The single best way to prevent the flu is to get a flu vaccination each year. You can get the vaccine at your doctor’s office and at some workplaces, supermarkets, and drugstores. There are two types of vaccines.
- Flu shot. Given via a needle, the flu shot injects into your body a vaccine that contains an inactive virus that has been killed with heat, chemicals, or radiation. Because the virus has been killed, it cannot infect you. Once more: a flu shot cannot give you the flu. The flu shot is approved for use in people six months of age and older, including people with chronic medical conditions.
- Nasal spray flu vaccine (FluMist). The nasal spray flu vaccine (sometimes called LAIV for live attenuated influenza vaccine) is made with live, weakened flu viruses that generally cannot cause the flu. There is an extremely small risk that the virus in LAIV could mutate and regain the ability to cause the disease (all living organisms can mutate). This risk is greatest in people with already weakened immune systems. That’s why LAIV is approved only for use in healthy people two to 49 years of age who are not pregnant. People who are 50 or older, women who are pregnant, or those who have a weakened immune system (or live with someone who does) should get the flu shot instead of the nasal spray, as should babies age six months to two years.
No matter which vaccine you get, about two weeks after vaccination, your immune system develops proteins called antibodies that protect against infection from flu viruses. Flu vaccines will not protect you from colds or other flu-like illnesses caused by non-influenza viruses.
You must get a flu vaccine every year to be protected. The vaccine is different from year to year because the strains of flu viruses that are expected to infect people change from year to year. The vaccine preparation is based on the strains of the flu viruses that scientists anticipate will circulate that winter. Sometimes an unpredicted strain may appear after the vaccine has been made. This is why you may still get the flu even if you’ve been vaccinated. But if this happens, the disease is usually milder because the vaccine will give you some protection. As mentioned previously, a flu shot cannot cause the flu, but if you were to be exposed to a different flu virus right before you got vaccinated, you could get the flu and think it was because of the vaccination.
October to November is the best time to get vaccinated, but getting vaccinated in December or even later can still be beneficial since peak influenza activity usually occurs in February or later. The flu season can last as late as May.
In general, everyone over the age of six months should consider vaccination. However, sometimes there are flu vaccine shortages, usually due to a higher-than-expected demand or problems producing the vaccine. In these cases, the national Advisory Committee on Immunization Practices makes recommendations about which groups should get the vaccine first, based on their risk of flu-related complications. If you hear of a vaccine shortage and are not in a high-risk group, wait to get a flu shot until more vaccine is available.
Who should get vaccinated?
In general, all children over the age of 6 months and all teenagers and adults should get vaccinated. Since children younger than six months cannot get vaccinated, it is important for people living with these children to do so.
Getting a flu vaccine is especially important for people at high risk for serious flu-related complications and those who live with or care for people at high risk, including:
- children and adolescents ages six months to 18 years of age, especially those who are on aspirin therapy
- pregnant women and women planning to become pregnant during the flu season
- people age 50 years and older
- people of any age with anemia, heart disease, diabetes, kidney disease, a compromised immune system, or a chronic lung disease
- people who live in a nursing home or other long-term-care facility
- medical personnel.
Even if you do not fall into one of these high-risk categories, it is still helpful and important for you to get a flu shot each year.
Who should think twice about getting vaccinated?
Some people should consult a physician before being vaccinated. They include:
- People who have a severe allergy to chicken eggs. Viruses used in the production of the vaccine are grown in chicken eggs. The flu vaccine may contain some egg protein, which can cause an allergic reaction if you are allergic to eggs.
- People who have had a severe reaction to an influenza vaccination in the past.
- People who developed Guillain-Barré syndrome within six weeks of getting an influenza vaccine in the past (see “What is Guillain-Barré syndrome?” below).
- People who have a moderate or severe illness with a fever. These people should wait until their symptoms improve to get vaccinated. It is fine to get a flu vaccine if you have a mild cold with no fever.
Talk with your doctor if you have questions about whether you should get a flu vaccine.
Flu shot side effects
The most common side effect of a flu shot is soreness at the site of the vaccination. Other side effects, especially in children who have not previously been exposed to the flu virus, include fever, tiredness, and sore muscles. These side effects may begin six to 12 hours after vaccination and can last up to two days. Some people who get fever, tiredness, and sore muscles after getting a flu shot think that the shot gave them the flu. It didn’t give them the flu, however — it gave them side effects.
What is Guillain-Barré syndrome?
Guillain-Barré (pronounced ghee-YAN bah-RAY) syndrome (GBS) is a disease that causes the immune system to attack the nerves, resulting in muscle weakness and sometimes paralysis. GBS can last for weeks or months. Most people eventually recover completely or nearly completely, but some people have permanent nerve damage and about 3% to 5% of people who develop GBS die.
It is thought that GBS is often triggered by an infection. In 1976, a vaccine called the swine flu vaccine was associated with GBS, but only in a small number of cases. Several studies have been done to determine whether other flu vaccines are associated with GBS. If there is a risk, the best evidence suggests it is extremely small. Perhaps one person in every million vaccinated people may be at risk of developing GBS.
GBS follows getting the flu more often than it does getting a flu shot. Since the flu shot is very effective (though not perfect) in preventing the flu, you may actually be protecting yourself against GBS by getting a flu shot. For most people, the benefits of getting the flu vaccine greatly outweigh the small risk of developing GBS. In general, doctors consider the flu vaccine to be very safe and underutilized.