A study by researchers in Rhode Island and Ohio provides new evidence that well-matched flu vaccinations can save the lives of thousands of elderly residents of nursing homes and prevent thousands more hospitalizations.
Clinical trials have been conducted to determine the costs and benefits of the influenza vaccine to different populations. Recommendations from the CDC suggest that most individuals over the age of 6 months receive an annual vaccination. However, there has been comparatively little research about whether the vaccine is effective among the elderly, and if so, under what conditions.
“In general, people need a significant rise in antibody titers after receiving a vaccine in order to be adequately protected from infection,” says Aurora Pop-Vicas, MD, MPH, Assistant Professor of Medicine at Brown University and an infectious disease physician with Memorial Hospital of Rhode Island. “Several studies have suggested that this rise in antibody titers after flu vaccinations may not be very high in the elderly. The implication is that elderly people, especially those who are most frail, may not be able to mount a strong immunogenic response following flu vaccines. So the question becomes, do they derive any benefit at all?”
“A vaccine with higher effectiveness that provides better protection to nursing home residents and the elderly will prevent more illnesses and hospitalizations, but even a vaccine with reduced effectiveness can prevent illness in nursing homes by protecting those vaccinated and possibly reducing disease transmission.”
— Brendan Flannery, PhD, epidemiologist with the CDC
Dr. Pop-Vicas and fellow researchers conducted a retrospective nine-year longitudinal study of more than 1 million long-stay nursing home residents from the 122 U.S. cities under CDC flu surveillance. Their findings were published in the Journal of the American Geriatrics Society.
“We assembled a bigger database than anyone had ever done before,” says Vincent Mor, PhD, Professor in the School of Public Health at Brown University and Health Scientist with Providence VA Medical Center. “Over many years, we were able to take advantage of the fact that some years, the match of the vaccine to the prevailing strain of flu in the environment is better than in others.”
The researchers found that the degree of match between the vaccine strains and the flu strains that circulate in a given flu season is key to the success of vaccinations in the elderly. The study compared flu-related morbidity and mortality among nursing home residents during years with a good vaccine match versus years with a poor vaccine match, and found that clinical outcomes were significantly improved when the flu vaccines were well-matched to the circulating strains. This was especially true for influenza A/H3N2, the flu strain usually associated with the most severe disease. According to the study’s model, a 50-percentage-point increase in the A/H3N2 match rate, from less than 25 percent to greater than 75 percent, was associated with a 2 percent reduction in mortality and a 4.2 percent reduction in pneumonia- and influenza-related hospitalizations among nursing home residents.
“Translated, this would be approximately 2,560 lives saved and greater than 3,200 hospitalizations prevented annually,” Dr. Pop-Vicas says.