Fluzone High-Dose: What distinguishes it from other flu vaccines?

Fluzone High-Dose is a flu vaccine for people age 65 and older that's given by injection. Like other flu vaccines, Fluzone High-Dose is made up of the three flu strains most likely to cause the flu during the upcoming flu season. A new vaccine called Fluzone High-Dose Quadrivalent that is made up of four flu strains has been approved for people age 65 and older.

The high-dose vaccines, however, contain four times as much flu virus antigen - the part of the vaccine that stimulates the immune system - as regular Fluzone and other standard flu vaccines. This can give older people a higher immune system response against the flu.

Why is it needed?

Some older adults may have weaker immune systems, which can lead them to be less protected after a regular flu vaccine. In response to a regular flu shot, older people produce 50% to 75% fewer antibodies, which protect against the vaccine antigens, than do younger adults.

Studies have found higher antibody levels in older adults who received high-dose flu vaccines than in those who received standard flu vaccines.

In addition, one study found almost 25% fewer cases of influenza in adults age 65 and older who took the high-dose vaccine compared with those who took the standard-dose vaccine.

Are there side effects?

In a large study comparing high-dose and standard-dose flu vaccines, those who received the high-dose vaccine were more likely to develop side effects during the week after getting the vaccine. Side effects included a fever and soreness at the injection site.

More research needed

People age 65 and older have the highest risks of flu complications. Protecting this group from the flu is especially important.

The U.S. Food and Drug Administration accelerated its approval of Fluzone High-Dose on the condition that studies will continue to evaluate the new vaccine's effect on seasonal flu outcomes, such as flu cases or its complications, in older adults.

If Fluzone High-Dose turns out to have better outcomes than the regular flu vaccine over time, the high-dose vaccine may become the vaccine of choice for older adults. For now, it's most important for everyone to get the annual seasonal flu vaccine.