Adults 65 and older have three flu vaccines that are preferentially recommended over standard-dose shots: Fluzone High-Dose, Flublok (recombinant), and Fluad (adjuvanted). All three are designed to produce a stronger immune response than a regular flu shot, which matters because the immune system weakens with age and responds less robustly to standard vaccines.
The Three Preferred Vaccines
Each of the three recommended options uses a different strategy to boost protection in older adults. They all cover the same flu strains for the season, but they get your immune system’s attention in different ways.
Fluzone High-Dose takes the most straightforward approach: it simply contains more of the active ingredient. A standard flu shot contains 15 micrograms of flu protein per strain. Fluzone High-Dose packs 60 micrograms per strain, for a total of 240 micrograms. That’s four times the standard amount, which triggers a stronger antibody response in older adults whose immune systems might otherwise underreact.
Fluad (adjuvanted) adds a booster ingredient called an adjuvant to a standard amount of flu protein. The adjuvant works by creating a burst of immune activity at the injection site, drawing in waves of immune cells that pick up the vaccine’s contents and carry them to your lymph nodes. This essentially forces your body to pay closer attention to the vaccine than it otherwise would. The approach is particularly useful for older adults because it can activate parts of the immune system that don’t depend on the specific immune cells that decline most with age.
Flublok (recombinant) uses a completely different manufacturing process. Instead of growing flu virus in chicken eggs (as most vaccines do), Flublok produces flu proteins in insect cells. The result is a purified vaccine with 45 micrograms of flu protein per strain, three times the standard dose. Because it’s egg-free, it’s also an option for people with severe egg allergies, though that’s a secondary benefit for most seniors.
How Much Better Do They Work?
The high-dose vaccine has been the most extensively studied of the three in head-to-head comparisons. In a large randomized trial, it reduced confirmed flu cases by 24% more than the standard-dose vaccine in adults 65 and older. It was also associated with lower rates of probable flu and fewer flu-related hospital admissions. The adjuvanted and recombinant vaccines have shown similar advantages in their own studies, which is why all three carry the same preferential recommendation.
That 24% figure represents the additional benefit on top of whatever protection a standard shot already provides. In practical terms, these enhanced vaccines meaningfully reduce the chance of a hospital visit during flu season, which is the outcome that matters most in this age group. Adults over 65 account for a disproportionate share of flu hospitalizations and deaths each year.
Side Effects Compared to Standard Shots
The tradeoff for a stronger immune response is a somewhat higher chance of side effects, though they tend to be mild. In a study comparing high-dose and standard-dose vaccines in adults 65 and older, 30% of high-dose recipients reported a local side effect (mostly arm soreness) compared to 18% of standard-dose recipients. Systemic side effects like muscle aches and fatigue were also more common with the high-dose shot: about 11% versus 6%. Most of these symptoms were mild to moderate and resolved within a day or two.
The adjuvanted vaccine has a similar side effect profile. You can expect the injection site to be sorer than with a regular flu shot, and you’re somewhat more likely to feel tired or achy afterward. None of the three preferred vaccines carry unusual or serious side effect risks beyond what you’d expect from any flu vaccination.
When to Get Vaccinated
September and October are the ideal months, with the goal of being vaccinated by the end of October. This timing is especially important for adults 65 and older because protection can wane over the course of the season. Getting vaccinated too early, in July or August, risks having your immunity fade before flu activity peaks, which often doesn’t happen until January or February. Getting vaccinated late is still better than skipping it entirely, but the sweet spot is that early-fall window.
What If Your Pharmacy Only Has Standard Shots
Not every pharmacy or doctor’s office stocks all three preferred vaccines. If you can’t find any of the three, a standard-dose flu shot is still far better than no flu shot. The preferential recommendation doesn’t mean you should skip vaccination if only a standard option is available. Call ahead to pharmacies or your doctor’s office to ask which senior flu vaccines they carry. Large chain pharmacies typically stock at least one of the three.
Cost and Medicare Coverage
Medicare Part B covers the seasonal flu shot as a preventive service, once per flu season. You pay nothing out of pocket as long as the provider accepts Medicare assignment. This applies to all three of the preferred senior vaccines, not just the standard shot. Most private insurance plans for people 65 and older cover them as well. Cost should not be a factor in choosing between the standard and enhanced options.
Getting Other Vaccines at the Same Visit
If you’re also due for an RSV or COVID-19 vaccine, you can technically receive them during the same visit as your flu shot. However, limited data suggest that getting an RSV vaccine alongside other respiratory vaccines may result in a somewhat lower antibody response, and combining multiple shots in one visit can increase the likelihood of common side effects like soreness, headache, and fatigue. If returning for a separate visit is practical, spacing them out is reasonable. If it’s not, getting everything at once is still considered safe and effective.