Explaining the Difference Between Fluad and Fluzone High-Dose
Both Fluad and Fluzone High-Dose are excellent enhanced flu vaccines specifically designed for people 65 and older, and they work equally well—the main difference is that Fluad uses a special immune booster called an adjuvant while Fluzone High-Dose uses four times the amount of flu antigen. 12
How They Differ
Fluad (Adjuvanted Vaccine)
- Contains the standard amount of flu antigen (15 mcg of each flu strain)
- Includes MF59 adjuvant—a special oil-in-water emulsion that acts like a "wake-up call" for your immune system, making it respond more vigorously to the vaccine
- The adjuvant helps your body mount a broader and stronger immune response without needing more antigen 23
Fluzone High-Dose
- Contains four times more flu antigen (60 mcg of each flu strain instead of 15 mcg)
- No adjuvant—relies purely on the higher dose of antigen to stimulate a stronger immune response 1
What This Means for Protection
Both vaccines provide similar protection against flu illness, hospitalization, and complications—multiple studies show they are essentially equivalent in effectiveness for people 65 and older 456. The 2024 CDC guidelines consider them equally acceptable options without preferring one over the other 1.
In solid organ transplant recipients (who have weakened immune systems), both vaccines produced significantly better immune responses than standard-dose vaccines, with response rates of 60% for Fluad and 66% for Fluzone High-Dose compared to only 42% for standard vaccines 7.
Side Effects
Both vaccines cause slightly more arm soreness and mild reactions than standard flu shots, but this is expected and means they're working harder to protect you 8.
- Fluad may cause slightly more injection site reactions due to the adjuvant
- Both have excellent safety profiles with no increased risk of serious complications like Guillain-Barré syndrome 8
- Most side effects are mild and temporary (soreness, fatigue, mild muscle aches)
Bottom Line for Patients
Either vaccine is an excellent choice—both are specifically engineered to overcome the weaker immune response that naturally occurs with aging. The choice often comes down to what's available at your pharmacy or clinic. Both are FDA-approved only for people 65 and older because that's the population that benefits most from these enhanced formulations 12.
You cannot go wrong with either option—what matters most is getting one of these enhanced vaccines rather than a standard-dose flu shot, as both provide superior protection for older adults 37.