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Ask the Experts: Influenza

Results (107)

Seasonal influenza epidemics occur predictably each winter, although their timing and severity varies unpredictably. From 2010–11 through 2024–25, CDC estimates that influenza caused 9.4–51 million illnesses, 120,000–710,000 hospitalizations, and 6,300–52,000 deaths annually. CDC’s preliminary estimate for the 2025–26 season was at least 32 million illnesses, 390,000 hospitalizations, and 24,000 deaths in the United States. CDC classified the season as moderate severity overall and high severity among children. As of September 11, 2026, CDC had received reports of 192 influenza-associated pediatric deaths for 2025–26. For more about the burden of influenza, see www.cdc.gov/flu-burden/, and visit CDC’s FluView (www.cdc.gov/fluview/index.html) for weekly updates on influenza activity.

The risks for influenza-related complications, hospitalization, and death are highest among adults age 65 years and older. CDC estimates that adults age 65 and older accounted for 57% of influenza-related hospitalizations during the 2024–25 season. CDC’s final 2024–25 vaccination coverage estimates were 63.8% among adults age 65 years and older, 41.9% among all adults, and 50.2% among children. In the 2023–24 season (the most recent season with an estimate), 20% of hospitalizations and deaths occurred among people age 50 through 64, and vaccination rates in this age group were substantially lower than those age 65 and older. See www.cdc.gov/flu/whats-new/2025-2026-influenza-activity.html and www.cdc.gov/fluvaxview/coverage-by-season/2024-2025.html.

CDC recommends annual influenza vaccination for everyone age 6 months and older who does not have a contraindication as the best way to reduce influenza illness and its potentially serious complications.

Last reviewed: October 11, 2026


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Last reviewed: January 9, 2026

While even healthy children and adults get severe influenza and die from influenza and its complications, the risk of severe influenza is higher for children younger than 5 years, adults 50 years and older, pregnant people, Alaska Natives and American Indians, and residents of nursing homes or other long-term care facilities. Medical conditions that increase a person’s risk of severe influenza include chronic pulmonary (including asthma), cardiovascular (excluding isolated hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders (including diabetes mellitus); immunocompromising conditions due to any cause (including, but not limited to, immune suppression caused by medications or HIV); extreme obesity (body mass index of 40 or greater for adults); and the chronic use of aspirin- or salicylate-containing medications in children through age 18 (due to the risk of Reye syndrome after influenza infection).

More information about risk factors for severe influenza infection can be found at: www.cdc.gov/flu/highrisk/index.htm.

Last reviewed: October 11, 2026

The timing and severity of influenza seasons are unpredictable. Generally, the season falls between October and March, with peak activity most often occurring in January or February in the continental United States. Current information on influenza virus circulation is updated weekly by CDC and available at www.cdc.gov/fluview/.

Last reviewed: October 11, 2026

Information regarding influenza surveillance is available year-round from CDC. For an overview and link to CDC’s influenza surveillance systems, visit www.cdc.gov/fluview/. CDC publishes updated information weekly. In addition, periodic updates about influenza are published in MMWR. CDC also publishes respiratory virus surveillance information that integrates influenza, COVID-19 and RSV on the Respiratory Illness Data Channel at www.cdc.gov/respiratory-viruses/data/index.html.

State and local health departments should be consulted regarding local access to public health influenza vaccination programs and information about state or local influenza activity. Contact state or local health officials to report influenza outbreaks and for guidance in outbreak response.

Last reviewed: October 11, 2026

CDC’s influenza vaccination recommendations from the July 2025 CDC immunization schedules remain in effect for 2026–27, under the terms of the federal court orders halting implementation of votes made by ACIP after its membership was changed in June 2025. CDC continues to recommend annual influenza vaccination for all people without a contraindication, beginning at age 6 months.  

This season, separate seasonal vaccination recommendations for use of influenza, COVID-19, and RSV vaccines were published by the American Academy of Pediatrics (AAP), American Academy of Family Physicians (AAFP), American College of Obstetricians and Gynecologists (ACOG), and the Infectious Diseases Society of America (IDSA). All of the medical societies emphasize the benefits of routine annual influenza vaccination.  

Important 2026–27 updates are summarized below: 

  • All three vaccine virus components changed for 2026–27. All U.S. influenza vaccines remain trivalent, containing two influenza type A strains and one influenza type B strain. 
  • In August 2026, FDA approved mFlusiva (Moderna), the first mRNA influenza vaccine, for people age 50 years and older. 
  • Carrying over last season’s recommendations, CDC recommends high-dose inactivated influenza vaccine (HD-IIV, Fluzone High-Dose by Sanofi), adjuvanted inactivated influenza vaccine (aIIV, Fluad by Seqirus), or recombinant influenza vaccine (RIV, Flublok by Sanofi) preferentially for adults age 65 years and older.  
  • AAFP recommends HD-IIV, aIIV, RIV, or the new mRNA influenza vaccine preferentially for people age 65 and older.  
  • AAP recommends any age-appropriate product for children without preference.  
  • ACOG recommends an age-appropriate IIV or RIV during pregnancy. The live-attenuated influenza vaccine (LAIV, FluMist by AstraZeneca) is not recommended during pregnancy, and the mRNA vaccine is not approved for use during pregnancy because of a lack of data on its use during pregnancy.  
  • IDSA recommends an age-appropriate 2026–27 influenza vaccine for immunocompromised people. AAP and IDSA provide additional details in their guidance documents on the optimal timing of vaccine administration and, in certain circumstances, product choice, for children and adults with significant immunocompromise due to disease or treatment.  
Last reviewed: September 23, 2026

CDC’s current 2026–27 interim clinical considerations are available at www.cdc.gov/flu/hcp/vax-summary/seasonal-influenza-vaccines.html. The version published on September 1, 2026, does not contain information about the mRNA influenza vaccine (mFlusiva by Moderna) which was licensed by FDA on August 5, 2026.  

In the absence of a functional ACIP at CDC during 2026, separate seasonal respiratory virus vaccination recommendations were published by the American Academy of Pediatrics (AAP), American Academy of Family Physicians (AAFP), American College of Obstetricians and Gynecologists (ACOG), and the Infectious Diseases Society of America (IDSA). Their recommendations were informed by the Vaccine Integrity Project (VIP) of the University of Minnesota and the American Medical Association (AMA), which conducted a systematic review of relevant scientific literature published since the previous season’s vaccination recommendations were made. Published studies of the new mFlusiva mRNA influenza vaccine were included in the VIP review. AAP, AAFP, ACOG, and IDSA recommendation documents, plus the published evidence reviews, are all available from the AMA website at www.ama-assn.org/amaone/vaccine-recommendations. 

Last reviewed: September 23, 2026

CDC and relevant medical societies recommend annual influenza vaccination for everyone age 6 months and older who does not have a contraindication to influenza vaccination.

Last reviewed: October 11, 2026

Moderna’s mFlusiva is the first FDA-approved mRNA influenza vaccine. FDA approved it on August 5, 2026, for people age 50 years and older. It is not approved for use during pregnancy due to a lack of data on its use during pregnancy. It is supplied as a preservative-free, single-dose prefilled syringe and is administered as a 0.38 mL intramuscular dose. It is contraindicated for people who have had a severe allergic reaction (e.g., anaphylaxis) to a prior dose of mFlusiva or to a component of the vaccine. It contains no egg protein, preservatives, or antibiotics; it does contain polyethylene glycol (PEG). It is stored at standard temperatures for refrigerated vaccines: 2° to 8°C (36° to 46°F); it should never be frozen. It may be kept at room temperature, at 8° to 25°C (46° to 77°F), for up to 12 hours, but it should not be returned to the refrigerator after room-temperature storage begins. FDA information, including the package insert, is available at www.fda.gov/vaccines-blood-biologics/vaccines/mflusiva.

A large-scale, randomized clinical trial comparing its effectiveness to a standard, egg-based inactivated influenza vaccine (IIV) found it to be moderately superior to standard egg-based IIV, preventing 26.6% more cases of influenza infection in the study population age 50 years and older. This result is similar to the 24.4% relative reduction in influenza infections measured in a randomized clinical trial comparing high-dose influenza vaccine (HD-IIV) to standard, egg-based IIV among adults age 65 years and older that was published in 2014. Side effects, including injection site pain, fatigue, headache, and other systemic symptoms were significantly more common in mFlusiva recipients, but were generally mild and lasted a median of two days. 

A separate study in people age 65 years and older measured a somewhat stronger antibody response to mFlusiva compared to HD-IIV; however, this serologic study did not compare the products’ relative effectiveness at preventing clinical infections.  Further studies of mFlusiva’s clinical effectiveness in people age 65 years and older are planned. 

The September 1, 2026, CDC interim clinical considerations for the use of 2026–27 influenza vaccines are silent on mFlusiva. The American Academy of Family Physicians (AAFP) recommends mFlusiva as one of four preferred options for adults age 65 years and older, based upon the clinical trial evidence of its superior effectiveness against influenza infection compared to standard IIV. View the AAFP 2026–27 season recommendations for COVID-19, influenza, and RSV vaccination of immunocompetent adults and healthcare personnel at www.aafp.org/assets/image/upload/v1788277985/pdf_2026_through_2027_influenza_rsv_sars_covid_2_guidance.pdf.  

Last reviewed: September 23, 2026

Multiple manufacturers are producing inactivated, recombinant, live attenuated, and mRNA influenza vaccines for the U.S. market for the 2026–27 season. All are trivalent. The first mRNA influenza vaccine, mFlusiva by Moderna, was approved by FDA for people age 50 years and older on August 5, 2026.

Find key specifications for each product on Immunize.org’s 1-page influenza vaccine product summary is available at www.immunize.org/catg.d/p4072.pdf.

Last reviewed: October 11, 2026

The 2026–27 vaccines are all trivalent, containing two influenza A and one influenza B strain. All three components changed from 2025–26. Egg-based influenza vaccines include:

  • an A/Missouri/11/2025 (H1N1)pdm09-like virus;
  • an A/Darwin/1454/2025 (H3N2)-like virus; and,
  • a B/Tokyo/EIS13-175/2025 (B/Victoria lineage)-like virus.

Cell culture-based, recombinant, and mRNA vaccines include:

  • an A/Missouri/11/2025 (H1N1)pdm09-like virus;
  • an A/Darwin/1415/2025 (H3N2)-like virus; and,
  • a B/Pennsylvania/14/2025 (B/Victoria lineage)-like virus.

See www.cdc.gov/flu/season/2026-2027.html.

Last reviewed: October 11, 2026

All nine 2026–27 influenza vaccines approved for adults are trivalent.

There are six injectable options for adults: three egg-based standard-dose inactivated influenza vaccines (SD-IIVs), one recombinant influenza vaccine (RIV), one cell culture-based inactivated vaccine (ccIIV), and one mRNA vaccine. All are administered intramuscularly (IM):

  • Fluarix (GSK): 0.5 mL/dose for age 6 months and older
  • FluLaval (GSK): 0.5 mL/dose for age 6 months and older
  • Fluzone (Sanofi): 0.5 mL/dose for adults
  • Flucelvax (ccIIV, CSL Seqirus): 0.5 mL/dose for age 6 months and older
  • Flublok (RIV, Sanofi): 0.5 mL/dose for age 9 years and older
  • mFlusiva (mRNA, Moderna): 0.38 mL/dose for age 50 years and older

One egg-based live attenuated nasal spray vaccine, FluMist (LAIV, AstraZeneca), is an option for healthy, nonpregnant adults through age 49 years: 0.2 mL (given intranasally, 0.1 mL in each nostril).

CDC preferentially recommends three injectable vaccines for adults age 65 years and older:

  • Flublok (RIV, Sanofi): 0.5 mL/dose
  • Fluzone High-Dose (egg-based HD-IIV, Sanofi): 0.5 mL/dose
  • Fluad (egg-based aIIV with MF59 adjuvant, CSL Seqirus): 0.5 mL/dose

The American Academy of Family Physicians (AAFP) includes mFlusiva (mRNA, by Moderna) as a preferred option for adults age 65 years or older. It was licensed in August 2026 for use in adults age 50 years or older. CDC’s clinical considerations published September 2, 2026, did not include information on mFlusiva.

Since 2024, CDC has recommended that solid organ transplant recipients age 18 through 64 years who are taking immunosuppressive medication may receive Fluzone High-Dose or Fluad off-label, without preference over other age-appropriate IIVs or RIV.

Last reviewed: October 11, 2026

CDC recommends any available age-appropriate influenza vaccine for people age 6 months through 64 years. For adults age 65 years and older, CDC preferentially recommends Fluzone High-Dose, Flublok, or Fluad. If none is available, CDC recommends giving any other age-appropriate influenza vaccine rather than delaying vaccination.

AAFP recommends these same three products or mFlusiva (mRNA) preferentially for adults age 65 years and older. For adults age 50 through 64 years, AAFP recommends any age-appropriate product without preference.

CDC recommends that solid organ transplant recipients age 18 through 64 years who are taking immunosuppressive medication may receive Fluzone High-Dose or Fluad off-label, without preference over other age-appropriate IIVs or RIV. See www.cdc.gov/flu/hcp/vax-summary/seasonal-influenza-vaccines.html and www.aafp.org/assets/image/upload/v1788277985/pdf_2026_through_2027_influenza_rsv_sars_covid_2_guidance.pdf.

Last reviewed: October 11, 2026


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Last reviewed: September 3, 2025

CDC and medical societies recommend that most people who need only 1 dose of influenza vaccine be vaccinated ideally in September or October. Continue vaccination after October as long as influenza viruses are circulating and unexpired vaccine is available.

CDC and medical societies recommend avoiding vaccination in July and August for most adults, particularly older adults and pregnant people in the first or second trimester, unless vaccination later might not be possible. Vaccination in July or August may be considered during the third trimester of pregnancy so the newborn may benefit from maternal influenza antibodies transferred before delivery. CDC and the American Academy of Pediatrics (AAP) recommend that children who need 2 doses receive the first dose as soon as vaccine is available so the second dose can be given by the end of October; children who need only 1 dose may also be vaccinated in July or August.

Last reviewed: October 11, 2026


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Last reviewed: September 3, 2025

AAP has developed one-page immunization fact sheets intended to supplement, but not replace, the CDC Vaccine Information Statements (VISs) for vaccines given to children. VISs are required by federal law to be provided for all vaccines covered by the National Vaccine Injury Compensation Program, which includes all vaccines routinely recommended for children or during pregnancy.  

The fact sheets, some of which are available in Spanish, can be downloaded at no cost from the AAP website at  www.aap.org/en/patient-care/immunizations/immunization-fact-sheets/.  

Last reviewed: September 23, 2026

There is no routine recommendation for revaccination later in the season of people who have been fully vaccinated for the season, regardless of when the current season vaccine was received.

Last reviewed: October 11, 2026

Peak influenza activity generally occurs in the Northern Hemisphere during December through March, most frequently in January or February. Providers should continue vaccinating patients through spring, as long as there is continued circulation of influenza viruses and they have unexpired vaccine in stock and unvaccinated patients in their office.

Because influenza occurs in many areas of the world during April through September, vaccine should be given to travelers to areas with influenza activity at that time of year who missed vaccination in the preceding fall and winter. Another late season use of vaccine is for children younger than age 9 years who needed 2 doses of vaccine but failed to get their second dose. For each of these situations, vaccine can be given through the month of June since most injectable influenza vaccine has a June 30 expiration date.

Last reviewed: October 11, 2026


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Last reviewed: September 3, 2025

Yes, influenza vaccines may be coadministered with other recommended vaccines.

The live attenuated nasal spray influenza vaccine (FluMist, LAIV) may be given on the same day as any other live or inactivated vaccines. However, if two live vaccines are not given on the same day, they should be separated by at least 4 weeks.

There are now several vaccines containing nonaluminum adjuvants recommended for adults (including Nuvaxovid [COVID-19], Shingrix [zoster], Heplisav-B [HepB], Arexvy [RSV] and Fluad [aIIV, influenza]). Because of the limited data on the safety or reactogenicity of simultaneous administration of two or more vaccines containing nonaluminum adjuvants and the availability of nonadjuvanted influenza vaccine options, CDC has advised in recent seasons considering a nonadjuvanted influenza vaccine in situations in which influenza vaccine and another vaccine containing a nonaluminum adjuvant are due at the same visit. However, influenza vaccination should not be delayed if a specific brand of vaccine is not available.

Last reviewed: October 11, 2026


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Last reviewed: November 16, 2025

Yes, coadministration of influenza and RSV vaccines at the same visit is acceptable. CDC has provided the details of available information in its guidance on RSV vaccination of older adults: https://www.cdc.gov/vaccines/hcp/by-disease/rsv.html#cdc_vaccine_product_information_section_3-rsv-vaccination-for-adults.

CDC advises that when deciding whether or not to coadminister other vaccines with an RSV vaccine, consider whether the patient is up to date with currently recommended vaccines, the feasibility of the patient returning for additional vaccine doses, their risk for acquiring vaccine-preventable disease, vaccine reactogenicity profiles, and patient preferences.

Last reviewed: October 11, 2026

Yellow fever vaccine is contraindicated for people who have a history of a severe (anaphylactic) allergy to eggs.

CDC and medical societies issuing vaccination recommendations do not consider egg allergy of any severity to be a contraindication or precaution to egg-based influenza vaccines. A person with egg allergy of any severity may receive any influenza vaccine that is appropriate for the person’s age and health status. When administering an egg-based influenza vaccine to a person with egg allergy of any severity, no additional safety precautions are needed, beyond those recommended when administering any vaccine to any recipient. 
 

Last reviewed: September 23, 2026

CDC recommends that U.S. travelers who are at higher risk for influenza complications and who were not vaccinated with influenza vaccine during the previous Northern Hemisphere fall or winter should consider receiving influenza vaccination before departure if they plan to travel to the tropics, to the Southern Hemisphere during the Southern Hemisphere influenza season (April–September), or with organized tourist groups or on cruise ships to any location. Those traveling in large groups, through large airports, and on cruise ships may encounter people from all over the world, including those from areas where influenza is circulating.

Last reviewed: October 11, 2026

There should be a minimum of 4 weeks between the doses in such situations.

Last reviewed: October 11, 2026

Because more than one type or subtype of influenza virus can circulate in any given influenza season, healthcare providers should offer influenza vaccination to unvaccinated people throughout the influenza season, including people who may have had an influenza illness already in the season. Infection with one influenza virus does not protect against infections with other circulating types. Vaccination helps protect against two different Type A influenza viruses and one Type B virus each year.

Last reviewed: October 11, 2026


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Last reviewed: January 9, 2026

Protection from influenza vaccine wanes after vaccination (the amount of protection and the speed of waning varies by strain and by recipient age) but generally persists for at least 5–6 months.

Last reviewed: October 11, 2026

First, injectable influenza vaccines cannot cause influenza because they contain only parts of the virus. The live attenuated nasal spray vaccine is modified so that it cannot cause influenza because it cannot replicate at human body temperature. Fewer than 1% of vaccinated people might develop flu-like symptoms, such as mild fever and muscle aches, after vaccination. These vaccine side effects are not the same as having influenza, but people may confuse the side effects with illness.

Other reasons a person might have had influenza illness or an illness that they thought might be “the flu” after vaccination include:

  • Protective immunity doesn’t develop until 1–2 weeks after vaccination. Some people who get vaccinated after influenza viruses are already circulating may be infected with influenza before the vaccination can stimulate protective immunity.
  • For many people, “the flu” is any illness with fever, cold symptoms or gastrointestinal symptoms. If they get any viral illness, they may blame it on influenza vaccine or think they got “the flu” despite being vaccinated. Influenza vaccine only protects against specific influenza viruses, not all viruses.
  • Vaccinated people can get influenza illness despite vaccination. Influenza vaccination is our best available protection against influenza disease; however, vaccination reduces the risk of infection, it does not prevent all infections.

Vaccine effectiveness (VE) varies by age and by season, depending upon the circulating viruses. In most recent seasons, influenza vaccination has reduced the risk of illness by between roughly 40% and 60% in the vaccinated population (including all ages) during seasons when most circulating influenza viruses are well-matched to the vaccine. VE is generally lower for adults age 65 years and older. Influenza vaccination has also been shown to reduce influenza disease severity even if someone does get sick after vaccination, and vaccination reduces the risk of influenza hospitalization and deaths in children and adults. Influenza vaccination also reduces the risk of stroke and acute cardiac events, like heart attack and heart failure, among people with heart disease.

For more information on this topic, go to: www.cdc.gov/flu-vaccines-work/index.html.

Last reviewed: October 11, 2026

Giving patients an influenza VIS is mandatory under the National Childhood Vaccine Injury Act of 1986. The VIS must be given to all adults as well as to parents or guardians of children prior to vaccination. Two VISs are available, one for live attenuated influenza vaccine (LAIV) and one for inactivated influenza vaccine (IIV) and recombinant vaccine (RIV). The IIV and RIV VIS and all of its translations are available here: www.immunize.org/vaccines/vis/influenza-inactivated/. The LAIV VIS and all of its translations are available here: www.immunize.org/vaccines/vis/influenza-live/. Current influenza vaccine VISs are dated January 31, 2025. No specific VIS is available for mRNA influenza vaccine (mFlusiva) at this time.  
 
Immunize.org also offers a printable PDF document with QR codes for easy access to all of the IIV and RIV influenza vaccine VIS translations: www.immunize.org/wp-content/uploads/catg.d/p2092.pdf. Healthcare providers or recipients can scan the codes to access a digital copy of the translation on their mobile device. 

Last reviewed: September 23, 2026

The most important factor in preventing outbreaks is annual vaccination of all residents and staff who work at facilities such as nursing homes, assisted living facilities, and other group living situations. Groups that should be targeted include physicians, nurses, and other personnel working or volunteering in hospitals and outpatient settings who have contact with high-risk patients in all age groups, and providers of home care to high-risk people (for example, visiting nurses, therapists, and volunteers).

Last reviewed: October 11, 2026

If a patient or family member cannot remember if the patient received influenza vaccine this season and no record is available, proceed with administering influenza vaccine, even if it might mean an extra dose is given. When a patient reports that they HAVE received influenza vaccine but does not have written documentation, ACIP states that in the specific case of influenza (and pneumococcal polysaccharide) vaccination, patient self-report of being vaccinated can be accepted as evidence of vaccination.

Last reviewed: October 11, 2026

FluMist (LAIV, AstraZeneca) is currently approved by FDA only for healthy non-pregnant people age 2 through 49 years. Beginning in the 2025–26 season, FluMist is approved for home use, to be administered to oneself (if age 18 or older) or by a caregiver to a child (if age 2 through 17 years). Home use does not require a visit to a healthcare provider. Details about the home-use program, including self-screening, online ordering, and home administration are available from www.flumist.com.

Last reviewed: October 11, 2026

No. Giving FluMist (LAIV) is not considered an aerosol-generating procedure.

Last reviewed: October 11, 2026

The vaccine dose (0.2 mL) comes inside a special sprayer device. A plastic clip on the plunger divides the dose into two equal parts. The recipient is seated in an upright position with head tilted back. Half of the contents of the sprayer (0.1 mL) is sprayed into each nostril.

Immunize.org offers a 1-page clinic resource demonstrating how to administer intramuscular or intranasal influenza vaccines in a clinic setting: www.immunize.org/wp-content/uploads/catg.d/p2024.pdf.

Last reviewed: October 11, 2026

Yes, unless clinical judgment suggests nasal congestion is present that might keep the vaccine from making good contact with the nasopharyngeal mucosa. In that case, consider either deferring its use until the congestion resolves or using an appropriate alternative influenza vaccine, if available.

Last reviewed: October 11, 2026

Yes. Breastfeeding is not a contraindication for any routine vaccination including FluMist (LAIV).

Last reviewed: October 11, 2026

With rare exceptions, yes. Like other live vaccines, FluMist (LAIV) should not be administered to immunosuppressed people. ACIP has long stated a preference for using injectable influenza vaccine for all close contacts of severely immunosuppressed individuals during those periods in which the immunosuppressed person requires care in a protective environment because of the theoretical risk that the live attenuated vaccine virus could be transmitted to the severely immunosuppressed individual and cause disease. No organization recommends LAIV in that circumstance. Healthcare personnel or other people who have close contact with people with lesser degrees of immunosuppression (people who do not require a protective environment such as reverse isolation in a hospital setting) who are otherwise eligible for FluMist may receive it. No special precautions need to be taken by the vaccinated person.

Last reviewed: October 11, 2026

People should avoid contact with any person who is severely immunosuppressed for at least 7 days after receiving FluMist (LAIV). There are no restrictions on being in contact with any other patients.

Last reviewed: October 11, 2026

Asthma is a precaution, not a contraindication, for FluMist (LAIV) in people 5 years of age and older. FluMist is contraindicated for children 2 through 4 years old who have had a diagnosis of asthma or whose parents or caregivers report that a health care provider has told them during the preceding 12 months that their child had wheezing or asthma or whose medical record indicates a wheezing episode has occurred during the preceding 12 months.

Last reviewed: October 11, 2026

An antiviral drug active against influenza virus may reduce the effectiveness of FluMist by interfering with the vaccine viruses’ ability to replicate in the upper airway in order to produce protective immunity. To prevent interference, CDC and medical societies recommend different intervals between the last dose of an antiviral medication and FluMist administration, based upon the half-life of the antiviral medication. The recommendations are as follows:

  • Oseltamivir or zanamivir: wait at least 48 hours after the last dose before administering FluMist
  • Peramivir: wait at least 5 days before administering FluMist
  • Baloxavir: wait at least 17 days before administering FluMist

If any influenza antiviral medication must be given within 14 days after FluMist administration, the patient should be revaccinated without delay with any age-appropriate injectable influenza vaccine. Inactivated influenza vaccines (IIVs) and recombinant influenza vaccine (RIV) may be administered at any time relative to antiviral medication.

Last reviewed: October 11, 2026

A half dose of FluMist (or any other vaccine) is a non-standard dose and generally should not be counted. If you were unable to give the second half of the vaccine on the same day, you will have to provide another full dose of influenza vaccine at another time. If you want to give FluMist again, you should wait four weeks because it is a live vaccine. Alternatively, you can give an injectable influenza vaccine any time after this partial dose.

Last reviewed: October 11, 2026

CDC and the American Academy of Pediatrics (AAP) recommend annual influenza vaccination for all children age 6 months and older who do not have a contraindication. AAP recommends any licensed vaccine appropriate for the child’s age and health status, without preference for one product or formulation. See the 2026 AAP policy statement on influenza immunization at https://doi.org/10.1542/peds.2026-078778.

Last reviewed: October 11, 2026

All six 2026–27 influenza vaccines approved for children are trivalent. Five injectable vaccines are available for children: three egg-based IIVs, one cell culture-based IIV, and one recombinant vaccine. All are administered intramuscularly:

  • Fluarix (GSK): 0.5 mL/dose for age 6 months and older
  • FluLaval (GSK): 0.5 mL/dose for age 6 months and older
  • Fluzone (Sanofi): 0.25 mL or 0.5 mL per dose for age 6 through 35 months; 0.5 mL/dose for age 3 years and older
  • Flucelvax (ccIIV, CSL Seqirus): 0.5 mL/dose for age 6 months and older
  • Flublok (RIV, Sanofi): 0.5 mL/dose for age 9 years and older
  • One egg-based live attenuated nasal spray vaccine, FluMist (LAIV, AstraZeneca), is an option for healthy, nonpregnant people age 2 years and older: 0.2 mL intranasally.

AAP recommends any licensed influenza vaccine appropriate for the child’s age and health status, without preference for one product or formulation. See AAP’s 2026 influenza vaccine policy statement at https://doi.org/10.1542/peds.2026-078778.

Last reviewed: October 11, 2026

Children age 6 months through 8 years should receive a second influenza vaccine dose 4 weeks or more after the first dose if they meet one of the following three criteria: 1) they are receiving influenza vaccine for the first time, or 2) they have not received a total of at least two doses of any seasonal influenza vaccine before July 1 of the current year, or 3) their vaccination history is unknown. The two previous doses need not have been received during the same season or consecutive seasons.

A child who is 8 years old and is recommended to receive two doses during the current season and turns 9 during the current season before receiving dose 2, should still receive dose 2.

Immunize.org’s handout titled “Guide for Determining the Number of Doses of Influenza Vaccine to Give to Children Age 6 Months Through 8 Years” provides additional guidance on this issue; it is available at www.immunize.org/catg.d/p3093.pdf.

Last reviewed: October 11, 2026

Yes. Doses of FluMist administered in past seasons can be counted.

Last reviewed: October 11, 2026

The two doses may be the same or different products.

Last reviewed: October 11, 2026

The child should receive the dose appropriate for the child’s age at the time of the visit. At age 37 months, give a 0.5 mL dose of Fluzone.

Last reviewed: October 11, 2026

Yes, unless state law prohibits it. Fluzone is the only product in the 2026-27 season that has a multidose vial packaging option containing thimerosal. A June 2025 ACIP vote to recommend only thimerosal-free influenza vaccines was paused by a federal court stay in March 2026 and is not in effect. The American Academy of Pediatrics (AAP) recommends any licensed influenza vaccine appropriate for a child’s age and health status, without preference for a product or formulation. See the 2026 AAP influenza policy statement at https://doi.org/10.1542/peds.2026-078778.

Last reviewed: October 11, 2026

Yes, but only if the 9-year-old meets all of the criteria below:

  • they turned 9 years old during the current season, and
  • they had received one dose during the current season before turning 9, and
  • they have no or unknown history of receiving any previous dose of influenza vaccine before July 1 of the year of the current season.
Last reviewed: October 11, 2026

A CDC study showed a small increased risk for febrile seizures during the 24 hours after a child receives the inactivated influenza vaccine at the same time as the PCV13 vaccine or DTaP vaccine. However, the risk of febrile seizure with any combination of these vaccines is small and ACIP recommends giving these vaccines at the same visit if indicated. The risk for febrile seizures in children who received the currently recommended PCV15 or PCV20 vaccines at the same time as an influenza vaccine has not been studied.

See www.cdc.gov/vaccine-safety/about/febrile-seizures.html for more information about febrile seizures after vaccination.

Last reviewed: October 11, 2026

Yes. Influenza vaccination is especially important during pregnancy because pregnant people are at increased risk for influenza-related complications and infants are at increased risk during the first 6 months of life.

CDC and the American College of Obstetricians and Gynecologists (ACOG) recommend influenza vaccination during any trimester. An age-appropriate inactivated or recombinant influenza vaccine as soon as it is available; FluMist (LAIV) should not be given during pregnancy. ACOG and CDC recommend that vaccination during July or August may be considered during the third trimester, and vaccination should continue while influenza viruses are circulating. The American Academy of Pediatrics (AAP) recommends annual influenza vaccination for all children age 6 months and older, including pregnant adolescents. See ACOG’s 2026 clinical guidance for influenza vaccination www.acog.org/clinical/clinical-guidance/practice-advisory/articles/2025/08/influenza-in-pregnancy-prevention-and-treatment and AAP’s 2026 influenza vaccination policy statement at https://doi.org/10.1542/peds.2026-078778.

Last reviewed: October 11, 2026


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Last reviewed: January 9, 2026


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Last reviewed: September 3, 2025

CDC and the American Academy of Obstetricians and Gynecologists (ACOG) recommend influenza vaccination during any trimester because pregnant people are at increased risk for influenza complications and hospitalization. Infants younger than age 6 months are too young to be vaccinated. Vaccination during pregnancy produces antibodies that cross the placenta and help protect the infant during the first months of life. CDC and ACOG recommend an age-appropriate inactivated or recombinant influenza vaccine during pregnancy. See ACOG’s clinical practice guidance for vaccination at www.acog.org/clinical-information/maternal-immunization-schedule.

Last reviewed: October 11, 2026

CDC, the American Academy of Pediatrics (AAP) and the American College of Obstetricians and Gynecologists (ACOG) recommend any age-appropriate inactivated or recombinant influenza vaccine during pregnancy and recommend against FluMist because it is a live vaccine. The newest influenza vaccine, mFlusiva by Moderna (an mRNA platform vaccine) is approved for use in people age 50 years and older. It is not licensed or recommended for use during pregnancy because of an absence of data on its use during pregnancy.

A June 2025 ACIP vote to recommend only thimerosal-free influenza vaccines was paused by a federal court stay in March 2026 and is not in effect. See ACOG’s clinical practice guidelines for immunization at www.acog.org/clinical-information/maternal-immunization-schedule. See AAP’s 2026 influenza vaccination policy statement https://doi.org/10.1542/peds.2026-078778.

Last reviewed: October 11, 2026

Yes. A June 2025 ACIP vote to recommend only thimerosal-free influenza vaccines was paused by a federal court stay in March 2026 and is not in effect. Among 2026–27 influenza products, only Fluzone has a packaging option of a multidose vial containing thimerosal. The American College of Obstetricians and Gynecologists (ACOG) and the American Academy of Pediatrics (AAP) recommend an age-appropriate inactivated or recombinant influenza vaccine during pregnancy without a preference based on thimerosal. A few states restrict its use during pregnancy; check current state requirements.

Last reviewed: October 11, 2026

No. CDC and medical societies do not routinely recommend more than one dose of influenza vaccine per season, except for certain children being vaccinated for the first time.

Last reviewed: October 11, 2026

A CDC-funded study found that people who had been vaccinated early in pregnancy with an influenza vaccine containing the pandemic H1N1 (H1N1pdm09) component and who also had been vaccinated the prior season with an H1N1pdm09-containing influenza vaccine had an increased risk of spontaneous abortion (miscarriage) in the 28 days after vaccination. This study did not quantify the risk of miscarriage and did not prove that influenza vaccine was the cause of the miscarriage. Earlier studies have not found a link between influenza vaccination and miscarriage. A larger follow-up study also funded by CDC which included 3 more years of data found no association between early miscarriage and influenza vaccination regardless of previous influenza season vaccination. These results are reassuring regarding the safety of influenza vaccination during pregnancy.

CDC, the American Academy of Pediatrics (AAP), and the American College of Obstetricians and Gynecologists (ACOG) all recommend influenza vaccination during any trimester of pregnancy. Influenza poses a danger during pregnancy and the vaccine can prevent influenza in pregnant people and their infants.

Last reviewed: October 11, 2026

The American Academy of Pediatrics (AAP) recommends any licensed influenza vaccine appropriate for a child’s age and health status, without preference for a product or formulation with or without thimerosal. A June 2025 ACIP vote to recommend only thimerosal-free influenza vaccines was paused by a federal court stay in March 2026 and is not in effect. Some states restrict thimerosal-containing vaccines; check current state requirements.

Last reviewed: October 11, 2026

People with a metabolic disease, including diabetes, should receive annual influenza vaccination with an age-appropriate inactivated, mRNA, or recombinant influenza vaccine.

Last reviewed: October 11, 2026

Yes. People with multiple sclerosis should be vaccinated against influenza. Multiple sclerosis is not a contraindication to any vaccine, including influenza vaccines.

Last reviewed: October 11, 2026

Although some studies have demonstrated a transient increase in replication of HIV following inactivated influenza vaccine, other studies have not found this. This temporary increase in HIV titer has not been associated with deterioration in either T-lymphocyte counts or clinical condition. Annual influenza vaccination with an age-appropriate injectable influenza vaccine benefits HIV-infected people.

Last reviewed: October 11, 2026

In November 2015, FDA licensed Fluad (aIIV, CSL Seqirus), an MF59-adjuvanted inactivated influenza vaccine, for people age 65 years and older. Fluad is the first adjuvanted influenza vaccine marketed in the U.S. An adjuvant is a substance added to a vaccine to increase the immune response to vaccination. The MF59 adjuvant is based on squalene, an oil that occurs naturally in many plants and animals. Fluad has been used in Europe since 1997 and is approved in many other countries. In contrast to Fluzone High-Dose (HD-IIV, Sanofi), Fluad is a standard-dose vaccine, containing 15 mcg of hemagglutinin per virus per dose.

Last reviewed: October 11, 2026

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