What is the difference between Flublok and Flublok Quadrivalent?
Key Points
Flublok Quadrivalent is not being manufactured for the 2025-2026 flu season. All vaccines, including Flublok, are now trivalent, meaning they protect against three influenza strains instead of four. Flu vaccines no longer contain four strains because the B/Yamagata lineage viruses have not been detected globally since March 2020, and the risk of infection with this strain is considered low.
All trivalent flu vaccines for the 2025-2026 flu season target an H1N1 A virus, an H3N2 A virus, and one influenza B (Victoria lineage) virus this season.
Flublok, from Sanofi Pasteur, is a recombinant vaccine for use in people 9 years of age and older. It does not require an egg-grown vaccine virus nor the use of chicken eggs in production. Flublok contains pure protein made without influenza virus, antibiotics, eggs, thimerosal, preservatives, gelatin or latex.
Common side effects include injection site reactions (tenderness, pain), headache, fatigue, and muscle and bone pain.
Do not use Flublok if you have ever had a severe allergic reaction (for example, anaphylaxis) to any component of the vaccine.
This is not all the information you need to know about Flublok for safe and effective use and does not take the place of talking to your doctor about your treatment. Review the full patient information and discuss this information and any questions you have with your doctor or other health care provider.
References
- Recombinant Influenza (Flu) Vaccine. Sept. 9, 2024. US Centers for Disease Control and Prevention (CDC). Accessed Oct 23, 2024 at https://www.cdc.gov/flu/vaccine-types/flublok-vaccine.html
- Flublok Quadrivalent (Influenza Vaccine), Sterile Solution for Intramuscular Injection 2020-2021 Formula. [product label]. Accessed Aug 10, 2023
Read next
How and where is a flu shot injection given?
The flu shot is usually given as an intramuscular (IM) needle injection into the upper, outer arm muscle called the deltoid muscle in people 3 years of age and older. The preferred injection site for infants and young children is the front, outer area of the thigh. The CDC recommends that everyone 6 months of age and older receive a flu vaccine every year, typically in Sept. or Oct.
Continue reading
What flu vaccine can I use with an egg allergy?
Egg-free vaccines include Flublok Quadrivalent, for people 18 years and older and Flucelvax Quadrivalent for people 6 months and older. The CDC now states that people with egg-allergy may receive any flu vaccine appropriate for their age and health status. Continue reading
Where can I get the flu vaccine right now?
You can find the flu vaccine most quickly at your local pharmacy, where you can usually walk in without an appointment. To save time, you might prefer to make an appointment. Call your pharmacist to be sure they have the current year's vaccine in stock. Continue reading
See also:
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Drug information
Related support groups
- Flublok (6 questions, 3 members)
- Flublok Quadrivalent (5 questions, 4 members)
- Influenza Prophylaxis (12 questions, 4 members)