When should I administer an influenza vaccine?

While the best time to vaccinate is in September and October, vaccination should continue after as long as flu viruses are circulating.

Is the flu shot recommended for all my patients?

The influenza vaccine is recommended for all patients 6 months and older.

What if my patient does not want a flu vaccine?

Your recommendation can help. It has been shown that patients are more likely to get an influenza vaccine if it is offered to them by their doctor.

How can I communicate that the flu vaccine is safe and effective?

For resources to help support your patients, please visit our Resources section.

What strain of flu does the flu shot cover?

The influenza vaccine contains one A/H1N1-like strain, one A/H3N2-like strain, and one B/Victoria-like strain.

What is the main antigenic component of the influenza vaccine?

The main antigenic component of the influenza vaccine is hemagglutinin (HA).

What are the key contraindications to influenza vaccination?

The main contraindications to influenza vaccination are allergy to the ingredients or previous severe allergic reaction to an influenza vaccine. When a contraindication is present, a vaccine should not be administered.

How does antigen content influence vaccine effectiveness in older populations?

By providing higher doses of antigen, high-dose vaccines have been shown to provide higher protective influenza titers.

Complications from Flu & the Importance of Vaccination

On this page, you will learn:

Vaccinating your patients against influenza can protect against the flu and potentially severe flu-related complications¹
Provider recommendation strongly influences patient decision to get vaccinated²
In 2025-2026, there were at least 32 million flu-related illnesses and at least 380,000 flu-related hospitalizations³
Who is most at risk of influenza complications: people of advanced age, people with certain chronic illnesses, and pregnant women⁴

It’s only the flu. Until it isn’t.

Not only will vaccinating your patients against influenza help to reduce flu illness, but it may also protect against a variety of potentially severe flu-related complications.¹ Make a recommendation and offer a flu shot to your eligible patients for the upcoming flu season.

Talking to your appropriate patients about the flu vaccine is essential in helping to reduce flu illness and, in some cases, even flu-related hospitalizations. According to the CDC, your recommendation is the strongest predictor of an adult getting vaccinated.^1,2

Seasonal flu vaccination can dramatically reduce flu-related complications and hospitalizations

According to CDC estimates for the 2025-2026 flu season, as of the week ending May 9, 2026, there have been³:

At least

32 million

flu-related illnesses

At least

380,000

flu-related hospitalizations

Source: https://www.cdc.gov/fluview/surveillance/2026-week-18.html

CDC=Centers for Disease Control and Prevention.

However, there is room for improvement in vaccine coverage

Flu vaccine coverage by age group in the 2025-2026 flu season⁵
Demographic group	0-17 Years	18-49 Years	50-64 Years	65+ Years
Flu vaccine coverage, %	48%	16%	27%	55%

Which patients have the greatest risk of influenza complications?

Vaccination for influenza is especially important for those patients at higher risk of developing serious influenza-related complications⁴:

People of advanced age

Although flu infection may carry risk for any age group, the risk of serious complications due to the flu is even higher in people aged 65 and older.⁶

Of patients with influenza-related hospitalizations in 2025-2026⁷:

16% were aged 50-64 years
53% were aged ≥65 years

(According to preliminary CDC influenza-associated hospitalization data as of May 9, 2026.)⁷

The importance of protection from the flu is well established for people aged ≥65 years, but flu vaccination is also important for those aged 50 to 64 years. A recent systematic review of relevant studies found that the disease burden of influenza begins to increase well before age 65.⁸

As well as posing the threat of flu-related health issues, flu infection in the 50-64 age group adds to the economic burden of illness through missed work days, lost productivity, and increased healthcare costs.⁸

People with certain chronic illnesses

Patients who experience influenza infection are at increased risk of developing flu-related complications if they also have pre-existing medical conditions. Examples of common pre-existing conditions include but are not limited to the following categories^4,9:

People with chronic lung disease
Cardiovascular disease
Type 2 diabetes mellitus

In addition to the CDC recommendations for yearly vaccinations, the American Heart Association, the American Lung Association, the American Diabetes Association, and the National Foundation for Infectious Diseases all recommend that annual flu vaccination is the best protection from the complications of the flu.⁹

Pregnant women

The CDC recommends that women receive a flu shot while pregnant and while breastfeeding to help protect themselves and their babies from the flu.¹⁰

Recombinant or inactivated flu vaccines are recommended by the CDC, Advisory Committee on Immunization Practices, and American College of Obstetricians and Gynecologists for women who are pregnant or will become pregnant during flu season.^1,11

There are no data to determine the effects of Flublok^® (influenza vaccine) on breastfed infants or on milk production/excretion.

Healthcare providers are encouraged to enroll women who receive Flublok during pregnancy in Sanofi’s vaccination pregnancy registry by calling 1-800-822-2463.

People of advanced age

People with certain chronic illnesses

Pregnant people

Frequently asked questions

According to the CDC, vaccines against the flu, COVID-19, and respiratory syncytial virus (RSV) may all be administered at the same visit if the patient is eligible and the timing for each vaccine is right, which may be more convenient for the patient. No clinical trial data are available yet for all 3 vaccines administered at the same time. For additional information, visit the CDC website.¹³

Per the CDC, people with egg allergy may receive an egg-based or non-egg-based vaccine that is otherwise appropriate for their age and health status. All vaccines should be administered in settings in which staff and equipment are available to quickly recognize and treat allergic reactions as needed.¹⁴ Fluzone^® (Influenza Vaccine), Flublok, and Fluzone^® High-Dose (Influenza Vaccine) should not be given to anyone who has had a severe allergic reaction (anaphylaxis) to any component of the vaccine (including egg protein for Fluzone and Fluzone High-Dose). In addition, Fluzone and Fluzone High-Dose should not be given to anyone who has had a severe allergic reaction after a previous dose of any influenza vaccine.^15-17

Influenza vaccines can help protect your appropriate patients, including some of the most at-risk, from flu-related complications.

Make a recommendation for vaccination this flu season.

For patients 9+ years

About Flublok

Flublok has been shown to help protect patients aged 18+ against flu and its complications^16,22

Learn about Flublok

For patients 65+ years

About Fluzone High-Dose

The only high-dose flu vaccine shown to protect against flu and its complications^17,23,24

Learn about Fluzone High-Dose

For patients 6+ months

About Fluzone

An influenza vaccine for people 6+ months¹⁵

Learn about Fluzone

Important Safety Information

Do not administer Fluzone, Flublok, or Fluzone High-Dose to anyone with a history of a severe allergic reaction (e.g., anaphylaxis) to any component of the vaccine (including egg protein for Fluzone and Fluzone High-Dose). Fluzone and Fluzone High-Dose should not be administered to anyone who has had a severe allergic reaction after previous dose of any influenza vaccine.

Appropriate medical treatment must be immediately available to manage potential anaphylactic reactions following administration of the vaccine.

If Guillain-Barré syndrome has occurred within 6 weeks following previous influenza vaccination, the decision to give Fluzone, Flublok, or Fluzone High-Dose should be based on careful consideration of the potential benefits and risks.

Syncope (fainting) has been reported following vaccination with Fluzone, Flublok and Fluzone High-Dose. Procedures should be in place to avoid injury from fainting.

In two separate postmarketing observational studies, an increased risk of febrile seizures was observed during the first day following vaccination with standard dose trivalent (2024-2025) and quadrivalent (2023-2024) influenza vaccines in children 6 months through 4 years of age.

If Fluzone, Flublok, or Fluzone High-Dose are administered to immunocompromised persons, including those receiving immunosuppressive therapy, the expected immune response may not be attained.

Vaccination with Fluzone, Flublok, or Fluzone High-Dose may not protect all recipients.

For Fluzone, in children 6 months through 8 years of age, the most common injection-site adverse reactions were pain or tenderness and redness; the most common solicited systemic adverse reactions were irritability, drowsiness (6 months through 35 months), and myalgia (3 years through 8 years). In adults 18 through 64 years of age, the most common injection-site adverse reaction was pain; the most common solicited systemic adverse reactions were headache and myalgia. In adults over 65 years of age, the most common injection-site adverse reaction was pain; the most common solicited systemic adverse reactions were headache, myalgia, and malaise.

For Flublok, in children 9 through 17 years of age who received Flublok Quadrivalent, the most common solicited injection-site adverse reaction was pain; the most common solicited systemic adverse reactions were myalgia, headache, and malaise. In adults 18 through 64 years of age who received Flublok, the most common injection site adverse reaction was pain; the most common solicited systemic adverse reactions were headache, fatigue, and myalgia. In adults 65 years of age and older who received Flublok, the most common injection-site adverse reaction was pain; the most common solicited systemic adverse reactions were fatigue and headache.

For Fluzone High-Dose, in adults 65 years of age and older, the most common injection-site reaction was pain; the most common solicited systemic adverse reactions were myalgia, malaise, and headache.

For Fluzone, Flublok, and Fluzone High-Dose, other adverse reactions may occur.

Indications

Fluzone, Flublok, and Fluzone High-Dose are vaccines indicated for active immunization for the prevention of disease caused by influenza A virus subtypes and type B virus contained in (or in the case of Flublok, represented by antigens contained in) the vaccine. Fluzone is approved for use in persons 6 months of age and older. Flublok is approved for use in individuals 9 years of age and older. Fluzone High-Dose is approved for use in persons 65 years of age and older.

Before administration, please see the full Prescribing Information for Fluzone, Flublok, or Fluzone High-Dose. Also, please see complete Patient Information for Fluzone or Fluzone High-Dose.

Click here to learn more about Sanofi's commitment to fighting counterfeit drugs.

Important Safety Information

Indications

References: 1. Grohskopf LA, Blanton LH, Ferdinands JM, Reed C, Dugan VG, Daskalakis DC. Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2025–26 Influenza Season. MMWR Morbidity and Mortality Weekly Report2025;74(32):500-507. doi:10.15585/mmwr.mm7432a2 2. Centers for Disease Control and Prevention. Strategies for increasing adult vaccination rates. Accessed August 20, 2026. https://www.cdc.gov/vaccines-adults/hcp/vaccination-guidelines/index.html 3. Centers for Disease Control and Prevention. Weekly US influenza surveillance report: key updates for week 18, ending May 9, 2026. Published May 15, 2026. Accessed May 21, 2026. https://www.cdc.gov/fluview/surveillance/2026-week-18.html 4. Centers for Disease Control and Prevention. People at increased risk for flu complications. Accessed October 9, 2024. https://www.cdc.gov/flu/highrisk/index.htm 5. Sanofi. Data on file. 6. Centers for Disease Control and Prevention. Flu symptoms and complications. Accessed July 29, 2025. https://www.cdc.gov/flu/signs-symptoms 7. Centers for Disease Control and Prevention. Laboratory confirmed influenza hospitalizations. Preliminary data week of May 9, 2026. Accessed May 21, 2026. https://gis.cdc.gov/grasp/FluView/FluHospRates.html 8. Marchi S, Fallani E, Salvatore M, et al. The burden of influenza and the role of influenza vaccination in adults aged 50-64 years: a summary of available evidence. Hum Vaccin Immunother. 2023;19(2):2257048. doi:10.1080/21645515.2023.2257048 9. American Heart Association. Complications from flu largely preventable with annual flu vaccine. Accessed July 1, 2025. https://newsroom.heart.org/news/complications-from-flu-largely-preventable-with-annual-flu-vaccine 10. Centers for Disease Control and Prevention. Flu vaccine safety and pregnancy. Accessed June 27, 2025. https://www.cdc.gov/flu/vaccine-safety/vaccine-pregnant.html 11. American College of Obstetricians & Gynocologists. The flu vaccine and pregnancy. Accessed August 26, 2026. https://www.acog.org/womens-health/faqs/the-flu-vaccine-and-pregnancy 12. Centers for Disease Control and Prevention. ACIP recommendations summary. Accessed August 21, 2026. https://www.cdc.gov/flu/hcp/vax-summary/acip-recommendations.html 13. Centers for Disease Control and Prevention. National Center for Immunization and Respiratory Diseases. What to know about getting flu, COVID-19, and RSV vaccines at the same time. Accessed July 1, 2025. https://www.cdc.gov/ncird/whats-new/getting-vaccines-at-same-time.html 14. Centers for Disease Control and Prevention. Flu vaccine and people with egg allergies. Accessed June 30, 2025. https://www.cdc.gov/flu/prevent/egg-allergies.htm 15. Fluzone. Prescribing Information. Sanofi Pasteur Inc. 16. Flublok. Prescribing Information. Protein Sciences Corporation. 17. Fluzone High-Dose. Prescribing Information. Sanofi Pasteur Inc. 18. American Academy of Family Physicians. Clinical guidance: prevention and control of seasonal influenza with vaccines: 2025-2026 recommendations. Published November 2025. Accessed March 19, 2026. https://www.aafp.org/assets/image/upload/v1769717950/cqbx0cupeaomtr8inri6.pdf 19. American Academy of Pediatrics. Recommendations for prevention and control of influenza in children, 2025–2026: policy statement. Pediatrics. 2025;156(6):e2025073620. doi:10.1542/peds.2025-073620 20. Centers for Disease Control and Prevention. Selecting viruses for the seasonal influenza vaccine. Published June 17, 2026. Accessed July 28, 2026. https://www.cdc.gov/flu/vaccine-process/vaccine-selection.html 21. Falsey AR, et al. J Infect Dis. 2009;200(2):172-180. doi:10.1086/599790 22. Dunkle LM, Izikson R, Patriarca P, et al; PSC12 Study Team. N Engl J Med. 2017;376(25):2427-2436. doi:10.1056/NEJMoa1607762 23. DiazGranados CA, et al. N Engl J Med. 2014;371(7):635-645. doi:10.1056/NEJMoa1315727 24. Lee JKH, et al. Vaccine X. 2023;14:100327. doi:10.1016/j.jvacx.2023.100327

Talk to your patients about the flu

It’s only the flu. Until it isn’t.

Seasonal flu vaccination can dramatically reduce flu-related complications and hospitalizations

According to CDC estimates for the 2025-2026 flu season, as of the week ending May 9, 2026, there have been3:

32 million

380,000

However, there is room for improvement in vaccine coverage