In 2009, the U.S. Food and Drug Administration approved a high-dose flu vaccine for people 65 and older. The vaccine is given as a single injection in the arm like the traditional flu shot, but it contains four times the antigen dose per flu strain compared to the standard-dose vaccine.
People 65 and older typically have the highest rates of hospitalization and death from the flu. However, the protection provided by the standard flu shot is not as strong as in younger patients. This might be due to the fact that antibody levels are not high enough with that vaccine. Researchers are exploring a variety of ways to boost the immune response in seniors, and increasing antibody levels with a high-dose vaccine is one of them.
A 2014 study in the New England Journal of Medicine found that the high-dose flu vaccine was 24 percent more effective than the standard dose in preventing influenza in people 65 or older. However, the absolute difference in flu infection between the two groups was small (1.4 percent versus 1.9 percent), so the benefit was relatively modest. Two other studies examined the effect of high-dose versus standard-dose vaccine in preventing flu-related hospitalization in seniors. The first found a 22 percent benefit from the high-dose vaccine, while the second study found the benefit might be limited to patients 85 or older.
Minor side effects such as pain at the injection site, fever above 100.4 degrees, and gastrointestinal symptoms may be slightly more common with the high-dose vaccine. But research has not found a difference in major adverse effects caused by high-dose versus standard-dose flu vaccine.
Both the high-dose and standard-dose shots are considered good flu vaccines for seniors. However, the high-dose vaccine appears to have a modest edge in preventing flu and possibly hospitalization. Because of this, a number of doctors in the Sutter Health network recommend the high-dose flu vaccine for seniors. The current high-dose vaccine contains antigens from three strains of flu virus, and has not been compared with the four-strain standard dose.