The flu is nothing to sneeze at, particularly if you’re 65 or older. People in that age group account for approximately 90 percent of the deaths from the seasonal flu each year, according to the Centers for Disease Control and Prevention (CDC). That’s why the agency recommends that older adults .    

But not everyone gets equal protection from the shot. Vaccines work by giving the immune system a sneak preview of incoming germs, so infection-fighting cells can respond more quickly when the real threat strikes. As we age, immune cells lose their ability to “remember” vaccines, making them less effective. In fact, studies show that the influenza vaccine is only 30 to 50 percent as effective in the elderly as it is in younger adults. [Read "New High Dose Vaccine Approved," 1/6/09.]

As a result, the CDC now recommends people 65 and older get a special vaccine. Fluzone High-Dose was approved by the Food and Drug Administration in 2009. This formula contains four times the antigen dose given in a standard flu vaccine. Antigens are the active ingredients in vaccines that prime the immune system to respond when threatened.

“Elderly persons are at increased risk for complications of influenza. This is the first influenza vaccine that uses a higher antigen dose,” says FDA spokeswoman Shelly Burgess.

Previous research from the Center for Vaccine Development at the University of Maryland in Baltimore had demonstrated that elderly study participants needed this four-fold stronger dose in order to stimulate the same immune response as adults younger than 40.

Fluzone High-Dose is a single injection given in the upper arm, and has been available since the 2011-2012 flu season. It contains the same ingredients as the standard vaccine, and because it is inactivated, it is considered safe for people with weakened immune systems.

In clinical trials, a total of 3,876 individuals ages 65 and older received either Fluzone High-Dose or Fluzone (one of the available standard-dose vaccines) at multiple centers, and the FDA says the results were promising.

“The data demonstrated that vaccination with Fluzone High-Dose resulted in higher immune responses in older individuals,” Burgess says.

In the study, roughly twice the number of the participants on Fluzone High-Dose as those taking the standard vaccine, 48.6 percent compared to 23.1 percent, had detectable antibodies to an influenza A strain.

The FDA says because of the higher dose, there was an increase in side effects, but they were not serious. Common complaints during clinical studies included pain, redness and swelling at the injection site, headache, muscle aches, fever and malaise. People with hypersensitivity to egg proteins or people who have had life-threatening reactions to previous influenza vaccines should not be vaccinated with Fluzone High-Dose.