The CDC strongly recommends that adults over age 65 be vaccinated with seasonal flu vaccine every year. This can either be the usual seasonal flu shot or the new high-dose
flu shot, called Fluzone High-Dose. This vaccine was designed specifically for those over age 65, and it contains four times more flu antigen than the usual flu shot.
This high-dose flu shot was approved by the FDA in December 2009, after clinical trials showed that the higher-dose vaccine is more likely to generate high antibody levels in older people. (Since the immune system often gets weaker as people age, some older people don't create high levels of antibodies after getting vaccinated for the flu.)
However, nobody yet knows whether vaccination with this high-dose flu vaccine will actually reduce illnesses and deaths due to influenza in older adults, compared to vaccination with the usual dose of vaccine.
For this reason, the CDC currently doesn't say whether older adults should or shouldn't get the special high-dose vaccine. Instead, the CDC says that either dose can be used.
In terms of safety, so far the CDC reports that the higher-dose vaccine does seem slightly more likely to cause the minor side effects known to be linked to flu vaccine (such as arm soreness or mild fever). However, most people who received the high-dose vaccine had no or minimal side effects.