Flu Vaccine FAQs

What is a flu vaccine? 

The standard flu vaccine is made from flu viruses that have been grown on fertilized chicken eggs. The viruses are killed during manufacturing, a process known as “inactivation.” These inactivated viruses provide proteins or antigens that trigger a protective antibody response when the vaccine is injected into the arm or thigh muscle. Antibodies against flu viruses begin to appear one to two weeks after getting the flu shot and last for months, and sometimes even up to one year. 

Important Note: For most people aged 6 months and older, the standard flu vaccine is the primary option that will be offered at Sutter facilities.

Other flu vaccines will also be available to certain patients:

• Adjuvanted (enhanced) flu vaccine: This flu vaccine includes an “adjuvant” that helps create a stronger immune response to vaccination compared to the standard flu vaccine. It’s approved and preferentially recommended by the CDC for people 65 or older, and is similar to the “high dose” flu vaccine.
• FluMist: This is an egg-based influenza vaccine that is administered as a nasal spray and made with attenuated (weakened) live influenza viruses, which is approved for use in people 2 years through 49 years. This vaccine is not recommended for pregnant people, immunocompromised people or people with certain medical conditions.  
• There are also two egg-free vaccines: Flucelvax (approved for those 6 months and older) and Flublok (approved for those 9 years and older), which are alternative options for patients with a history of severe allergic reaction to previous doses of an egg-containing flu vaccine.

Because vaccine strains often change from one year to the next and immunity wanes, flu vaccine must be given every year.

All flu vaccines offered at Sutter Health are free of thimerosal and latex. 

Who should get a flu vaccine and when?

The easy answer is that almost everyone six months of age and older should get the flu vaccine. Ideally, you should get the vaccine in September or October, but you can be vaccinated throughout the flu season. Additionally, some children 6 months through 8 years of age may need 2 doses for the best protection. Special efforts should be made to vaccinate the following people because they are either at risk for complications from the flu, or they might give the flu to someone who is at risk: 

• Women who are or will be pregnant during the flu season and those up to two weeks post-partum.
• Children younger than five years, especially children ages six months to two years.
• Children on chronic aspirin therapy.
• Adults 50 years and older.
• Persons who are morbidly obese.
• Native American and Alaskan natives.
• People of any age with certain chronic medical conditions.  
• People who live in nursing homes and other long-term care facilities.
• People who live with or care for those at high risk for complications from flu, including: healthcare workers, household contacts of persons at high risk for complications from the flu and household contacts and out-of-home caregivers of children less than 6 months of age (who are too young to be vaccinated). 

Who should not get the flu vaccine? Who should proceed with caution?

Flu vaccine is extremely safe for the vast majority of people, including breastfeeding and pregnant women.

However, some groups should exercise caution: 

• People with a history of severe allergic reaction to the flu vaccine or its components. An egg allergy does not indicate additional safety measures for flu vaccination beyond those recommended for any recipient of any vaccine, regardless of severity of previous reaction to egg.
• Anyone with moderate to severe acute illness, until the illness resolves.
• Children under six months of age, because the vaccine is ineffective in this age group. (Instead, their household contacts and caretakers should get vaccinated).
• People with a history of Guillain-Barre syndrome, until they consult their doctor. 

What are the side effects of the flu vaccine?

The flu vaccine rarely causes serious adverse effects. Most commonly, you may experience mild soreness at the site of injection. Flu-like symptoms, such as fever and muscle aches, occasionally occur six to 12 hours after receiving the flu shot and last one to two days. However, these symptoms are very rare.

Guillain-Barre syndrome — a temporary, acute paralytic illness — was linked to the swine flu vaccine of 1976. But since 1976, studies have failed to show a similar association between flu vaccines and Guillain-Barre. It is estimated that at most one case of Guillain-Barre per million people vaccinated may be attributable to the flu vaccine. By comparison, the flu itself causes many hospitalizations and deaths each year, and influenza can directly cause Guillain-Barre. However, anyone who has had Guillain-Barre in the past within six weeks of flu vaccination should speak with their physician before getting the flu shot.

For more information, visit the CDC website.