High-Dose Influenza Vaccine shows Increased Immune Response among Older Adults

An investigational high-dose influenza vaccine showed increased immune responses among adults 65 years of age and older compared with the standard influenza vaccine. The revelation was made by Sanofi Pasteur, from the vaccines division of Sanofi-Aventis Group at the 48th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC)/Infectious Diseases Society of America (IDSA) 46th annual meeting.

The study results are considered significant by the medical fraternity as mortality rate from influenza is highest among adults 65 years of age and older. Approximately 90 per cent of the 36,000 average annual influenza-associated respiratory and circulatory related deaths occur among adults 65 years of age and older. "Development of an influenza vaccine that will provide an improved immune response in older adults is important because this population has the highest rates of complications from influenza including hospitalization and death," said Ann R. Falsey, MD Associate Professor of Medicine, University of Rochester School of Medicine, Rochester, NY; Infectious Diseases Unit, Rochester General Hospital.

Currently available, inactivated influenza vaccines offer public health benefits in reducing influenza-related morbidity and mortality in older adults. However, as people age, the immune system tends to weaken making them more susceptible to infections and less responsive to vaccination. When older adults are infected with influenza virus, they are less able to mount an immune response to neutralize the attack.

Sanofi Pasteur conducted a randomized double-blind study at 30 centers throughout the United States in which 2,575 people received the high-dose influenza vaccine while 1,262 received the standard influenza vaccine. The standard influenza vaccine contained 15µg of hemagglutinin (HA) of each of three influenza strains, and the high-dose vaccine contained four times as much i.e. 60µg HA per strain. Both vaccines contained two influenza type A strains (H1N1 and H3N2) and one influenza type B strain.

The key finding of the study is that the new high-dose vaccine increased the immune responses to all three influenza strains compared with standard vaccine in the study population. An important additional observation was that the increased immune response was also observed in the potentially more vulnerable subset of study participants who had no measurable circulating protective antibodies before receiving their annual influenza vaccine.