title: Factors associated with maintenance of antibody responses to influenza vaccine in older, community-dwelling adults.
abstract: BACKGROUND
  Little is known about factors associated with maintenance of hemagglutinin inhibition (HAI) antibodies after influenza vaccination in older adults.
  
  
  METHODS
  Adults ≥50 years of age were vaccinated prior to the 2009-10 influenza season. Serum was drawn pre-vaccination (S1), 21-28 days post-vaccination (S2), and after the influenza season (S3) for HAI assays. Seroconversion was defined as ≥ 4-fold increase S1 to S2 (or if S1 < 10, by an S2 ≥ 40) and seroprotection was defined as S2 ≥ 40. Maintenance of antibody response was measured in participants with an S2 ≥ 40, and defined as an S3 ≥ 40.
  
  
  RESULTS
  We enrolled 510 participants during Fall 2009 at Vanderbilt University Medical Center and Marshfield Clinic Research Foundation. Participants' mean age was 64 years with 62% female and 96% white. Seroconversion and seroprotection rates were lowest for influenza A H1N1 (12% and 26%, respectively), highest for influenza A H3N2 (45% and 82%), and intermediate for influenza B (28% and 72%). Of the participants with an S2 ≥ 40, 36% (46/126), 71% (289/407), and 74% (263/354) maintained an S3 ≥ 40 for H1N1, H3N2, and B influenza vaccine strains, respectively. S1 HAI titer was strongly associated with both post-vaccination seroprotection and maintaining seroprotection at S3 for all three influenza antigens. Age, sex, body mass index, self-reported stress, and vaccination site were not consistently associated with vaccine response or maintenance of response.
  
  
  CONCLUSIONS
  Pre-vaccination antibody titer was the only study variable consistently and positively associated with both serologic response to vaccination and maintenance of response. Antibody responses were lowest for the H1N1 vaccine strain.
  
  
  RESULTS
  gov Identifier: NCT02401893.
authors.affiliation: Vanderbilt University Medical Center, A2200 MCN 1161 21st Ave, Nashville, TN, 37232, USA. Keipp.talbot@vanderbilt.edu.
authors.forename: H Keipp
authors.initials: HK
authors.lastname: Talbot
authors.affiliation: Abbott Nutrition, 3300 Stelzer Avenue, Columbus, OH, 43219, USA. Laura.coleman@abbott.com.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Coleman
authors.affiliation: Vanderbilt University Medical Center, A2200 MCN 1161 21st Ave, Nashville, TN, 37232, USA. Yuwei.zhu@vanderbilt.edu.
authors.forename: Yuwei
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Centers for Disease Control and Prevention, 1600 Clifton Rd MS A32, Atlanta, GA, 30333, USA. vmf5@cdc.gov.
authors.forename: Sarah
authors.initials: S
authors.lastname: Spencer
authors.affiliation: Centers for Disease Control and Prevention, 1600 Clifton Rd MS A32, Atlanta, GA, 30333, USA. isq8@cdc.gov.
authors.forename: Mark
authors.initials: M
authors.lastname: Thompson
authors.affiliation: Centers for Disease Control and Prevention, 1600 Clifton Rd MS A32, Atlanta, GA, 30333, USA. ewn9@cdc.gov.
authors.forename: Po-Yung
authors.initials: PY
authors.lastname: Cheng
authors.affiliation: University of Minnesota, Minneapolis, MN, 55455, USA. maria.e.sundaram@gmail.com.
authors.forename: Maria E
authors.initials: ME
authors.lastname: Sundaram
authors.affiliation: Marshfield Clinic Research Foundation, 1000 N. Oak Avenue, Marshfield, WI, 54449, USA. belongia.edward@mcrf.mfldclin.edu.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Belongia
authors.affiliation: Vanderbilt University Medical Center, A2200 MCN 1161 21st Ave, Nashville, TN, 37232, USA. marie.griffin@vanderbilt.edu.
authors.forename: Marie R
authors.initials: MR
authors.lastname: Griffin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000914:Antibodies, Viral / Q000097:blood; D000917:Antibody Formation / Q000276:immunology; D005260:Female; D006299:Health Services for the Aged; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D057187:Independent Living; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D053122:Influenza A Virus, H3N2 Subtype / Q000276:immunology; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control*; D008297:Male; D014481:United States; D014611:Vaccination
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines