Fluzone High-Dose is an injected flu vaccine formulated for people age 65 years and older. Like other flu vaccines, Fluzone High-Dose is made up of the three flu strains most likely to cause the flu during the upcoming season. The high-dose vaccine, however, contains 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.
Why is it needed?
In response to a regular flu shot, older people produce 50 to 75 percent fewer antibodies, which protect against the vaccine antigens, than do younger adults.
Evidence that a high-dose flu vaccine can compensate for this difference originally comes from studies that found higher post-vaccine 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 percent fewer cases of proven 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 the largest of three clinical studies comparing high-dose and standard-dose flu vaccines, those who received the high-dose vaccine were more likely to develop side effects, such as a fever and soreness at the injection site, during the week after vaccination.
More research needed
The risks of flu complications are highest for people age 65 years and older, so protecting this group is particularly important. The 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 cases of flu and flu complications, in older adults. If, over the next few years, Fluzone High-Dose turns out to be superior to the regular flu vaccine by these measures, the high-dose vaccine may become the vaccine of choice for older adults.