall. It can take up to a couple of weeks for the body to build immunity to the flu. So, the best time to get a shot is as soon as the vaccine becomes available. But if you didn't get one before the season started, it's a good idea to still get one during the season to lower your risk of getting sick.
Are There Side Effects to the Flu Vaccine?
Some people experience soreness or swelling at the site of the flu shot injection. And some have mild side effects like a headache, cough, body aches, or fever. These usually clear up in about one to two days.
The nasal spray sometimes causes mild symptoms, including:
Where Can People Get a Flu Vaccine?
There are several places where you can go to get a flu vaccine, including:
- Health care settings such as a doctor's office and health clinics
- Community groups
The CDC's Flu.gov and the American Lung Association's web sites have an interactive seasonal flu clinic locator that you can use to find a location for a flu vaccine near you.