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Influenza (Flu) Vaccines

Addressing Common Questions about Influenza Vaccination for Adults

What disease does flu vaccine protect against? 

Seasonal influenza (flu) vaccines protect against seasonal influenza 

viruses that circulate among people annually. The flu is a contagious 

respiratory disease that spreads around the United States every fall 

and winter, usually beginning in October and lasting as late as May. 

Flu vaccines are made to protect against the three or four different 

flu viruses that research indicates will be most common during the 

upcoming season. 

How common is this disease? 

Flu is very common in the United States in the fall and winter. Millions 

of people get sick, hundreds of thousands are hospitalized, and tens of 

thousands of people die from flu every year.

How is this disease spread? 

Flu is spread mainly by droplets made in the air when people with 

flu cough, sneeze, or talk. A person might also get flu by touching an 

object that has flu virus on it and then touching their own mouth or 

nose. 

Who is at risk for this disease? 

Anyone can get the flu. Even healthy people can get sick with the flu 

and spread it to others. While everyone 6 months of age and older 

should get the flu vaccine each season, it is especially important 

for people who are at increased risk for severe complications 

from influenza. People who are at high risk of developing serious 

complications (like pneumonia) if they get sick with the flu include: 

• People who have certain medical conditions such as asthma or 

other lung disease, diabetes, and heart disease

• Pregnant women 

• Children younger than age 5 years (especially those younger 

than 2 years) 

• Older adults age 65 years and older 

A complete list is available at People Who Are at High Risk of 

Developing Flu-Related Complications (www.cdc.gov/flu/about/

disease/high_risk.htm).

For more information on this and other vaccines

for adults, visit www.cdc.gov/vaccines/adults.

What could happen if I get 

this disease?

Symptoms of flu come on suddenly and may last 

several days. They can include:

• Fever* or feeling feverish/chills

• Sore throat

• Muscle aches

• Fatigue

• Cough

• Headache

• Runny or stuffy nose

* It’s important to note that not everyone with 

 flu will have a fever.

Most people who get the flu will have mild 

illness, will not need medical care or influenza 

antiviral drugs, and will recover in less than 

two weeks. Although severe illness from flu 

infection can occur in persons of all ages, some 

people are more likely to get flu complications 

that result in hospitalization, and occasionally 

death. Pneumonia, bronchitis, sinus infections 

and ear infections are examples of flu-related 

complications. Flu can also worsen illness related 

to heart disease, diabetes, and other chronic 

health problems. For example, people with 

asthma may experience asthma attacks while 

they have the flu, and people with chronic heart 

disease may experience a worsening of this 

condition triggered by flu. 

CS HCVG15-ADU-128 01/18/2017
Addressing Common Questions about Influenza Vaccination for Adults

How does flu vaccine work?

Flu vaccines cause antibodies to develop in the body about two weeks after vaccination. These antibodies provide 

protection against infection with the viruses that are in the vaccine.

The seasonal flu vaccine protects against the influenza viruses that research indicates will be most common during the 

upcoming season. Traditional flu vaccines (called “trivalent” vaccines) are made to protect against three flu viruses; an 

influenza A (H1N1) virus, an influenza A (H3N2) virus, and an influenza B virus. There are also flu vaccines made to protect 

against four flu viruses (called “quadrivalent” vaccines). These vaccines protect against the same viruses as the trivalent 

vaccine and an additional B virus.

Last Updated December 2016

Who should get flu vaccine? When and how often is it 

needed?

Everyone 6 months and older is recommended to get vaccinated against 

influenza every year, including pregnant women. It is best to get vaccinated 

soon after vaccine becomes available each autumn. There are two reasons for 

annual vaccination. First, flu viruses often change, so each year’s flu vaccines 

are made to protect against the flu viruses expected to cause the most illness 

that year. The second reason is because a person’s immune protection from 

vaccination declines over time.

There are several flu vaccine options available during the flu season. Adults 

should talk with their doctors to learn which vaccines are recommended for 

them. The important thing is to get a flu vaccine every year.

Who should not get flu vaccine?

Some adults, including those with a severe 

allergy to any part of the vaccine, should 

not get vaccinated against flu. Some 

people with a history of Guillain-Barré 

Syndrome (a severe paralyzing illness, 

also called GBS) also should not get a flu 

vaccine. People who have a moderateto-severe illness with or without a fever 

should wait until they recover before 

getting vaccinated. 

What are the potential side effects of flu vaccine? 

Different side effects can be associated with flu shots. These side effects are usually mild and short-lasting (1-2 days following 

vaccination), especially when compared with the duration of symptoms from influenza infection. 

Following inactivated (“killed”) or recombinant flu vaccines, some minor side effects that can occur are soreness, redness, or 

swelling where the shot was given, fever (low-grade), and aches. A person cannot get the flu from a flu vaccine. 

If these problems occur, they begin soon after vaccination and are mild and short-lived. Almost all people who receive 

influenza vaccine have no serious problems from it. However, on rare occasions, flu vaccination can cause serious problems, 

such as severe allergic reaction. 

Where can I get the vaccine? 

Adults can get flu vaccine at doctors’ offices, 

pharmacies, workplaces, health clinics, and health 

departments. Check with your doctor or pharmacist 

or use the Adult Vaccine Finder (vaccine.healthmap.

org) to help you find places that provide flu vaccines 

near you. 

How much does the vaccine cost?

Most health insurance, including Medicare, covers flu vaccine. Check 

with your insurance provider for details on whether there is any cost 

to you and for a list of in-network immunization providers. If you do 

not have health insurance or are otherwise not able to afford the flu 

vaccine, contact your local or state health department immunization 

program to find out how you can get the vaccine.

How safe is flu vaccine? 

Over the years, millions of Americans have safely received flu vaccines. CDC and FDA closely monitor the safety of seasonal 

influenza vaccines and other vaccines licensed for use in the United States.

Is it safe to get if I have certain health conditions or am taking prescription meds? 

People who have had a severe (life-threatening) allergy or reaction to a previous flu vaccine should not be vaccinated. 

People who have an allergy to eating eggs should discuss flu vaccination with their doctor. Many gg-allergic 

individuals can safely receive influenza vaccine. It is safe for people taking prescription medications to get flu vaccines.