Ask the Experts: Influenza

Results (96)

Influenza is the second most frequent cause of death from a vaccine-preventable disease in the United States after COVID-19. Rates of infection from seasonal influenza are highest among children, but the risks for complications, hospitalizations, and deaths are higher among adults age 65 years and older, children younger than 5 years, pregnant individuals, and people of any age who have medical conditions that place them at increased risk for complications from influenza.

From the 2010–11 through the 2022–23 seasons (excluding 2020–2021, when COVID-19 control measures resulted in almost no influenza activity), the annual influenza-related disease burden has varied from approximately 9 to 41 million illnesses, 4 to 21 million medical visits, 140,000 to 810,000 hospitalizations and 12,000 to 61,000 deaths per year, including an average of 129 pediatric deaths reported to CDC (range 37–199) each year. While the 2020–21 and 2021–22 seasons’ disease burden was substantially limited as a result of measures taken by many people to reduce the transmission of COVID-19, such as wearing face masks in public and limiting interactions with other people, influenza activity returned to pre-pandemic levels in 2022–23. For additional information about disease burden from CDC, see www.cdc.gov/flu/about/burden/index.html.

Last reviewed: September 10, 2023

While even healthy children and adults get severe influenza or 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: September 10, 2023

The timing and severity of influenza seasons are always unpredictable. Influenza viruses circulated at very low levels while measures to prevent the spread of COVID-19 were widely adopted, including social distancing, mask wearing, and reduction in travel. As the use of these COVID-19 mitigation measures decreased, there was an increase in the circulation of influenza and other respiratory viruses. Current information on influenza virus circulation can be found at www.cdc.gov/flu/weekly/index.htm.

Last reviewed: September 10, 2023

Yes. Both viruses can circulate at the same time, and a person can be infected with both viruses at the same time. Illnesses experienced by people co-infected with influenza and SARS-CoV-2 are more likely to be severe compared with those infected with only SARS-CoV-2 or influenza alone. The extent to which SARS-CoV-2 and influenza viruses will co-circulate during the upcoming 2023–24 fall and winter respiratory virus season is unknown.

Last reviewed: September 10, 2023

Information regarding influenza surveillance is available year-round from CDC at www.cdc.gov/flu/weekly/fluactivitysurv.htm. The full FluView surveillance report is published each Friday afternoon from October through mid-May and an abbreviated FluView report is published Mid-May through September. In addition, periodic updates about influenza are published in MMWR.

State and local health departments should be consulted regarding local availability of influenza vaccine, access to vaccination programs, information about state or local influenza activity, and for reporting influenza outbreaks and receiving advice regarding their control.

Last reviewed: September 10, 2023

Yearly influenza vaccination continues to be recommended for everyone age 6 months and older. All available influenza vaccines in the United States continue to be quadrivalent (containing two influenza A and two influenza B strains). The changes in the CDC’s published Advisory Committee on Immunization Practices (ACIP) recommendations for influenza vaccination in 2023–2024 are summarized below:

  • The 2023–24 vaccines include a new influenza A(H1N1)pdm09 component and influenza B/Victoria lineage virus vaccine antigens
  • ACIP affirmed that everyone age 6 months and older who has an egg allergy should receive influenza vaccine. Any influenza vaccine (egg based or non-egg based) that is otherwise appropriate for the recipient’s age and health status may be used. ACIP updated its recommendation to state that egg allergy alone necessitates no additional safety measures for influenza vaccination beyond those recommended for any recipient of any vaccine, regardless of severity of previous reaction to egg. All vaccines should be administered in settings in which personnel and equipment needed for rapid recognition and treatment of acute hypersensitivity reactions are available.

The current ACIP recommendations for influenza vaccination are available here: www.cdc.gov/mmwr/volumes/72/rr/pdfs/rr7202a1-H.pdf.

Last reviewed: September 10, 2023

ACIP recommends annual vaccination for all people ages 6 months and older who do not have a contraindication to influenza vaccination.

Last reviewed: September 10, 2023

Multiple manufacturers are producing quadrivalent influenza vaccine for the U.S. market for the 2023–24 season. Inactivated influenza vaccines (IIV4) will be produced using egg-based, cell culture-based, and recombinant technologies. Live attenuated nasal spray vaccine will also be available. Not all influenza vaccines are licensed for all age groups.

Immunize.org has a 1-page printable document that summarizes each of the products available for the current influenza vaccination season at www.immunize.org/catg.d/p4072.pdf.

Last reviewed: September 10, 2023

Vaccine viruses differ by the type of vaccine (egg-based or non-egg-based), but they protect against the same strains of circulating viruses.

For the 2023–24 season, U.S. egg-based influenza vaccines (vaccines other than ccIIV4 and RIV4) will contain hemagglutinin (HA) derived from:
• an influenza A/Victoria/4897/2022(H1N1)pdm09-like virus,
• an influenza A/Darwin/9/2021 (H3N2)-like virus,
• an influenza B/Austria/1359417/2021 (Victoria lineage)-like virus, and
• an influenza B/Phuket/3073/2013(Yamagata lineage)-like virus.

For the 2023–24 season, U.S. cell culture–based inactivated (ccIIV4) and recombinant (RIV4) influenza vaccines will contain HA derived from:
• an influenza A/Wisconsin/67/2022(H1N1)pdm09-like virus,
• an influenza A/Darwin/6/2021 (H3N2)-like virus,
• an influenza B/Austria/1359417/2021 (Victoria lineage)-like virus, and
• an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus.

Last reviewed: September 10, 2023

Four egg-based quadrivalent inactivated influenza vaccines (IIV4s) and one cell-based quadrivalent inactivated influenza vaccine (ccIIV4), all given as intramuscular (IM) injections, are available for children age 6 months and older:

  • Afluria Quadrivalent (CSL Seqirus): 0.25 mL/dose for age 6 through 35 months; 0.5 mL/dose for age 3 years and older
  • Fluarix Quadrivalent (GSK): 0.5 mL/dose for age 6 months and older
  • FluLaval Quadrivalent (GSK): 0.5 mL/dose for age 6 months and older
  • Fluzone Quadrivalent (Sanofi): 0.25 mL or 0.5 mL per dose for age 6 through 35 months; 0.5 mL/dose age 3 years and older
  • Flucelvax Quadrivalent (ccIIV4, CSL Seqirus) cell-based (no egg antigen): 0.5 mL/dose (IM) for age 6 months and older

FluMist Quadrivalent (LAIV4, AstraZeneca) egg-based live nasal spray vaccine is 0.2 mL (intranasal, 0.1 mL in each nostril) for healthy, non-pregnant children and teens age 2 years and older.

Last reviewed: September 10, 2023

Four egg-based quadrivalent standard dose IIV vaccines (SD-IIV4s), and one cell-based quadrivalent standard dose inactivated vaccine (ccIIV4), all given as intramuscular (IM) injection may be used in adults age 18 or older:

  • Afluria Quadrivalent (CSL Seqirus): 0.5 mL/dose
  • Fluarix Quadrivalent (GSK): 0.5 mL/dose
  • FluLaval Quadrivalent (GSK): 0.5 mL/dose
  • Fluzone Quadrivalent (Sanofi): 0.5 mL/dose
  • Flucelvax Quadrivalent (ccIIV4, CSL Seqirus) cell-based (no egg antigen): 0.5 mL/dose (IM) for adults age 18 or older

Additional products for adults:

FluMist Quadrivalent (LAIV4, AstraZeneca): egg-based, live nasal spray vaccine: 0.2 mL (given intranasally, 0.1 mL in each nostril) for healthy, non-pregnant adults through age 49 years.

Flublok Quadrivalent (RIV4, Sanofi): recombinant, egg-free vaccine: 0.5 mL/dose (given IM) for adults age 18 or older (one of three preferred product options for adults age 65 and older).

Fluzone High-Dose Quadrivalent (egg-based HD-IIV4, Sanofi): 0.7 mL (given IM), for adults age 65 years and older (one of three preferred product options for adults age 65 and older).

Fluad Quadrivalent (egg-based aIIV4 with MF59 adjuvant, CSL Seqirus): 0.5 mL (given IM), for adults age 65 years and older (one of three preferred product options for adults age 65 and older).

Last reviewed: September 10, 2023

For people age 6 months through 64 years, CDC recommends any available age-appropriate vaccine product.

For adults age 65 years and older, three flu vaccines are preferentially recommended: Fluzone High-Dose Quadrivalent, Flublok Quadrivalent recombinant, and Fluad Quadrivalent adjuvanted flu vaccines. In June 2022, ACIP concluded that these three vaccines are potentially more effective than standard dose, unadjuvanted flu vaccines. However, if none of the three vaccines are available, people age 65 years and older should get any other age-appropriate flu vaccine.

Review the full explanation for the ACIP decision in the 2022 published ACIP recommendations for influenza vaccination: www.cdc.gov/mmwr/volumes/71/rr/pdfs/rr7101a1-H.pdf.

Last reviewed: September 10, 2023

Children age 6 months through 8 years should receive a second dose 4 weeks or more after the first dose 1) if they are receiving influenza vaccine for the first time, 2) if 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) if their vaccination history is unknown. The two previous doses need not have been received during the same season or consecutive seasons.

Children who are 8 years old and are recommended to receive two doses during the current season but who have a 9th birthday 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: September 10, 2023

For most people who need only 1 dose of influenza vaccine, vaccination should ideally be offered in September and October. For people not vaccinated by the end of October, vaccination efforts should continue as long as influenza viruses are circulating and unexpired vaccine is available.

Vaccination in July and August should be avoided for most groups unless there is concern that vaccination later in the season might not be possible. Early vaccination has been associated with waning of vaccine-induced immunity and decreased vaccine effectiveness before the end of the influenza season, particularly among older adults.

Vaccination in July and August may be considered for people in their third trimester of pregnancy, to allow time for protective maternal antibodies to transfer to the fetus, providing protection during early infancy. Children younger than age 9 years who need two doses of vaccine this season should receive their first dose as soon as possible so that they can get their second dose before the end of October. Children who need only one dose can be considered for vaccination in July or August.

Last reviewed: September 10, 2023

CDC and ACIP make no 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: September 10, 2023

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 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: September 10, 2023

CDC’s clinical guidance for the use of COVID-19 vaccines states that any vaccine may be given on the same day or any day before or after COVID-19 vaccination, at a different anatomic site. According to the CDC’s “General Best Practice Guidelines for Immunization”, simultaneously administering all vaccines for which a person is eligible at the time of a visit increases the probability that a person will be fully vaccinated by the appropriate time.

IIV4 and RIV4 can be administered without regard to the timing of other live or inactivated vaccines. Injectable vaccines should be administered in separate anatomic sites when given on the same day.

LAIV4 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 Shingrix [zoster], Heplisav-B [HepB], Arexvy [RSV] and Fluad [aIIV4, influenza]). Because of the limited data on the safety of simultaneous administration of two or more vaccines containing nonaluminum adjuvants and the availability of nonadjuvanted influenza vaccine options, ACIP advises that selection of a nonadjuvanted influenza vaccine may be considered in situations in which influenza vaccine and another vaccine containing a nonaluminum adjuvant are to be administered at the same visit. However, influenza vaccination should not be delayed if a specific vaccine is not available.

Last reviewed: September 10, 2023

While CDC states that it is acceptable to coadminister influenza and RSV vaccines, there are issues that should be considered before deciding to coadminister these vaccines to a specific patient. Data informing simultaneous administration with influenza vaccines is limited and evolving. Data on coadministration of RSV and influenza vaccines showed that antibody titers were somewhat lower with coadministration; however, the clinical significance of this is unknown. In addition, administering RSV vaccine with one or more other vaccines at the same visit might increase local or systemic reactogenicity. Data are available for coadministration of RSV and influenza vaccines, and evidence is mixed regarding increased reactogenicity.

ACIP advises that when deciding whether 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, risk for acquiring vaccine-preventable disease, vaccine reactogenicity profiles, and patient preferences.

Additional considerations for coadministration of influenza and other vaccines are available in the 2023 ACIP RSV vaccine recommendations for older adults, page 798: www.cdc.gov/mmwr/volumes/72/wr/pdfs/mm7229a4-H.pdf.

Healthcare providers should vaccinate any person who failed to get vaccinated in the previous vaccination season and who wants to reduce their risk of getting influenza during their upcoming travel, particularly if they are at high risk for influenza-related complications. This includes people who are traveling to the tropics, traveling with organized tourist groups at any time of year, or traveling to the Southern Hemisphere during April–September.

Last reviewed: September 10, 2023

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

Last reviewed: September 10, 2023

Because more than one type or subtype of influenza virus can circulate in any given influenza season, 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.

Last reviewed: September 10, 2023

Protection from influenza vaccine wanes over time post-vaccination (the speed of waning varying by strain and by recipient age) but generally persists for at least 5–6 months.

Last reviewed: September 10, 2023

There are several reasons why this misconception persists:

  • Fewer than 1% of people who are vaccinated with the injectable vaccine develop flu-like symptoms, such as mild fever and muscle aches, after vaccination. These side effects are not the same as having influenza, but people confuse the symptoms.
  • Protective immunity doesn’t develop until 1–2 weeks after vaccination. Some people who get vaccinated later in the season (December or later) may be infected with influenza virus shortly afterward. These late vaccinees develop influenza because they were exposed to someone with the virus before they became immune. It is not the result of the vaccination.
  • 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 flu vaccine or think they got “the flu” despite being vaccinated. Influenza vaccine only protects against certain influenza viruses, not all viruses.
  • Influenza vaccination is our best protection against influenza disease; however, some people who are vaccinated will still get influenza illness despite vaccination.

While vaccine effectiveness (VE) can vary, recent studies show that influenza vaccination reduces the risk of illness by between 40% and 60% among the overall population 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 reduces the risk of influenza hospitalization, and deaths in children and adults. Influenza vaccination also reduces the risk of 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: September 10, 2023

Giving patients an influenza Vaccine Information Statement (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). Each can be found at www.immunize.org/vis/ in multiple languages. The current influenza vaccine VISs are dated August 6, 2021.

The latest VIS for all vaccines plus translations in multiple languages are located on the Immunize.org website www.immunize.org/vis/.

Last reviewed: September 10, 2023

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: September 10, 2023

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: September 10, 2023

FluMist Quadrivalent (LAIV4; AstraZeneca) is currently approved by FDA only for healthy non-pregnant people age 2 through 49 years.

Last reviewed: September 10, 2023

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

Last reviewed: September 10, 2023

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 patient 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.

Last reviewed: September 10, 2023

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: September 10, 2023

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

Last reviewed: September 10, 2023

With rare exceptions, yes. Like other live vaccines, FluMist should not be administered to immunosuppressed people. ACIP has stated a preference for using inactivated influenza vaccine for all close contacts of severely immunosuppressed individuals (for example, patients with hematopoietic stem cell transplants) 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. Healthcare personnel or other people who have close contact with people with lesser degrees of immunosuppression (for example, people with diabetes, people with asthma taking corticosteroids, or people living with HIV) who are otherwise eligible for FluMist may receive it. No special precautions need to be taken by the vaccinated person.

Last reviewed: September 10, 2023

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

Last reviewed: September 10, 2023

Asthma is a precaution for FluMist 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: September 10, 2023

An antiviral drug active against influenza virus may reduce the effectiveness of FluMist. ACIP has recommended different intervals between the last dose of an antiviral medication and FluMist administration, based upon the half-life of the antiviral medication. The new recommendations are as follows:

  • Oseltamivir or zanamivir: wait at least 48 hours after 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. All inactivated influenza vaccines and recombinant influenza vaccine (Flublok Quadrivalent) may be administered at any time relative to antiviral medication.

Last reviewed: September 10, 2023

A half dose of FluMist (or any other vaccine) is a non-standard dose and should not be counted. If you were unable to give the second half of the vaccine at that same appointment, 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 inactivated influenza vaccine any time after this partial dose.

Last reviewed: September 10, 2023

ACIP recommends annual influenza vaccination for all children age 6 months and older who do not have a contraindication to the vaccine.

Last reviewed: September 10, 2023

There are now five inactivated influenza vaccine options for children younger than age 3 years.

Cell-culture-based Flucelvax Quadrivalent (ccIIV4, CSL Seqirus) is available to children beginning at age 6 months: administer 0.5 mL/dose intramuscularly (IM).

There are four egg-based quadrivalent inactivated influenza vaccines (IIV4s), all given as IM injections, available for children age 6 through 35 months:
•  Afluria Quadrivalent (CSL Seqirus): 0.25 mL/dose
•  Fluarix Quadrivalent (GSK): 0.5 mL/dose
•  FluLaval Quadrivalent (GSK): 0.5 mL/dose
•  Fluzone Quadrivalent (Sanofi): 0.25 mL or 0.5 mL per dose

Last reviewed: September 10, 2023

Children age 6 months through 8 years should receive a second dose 4 weeks or more after the first dose 1) if they are receiving influenza vaccine for the first time, 2) if 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) if their vaccination history is unknown. The two previous doses need not have been received during the same season or consecutive seasons.

Children who are age 8 years and are recommended to receive two doses during the current season but who have a 9th birthday 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: September 10, 2023

Yes. CDC advises that doses of FluMist administered in past seasons can be counted.

Last reviewed: September 10, 2023

They need just one dose of any appropriate influenza vaccine annually.

Last reviewed: September 10, 2023

The two doses may be the same or different products.

Last reviewed: September 10, 2023

The child should always receive the dose appropriate for his or her age at the time of the clinic visit; at age 37 months that would be a 0.5 mL dose of Afluria Quadrivalent.

Last reviewed: September 10, 2023

Yes. Multi-dose vials of inactivated influenza vaccine contain a small amount of thimerosal to prevent bacterial and fungal growth in the vial. Thimerosal-containing vaccines are safe to use in children. No scientific evidence indicates that thimerosal in vaccines causes adverse events unless the patient has a severe allergy to thimerosal. Despite this, a few states have enacted legislation that restricts the use of thimerosal-containing vaccines in children. To find out if your state has such restrictions, check with your state immunization program (see www.immunize.org/coordinators for contact information).

Last reviewed: September 10, 2023

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 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 current year.
Last reviewed: September 10, 2023

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 PCV15 or PCV20 concurrently with an influenza vaccine has not been studied.

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

Last reviewed: April 5, 2024

Yes. It is especially important to vaccinate during pregnancy because of the increased risk for influenza-related complications during pregnancy and the baby’s increased risk of influenza-related illness and hospitalizations during the first 6 months of life.

Influenza vaccination during pregnancy reduces mothers’ risk of influenza illness, preterm labor, and their infants’ risk of influenza and influenza-related hospitalization in the first 6 months of life.

Vaccination can occur in any trimester, including the first. Only inactivated or recombinant influenza vaccines may be given during pregnancy. FluMist, a live vaccine, should not be given during pregnancy.

Last reviewed: September 10, 2023

ACIP has recommended vaccinating during pregnancy with inactivated influenza vaccine since 1997. Studies have shown that pregnant people are at increased risk for complications, hospitalization, and even death from influenza because of the increased physiologic strain of pregnancy on their heart, lungs, and immune system. Vaccination can occur in any trimester, including the first.

Infants younger than 6 months old are at high risk of influenza-related complications, but influenza vaccine is not recommended for them because the immune response to influenza vaccination is limited before 6 months of age. Vaccinating during pregnancy provides maternal antibodies to the fetus which  helps protect infants against influenza during the first 6 months of life until they can get vaccinated at age 6 months. Vaccinating pregnant people protects them, their unborn babies, and their babies after birth.

Last reviewed: September 10, 2023

Pregnant people may receive any inactivated or recombinant influenza vaccine. They should not be given FluMist Quadrivalent because it is a live-virus vaccine.

Last reviewed: September 10, 2023

Yes, unless you live in a state that has enacted legislation restricting use in pregnancy. There is no scientific evidence that thimerosal in vaccines is a cause of adverse events unless the patient has a systemic allergy to thimerosal.

Last reviewed: September 10, 2023

No. The Advisory Committee on Immunization Practices (ACIP) does not recommend more than one dose of influenza vaccine per season, except for certain children being vaccinated for the first time.

Last reviewed: September 10, 2023

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

Last reviewed: September 10, 2023

No. CDC and ACIP express no preference for preservative-free vaccine for infants or any other group of vaccine recipients.

No scientific evidence exists that thimerosal in vaccines is a cause of adverse events unless the patient has a systemic allergy to thimerosal. However, some states have enacted legislation that restricts the use of thimerosal-containing vaccines. Check with your state immunization manager to see if your state is one of them (www.immunize.org/coordinators).

Last reviewed: September 10, 2023

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

Last reviewed: September 10, 2023

Yes. Multiple sclerosis is not a contraindication to any vaccine, including influenza and pneumococcal vaccines.

Last reviewed: September 10, 2023

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. ACIP believes that annual influenza vaccination with inactivated vaccine will benefit many HIV-infected people.

Last reviewed: September 10, 2023

In November 2015, FDA licensed Fluad (aIIV3, CSL Seqirus), a trivalent, MF59-adjuvanted inactivated influenza vaccine, for people age 65 years and older. Fluad is now quadrivalent (aIIV4). 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 Quadrivalent (Sanofi), Fluad is a standard-dose vaccine, containing 15 mcg of hemagglutinin per virus per dose.

Last reviewed: September 10, 2023

Aging decreases the body’s ability to develop a good immune response after getting influenza vaccine, which places older people at greater risk of severe illness from influenza.

After years of review and deliberation, ACIP voted in June 2022 to recommend that all adults age 65 and older should preferentially receive one of the three different vaccine products that evidence suggests are likely to perform better than standard dose, unadjuvanted vaccines: Flublok recombinant quadrivalent influenza vaccine (RIV4, Sanofi), Fluad quadrivalent adjuvanted vaccine (aIIV4, CSL Seqirus), and Fluzone High-Dose quadrivalent vaccine (HD-IIV, Sanofi). However, if none of these three vaccines is available at the time of vaccination, any age-appropriate influenza vaccine may be administered.

For a thorough review of the evidence for this recommendation, see the 2022 published ACIP recommendations for influenza vaccination: www.cdc.gov/mmwr/volumes/71/rr/pdfs/rr7101a1-H.pdf.

Last reviewed: September 10, 2023

No. These vaccines are licensed only for people age 65 years and older and are not recommended for younger people.

Last reviewed: September 10, 2023

Yes, Flublok is licensed and recommended for adults age 18 years and older.

Last reviewed: September 10, 2023

No, and this is not recommended.

Last reviewed: September 10, 2023

People with cancer need to be protected from influenza, and they can and should receive inactivated or recombinant influenza vaccine (but not live nasal spray vaccine [FluMist]) even if they are immunosuppressed. Cancer patients and survivors are at higher risk for complications from influenza, including hospitalization and death. Here is a helpful CDC web page on cancer and influenza for patients: www.cdc.gov/cancer/flu.

Last reviewed: September 10, 2023

Inactivated influenza vaccine or recombinant influenza vaccine should be administered beginning at least 6 months after bone marrow transplant and annually thereafter for the life of the patient. A dose of vaccine can be given as early as 4 months after transplant, but a second dose should be considered in this situation. A second dose is recommended routinely for all children younger than 9 years receiving influenza vaccine for the first time.

Last reviewed: September 10, 2023

We already encourage them to stay home from work when they are sick. Unfortunately, by the time a HCP has symptoms of influenza, they may have already exposed many patients since the virus is shed for 1–2 days before symptoms begin. Further, many studies show that HCP often go to work while they are sick and may be infectious to others. Start planning early to make sure all employees in your work setting receive annual influenza vaccination before the influenza season begins.

Last reviewed: September 10, 2023

Because HCP provide care to patients at high risk for complications of influenza, they should be considered a high-priority group for receiving vaccination. Achieving high rates of vaccination among HCP will protect staff and their patients, and reduce disease burden and healthcare costs. Vaccination rates of HCP are still too low; overall only 80% of HCP reported influenza vaccination during the 2021–22 season.

Influenza vaccination key points for HCP include:

  • All HCP should be educated regarding the benefits of influenza vaccination
  • Influenza vaccine should be administered annually to all eligible HCP
  • A signed declination should be obtained from HCP who decline influenza vaccination
  • Healthcare facilities should monitor HCP influenza vaccination coverage and declination at regular intervals
  • HCP vaccination coverage should be used as one measure of a patient-safety quality program

In 2011, ACIP published “Immunization of Health-Care Personnel,” which includes information about all recommended vaccines (see www.cdc.gov/mmwr/pdf/rr/rr6007.pdf).

Last reviewed: September 10, 2023

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