Seasonal Influenza Vaccine Safety: A Summary for Clinicians

CDC and FDA monitor the safety of all vaccines licensed in the United States, including seasonal influenza vaccines. Studies support the safety of annual influenza vaccination in children and adults.

This summary provides information on four types of influenza vaccines:

  • Egg-based inactivated influenza vaccine (egg-based IIV4s)
  • Cell culture-based inactivated influenza vaccine (ccIIV4)
  • Recombinant influenza vaccine (RIV4)
  • Live attenuated influenza vaccine (LAIV4)

Three topic areas are reviewed for each vaccine type:

  • Adverse Event Following Immunization (AEFI): Adverse health events or health problems that occur following or during administration of a vaccine that might be caused by the vaccine or might be coincidental and not related to vaccination.
  • Contraindications: A condition in a vaccine recipient that increases the risk for a serious adverse reaction. A vaccine should not be administered when a contraindication is present.
  • Precautions: A condition in a vaccine recipient that might increase the risk for a serious adverse reaction, might cause diagnostic confusion, or might compromise the ability of the vaccine to produce immunity (e.g., administering measles vaccine to a person with passive immunity to measles from a blood transfusion administered up to 7 months prior). In general, vaccinations should be deferred when a precaution is present. However, a health care provider may determine that vaccination is indicated in the presence of a precaution because the benefit of protection from the vaccine outweighs the risk for an adverse reaction.

Additionally, general vaccine safety information on the following topics appears at the end of this summary:

  • Egg allergies
  • National Vaccine Injury Compensation Program (VICP)
  • Reporting adverse events to the Vaccine Adverse Event Reporting System (VAERS)
  • Additional resources for clinicians

Egg-Based Inactivated Influenza Vaccines (Egg-Based IIV4s)

Egg-based IIV4s are administered by injection. These vaccines are made with influenza viruses that have been grown in eggs and contain very small residual amounts of egg proteins. The viruses are inactivated, and cannot cause influenza.

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Cell Culture-based Inactivated Influenza Vaccine (ccIIV4)

Flucelvax Quadrivalent (cell culture-based quadrivalent inactivated influenza vaccine, ccIIV4) is approved for use in individuals 6 months of age and older.  This vaccine contains influenza vaccines that have been grown in a cell culture instead of in eggs. These viruses have been inactivated and cannot cause influenza.

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Recombinant Influenza Vaccine (RIV4)

RIV4 is administered as an injection.. This vaccine does not contain influenza viruses and cannot cause influenza.

Read more about how recombinant flu vaccines are made.

Live Attenuated Influenza Vaccine (LAIV4)

In clinical trials, quadrivalent LAIV had a safety profile similar to the previously used trivalent LAIV, with the exception of slightly more reports of fever after the first dose of quadrivalent LAIV compared to trivalent LAIV. This occurred in a subset of children 2 years through 8 years of age who were getting vaccinated for the first time. Rhinitis (runny nose) and nasal congestion  [1.1 MB, 26 pages]  occur more commonly after LAIV than IIV or placebo in adults and children.

  • The most common adverse reactions to LAIV  [1.1 MB, 26 pages]  are runny nose or nasal congestion in all ages, fever >100°F in children 2-6 years of age, and sore throat in adults.
  • One study of 8,352 children aged 6 through 59 months showed that younger children aged 6 through 23 months (an age group for which LAIV is not licensed) had increased rates of wheezing in the 42 days after LAIV (6%) than after IIV (4%). Children aged 24 through 59 months had similar rates of wheezing after LAIV (2%)  pdf icon[1.1 MB, 26 pages]external icon  and IIV (3%).
  • According to the LAIV package insert external icon:
    • In children aged 2 through 6 years, fever >100° F occurred more often after first dose LAIV (16%) than placebo (11%). Adults receiving LAIV did not have an increased risk for fever after vaccination compared with placebo.
    • In adults the following other adverse events were reported more often after LAIV than after an intranasal placebo: headache, sore throat, tiredness/weakness, muscles aches, cough, chills, and sinusitis.

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Egg Allergies

People with egg allergies can receive any licensed, recommended age-appropriate influenza vaccine (IIV, RIV4, or LAIV4) that is otherwise appropriate.  People who have a history of severe egg allergy (those who have had any symptom other than hives after exposure to egg) should be vaccinated in a medical setting, supervised by a health care provider who is able to recognize and manage severe allergic reactions, if quadrivalent recombinant vaccine or quadrivalent cell-based vaccine. is not used.

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Reporting Adverse Reactions

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The National Vaccine Injury Compensation Program

The National Vaccine Injury Compensation Program (VICP) is a federal program that was created to compensate people who may have been injured by certain vaccines.

Individuals who believe they may have been injured by a vaccine can learn about the program and about filing a claim by calling 1-800-338-2382 or visiting the VICP website. There is a time limit to file a claim for compensation.