Influenza (Flu) Vaccine Safety

Key points

  • Influenza (flu) is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs.
  • You can protect against severe flu illness with vaccination.
  • CDC continuously monitors the safety of flu vaccines using several different safety systems.

Overview

Influenza (flu) can be a mild or severe illness, and its complications can result in hospitalization or death. Some people are at a higher risk for developing serious flu complications, including older adults, young children, and people with certain health conditions. You can protect against severe flu illness with vaccination. CDC, working with FDA and other federal agencies, continuously monitors flu vaccines using several safety systems.

Available vaccines

CDC recommends annual flu vaccination for everyone ages 6 months and older.

Types of flu vaccines

There are two types of flu vaccines for use in the United States: injectables and nasal spray.

Injectables

Injectables include inactivated influenza vaccines [IIV], high-dose IIV, adjuvanted flu vaccines [aIIV], cell-based flu vaccines [ccIIV], and recombinant flu vaccines [RIV].

Injectable flu vaccines do not contain live flu viruses.

Keep Reading: Vaccine Information Statement: Inactivated or Recombinant Shot

Nasal spray (live, attenuated influenza vaccine [LAIV])

Nasal spray flu vaccines use attenuated (weakened) live flu viruses, ensuring they do not cause the flu.

Keep Reading: Vaccine Information Statement: Live, Intranasal Spray

Keep in mind

Health authorities do not prefer one flu vaccine over another; they recommend administering any age-appropriate flu vaccine. Each year, experts review and update the makeup of U.S. flu vaccines to match circulating flu viruses. Multiple manufacturers offer FDA-licensed flu vaccines for use during any flu season. CDC prioritizes high-quality vaccine safety research and identification of adverse events (any side effect or health problem after vaccination that is concerning to you, even if you are not sure if the vaccine caused the event) through public health surveillance. CDC regularly shares vaccine safety monitoring findings and concerns with other federal agencies, the public, healthcare providers, vaccine manufacturers, and advisory committees like the Advisory Committee on Immunization Practices (ACIP).

For children and adults

FDA has approved the following flu vaccines for children and adults:

For people ages 65 years and older

FDA has approved the following flu vaccines for people ages 65 years and older:

Who should & should not get the vaccine

CDC recommends annual flu vaccination for everyone ages 6 months and older with any flu vaccine licensed by FDA that is appropriate for the recipient's age and health status. Vaccination is particularly important for people who are at high risk of developing serious complications from the flu. See information for:

Keep Reading: Who Needs a Flu Vaccine

Common side effects

Vaccines, like any medical product, can have side effects. Many people who get an annual flu vaccine report no side effects at all. Most side effects reported after flu vaccination are mild and disappear on their own in a few days without treatment.

Injectables (inactivated influenza vaccine [IIV] and recombinant influenza vaccine [RIV])

  • Injection site reactions that include soreness, redness, and swelling at the injection site
  • Fever
  • Muscle Aches
  • Headache
  • Fatigue
Keep Reading: Inactivated Influenza VIS

Nasal spray (live, attenuated influenza vaccine [LAIV])

In children

  • Runny nose
  • Wheezing
  • Headache
  • Vomiting
  • Muscle aches
  • Fever (low grade)

In adults

  • Runny nose
  • Headache
  • Sore throat
  • Cough
Keep Reading: Live, Intranasal Influenza VIS

When to call 911

Severe allergic reactions following vaccination are rare but can be life threatening. If someone shows signs of a severe allergic reaction — such as hives, swelling of the face and throat, or difficulty breathing — call 911.

A closer look at the safety data

Fact

Findings from vaccine safety monitoring systems and scientific studies have shown that flu vaccines have an excellent safety profile. Hundreds of millions of Americans have safely received flu vaccines for more than 50 years. The body of scientific evidence overwhelmingly supports their safety.

CDC and FDA monitor the safety of flu vaccines. FDA must license the vaccine, and it must be appropriate for the recipient's age and health status before it can be made available for public use. Below, you will find additional safety information on Guillain-Barré Syndrome, maternal and infant safety, febrile seizures, and narcolepsy.

Guillain-Barré Syndrome (GBS)

The data on an association between seasonal inactivated influenza vaccine and GBS varies from season to season. When there has been an increased risk, it has been in the range of 1-2 additional GBS cases per million flu vaccine doses administered. The data also show that a person is more likely to get GBS after flu disease than after getting a flu vaccine.

Keep Reading: Vaccines and Guillain-Barré Syndrome (GBS)

Maternal and infant safety

Several studies support the safety of flu vaccination during pregnancy.

  • Using the Vaccine Safety Datalink (VSD), CDC conducted a study on the long-term outcomes of infants born to mothers who were vaccinated with tetanus, diphtheria, and acellular pertussis (Tdap) vaccine during pregnancy. The study also included mothers who received the flu vaccine while pregnant. The study found that flu and Tdap vaccines during pregnancy were not associated with an increased risk of hospitalization in infants during the first six months of life. Additionally, there was no increased risk of death in infants during this period.1
  • CDC and other scientific institutions have conducted multiple studies that have examined the risk of miscarriage following flu vaccination. The extensive body of evidence does not suggest a link between flu vaccination and miscarriage.234
Keep Reading: Flu & Pregnancy

Febrile seizure

A CDC study showed that children ages 6–23 months had an increased risk for febrile seizure after simultaneously receiving trivalent inactivated influenza vaccine (IIV3) and pneumococcal conjugate vaccine (PCV). The increased risk was also observed when IIV3 was given with diphtheria-tetanus-acellular pertussis vaccine (DTaP). However, the absolute risk of febrile seizure associated with these vaccine combinations was small.5

Keep Reading: Vaccines and Febrile Seizures

Narcolepsy after the 2009 H1N1 pandemic influenza vaccine

In response to the events in Europe, CDC reviewed data from the Vaccine Adverse Event Reporting System (VAERS) and the Vaccine Safety Datalink (VSD) and found:

  • There was no indication of any association between U.S.-licensed H1N1 or seasonal flu vaccine and narcolepsy.
  • Flu vaccines containing the 2009 H1N1 virus strain used in the United States did not increase the risk for narcolepsy.6

Another study including data from different countries found no associations between adjuvanted pH1N1 vaccines (arenaprix-AS03, Focetria-MF59, and Pandemrix-AS03) and narcolepsy.7

Keep Reading: Historical Vaccine Concerns

How CDC monitors vaccine safety

CDC and FDA are committed to monitoring the safety of vaccines. Once vaccines are licensed or authorized by FDA for use in the United States, CDC, FDA, and other federal agencies work together to monitor them using several safety systems.

Keep Reading: About CDC's Vaccine Safety Monitoring Program

Report possible adverse events to VAERS

The Vaccine Adverse Event Reporting System (VAERS) is an early warning system co-managed by CDC and FDA that monitors for potential vaccine safety problems. Healthcare providers and vaccine manufacturers are required to report specific adverse events (any side effect or health problem after vaccination that is concerning to you, even if you are not sure if the vaccine caused the event) following vaccination to VAERS, including those listed by the manufacturer as contraindications (a reason not to get more doses of a vaccine). Patients and caregivers can also submit reports to VAERS. Submitting a Vaccine Adverse Event Reporting System (VAERS) Report and Using VAERS Data

Submitting a Vaccine Adverse Event Reporting System (VAERS) Report and Using VAERS Data

Resources

Clinical Guidance for Seasonal Influenza Vaccine Safety
CDC and FDA monitor the safety of all vaccines licensed in the United States, including flu vaccines
Guillain-Barré Syndrome and Flu Vaccine
Guillain-Barré syndrome (GBS) is a rare disorder in which a person’s own immune system damages their...
Thimerosal in Flu Vaccine
Thimerosal is an ethyl mercury-based preservative used in vials that contain more than one dose of a...
Thimerosal in Flu Vaccine
Thimerosal is an ethyl mercury-based preservative used in vials that contain more than one dose of a...
Contraindications and Precautions
Contraindications and Precautions: General Best Practice Guidelines for Immunization. Advisory Commi...
Vaccines & Immunizations
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Content Source:
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)
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  2. Donahue, J. G., Kieke, B. A., King, J. P., Mascola, M. A., Shimabukuro, T. T., DeStefano, F., Hanson, K. E., McClure, D. L., Olaiya, O., Glanz, J. M., Hechter, R. C., Irving, S. A., Jackson, L. A., Klein, N. P., Naleway, A. L., Weintraub, E. S., & Belongia, E. A. (2019). Inactivated influenza vaccine and spontaneous abortion in the Vaccine Safety Datalink in 2012-13, 2013-14, and 2014-15. Vaccine, 37(44), 6673–6681. https://doi.org/10.1016/j.vaccine.2019.09.035
  3. Donahue, J. G., Kieke, B. A., King, J. P., DeStefano, F., Mascola, M. A., Irving, S. A., Cheetham, T. C., Glanz, J. M., Jackson, L. A., Klein, N. P., Naleway, A. L., Weintraub, E., & Belongia, E. A. (2017). Association of spontaneous abortion with receipt of inactivated influenza vaccine containing H1N1pdm09 in 2010-11 and 2011-12. Vaccine, 35(40), 5314–5322. https://doi.org/10.1016/j.vaccine.2017.06.069
  4. Irving, S. A., Kieke, B. A., Donahue, J. G., Mascola, M. A., Baggs, J., DeStefano, F., Cheetham, T. C., Jackson, L. A., Naleway, A. L., Glanz, J. M., Nordin, J. D., Belongia, E. A., & Vaccine Safety Datalink (2013). Trivalent inactivated influenza vaccine and spontaneous abortion. Obstetrics and gynecology, 121(1), 159–165. https://doi.org/10.1097/aog.0b013e318279f56f
  5. Duffy, J., Weintraub, E., Hambidge, S. J., Jackson, L. A., Kharbanda, E. O., Klein, N. P., Lee, G. M., Marcy, S. M., Nakasato, C. C., Naleway, A., Omer, S. B., Vellozzi, C., DeStefano, F., & Vaccine Safety Datalink (2016). Febrile Seizure Risk After Vaccination in Children 6 to 23 Months. Pediatrics, 138(1), e20160320. https://doi.org/10.1542/peds.2016-0320
  6. Weibel, D., Sturkenboom, M., Black, S., de Ridder, M., Dodd, C., Bonhoeffer, J., Vanrolleghem, A., van der Maas, N., Lammers, G. J., Overeem, S., Gentile, A., Giglio, N., Castellano, V., Kwong, J. C., Murray, B. J., Cauch-Dudek, K., Juhasz, D., Campitelli, M., Datta, A. N., Kallweit, U., ... Shimabukuro, T. T. (2018). Narcolepsy and adjuvanted pandemic influenza A (H1N1) 2009 vaccines - Multi-country assessment. Vaccine, 36(41), 6202–6211. https://doi.org/10.1016/j.vaccine.2018.08.008
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