PITTSBURGH - Giving frail, older residents of long-term care facilities a high-dose flu vaccine produces a significantly better immune response than a regular flu shot, a University of Pittsburgh School of Medicine study has found.

Published in the Journal of Infectious Diseases and funded by Fluzone High-Dose vaccine-maker Sanofi Pasteur, the study marks the first time the efficacy of the high-dose vaccine already on the market was evaluated for long-term care residents.

That population, the most vulnerable to flu-related death, has historically shown only moderate benefits from the standard flu vaccine. Among the elderly population, clinical efficacy of the standard vaccine is reduced by 17 to 60 percent.

The U.S. Food and Drug Administration licensed Fluzone High-Dose in December 2009 as a vaccine specifically designed for people 65 years of age and older. It contains four times the antigen of regular shots that prompts the immune system to make antibodies against the flu.

But health-care providers wondered whether it would work for the frail and elderly and whether it was worth the cost - twice that of a regular flu vaccine but likewise covered by Medicare - even if it had some benefit, said David A. Nace, the study's lead author.

The findings answer those questions in the affirmative, said Nace, director of long-term care and flu programs in Pitt's Division of Geriatric Medicine and chief medical officer for UPMC Senior Communities.

"What this [study] shows is that for this very vulnerable population it makes complete sense that if you're going to do anything, go all out and go high dose. If it were my parents, I'd want them to have this [high-dose vaccine]."

The Pitt study involved 187 people with an average age of 86.7 years living in 15 community-based, long-term care sites in Western Pennsylvania. It found that those who received the high-dose vaccine had a higher immune response than the standard vaccine for all the flu strains in the 2011-12 and 2012-13 flu seasons except for one strain. There were no serious adverse reactions to the vaccine, Nace noted.