Factors Associated With Maintenance of Antibody Responses to Influenza Vaccine in Older, Community-Dwelling Adults

In the United States, yearly influenza vaccination begins in August or September. However, influenza season can extend into April of the following year. The duration of protection from annual vaccination in older adults is unknown, and little is known about factors associated with the maintenance of response throughout the influenza season. This study evaluated factors associated with the immune response of older adults to trivalent influenza vaccine and the maintenance of antibody responses for the duration of the influenza season.

Subjects

Subjects were enrolled at two sites, Vanderbilt University Medical Center (Nashville, TN) and Marshfield Clinic Research Foundation (Marshfield, WI), during September and October 2009. Subjects were eligible for recruitment if they were ≥50 years of age and had no contraindication to influenza vaccination. Subject recruitment included advertisements at Vanderbilt University Medical Center and letters of invitation to older adults who had received an influenza vaccine in the year prior at Marshfield Clinic.1 All subjects were vaccinated either by their usual caregiver or by the study staff. Strain components for the 2009-2010 Northern Hemisphere vaccine included A/Brisbane/59/2007-like (H1N1), A/Brisbane/10/2007-like (H3N2), and B/Brisbane/60/2008-like. Participants were given the trivalent seasonal vaccine because the 2009 H1N1 pandemic vaccine was not available.

Data Collection

All subjects donated serum pre-vaccination (S1) during September through October 2009, 21 - 28 days post-vaccination (S2) and post-influenza season, May through July, 2010, approximately 250 days (8 months) post-vaccination (S3). Study procedures, informed consent documents and data collection forms were reviewed and approved by Institutional Review Boards at each of the study sites.