title: Influence of pre-existing hemagglutination inhibition titers against historical influenza strains on antibody response to inactivated trivalent influenza vaccine in adults 50-80 years of age.
abstract: BACKGROUND
  Concerns about influenza vaccine effectiveness in older adults and the role of influenza strains encountered earlier in life led to this study.
  
  
  METHODS
  Antibody responses against antigens in the 2011-2012 influenza vaccine at 21 days post vaccination were analyzed in 264 individuals aged 50-80 years. At Days 0 and 21, sera were tested for hemagglutination-inhibition titers against these vaccine strains and at Day 0 against a panel of 15 historical seasonal strains.:
  
  
  RESULTS
  The proportions of participants with seroprotective titers ≥1:40 to the vaccine strains at Days 0 and 21, respectively, were 37% and 66% for A(H1N1) and 28% and 63% for A(H3N2). An increasing number of responses ≥1:40 against historical strains was associated with seroprotective responses after vaccination among participants with a titer<1:40 at Day 0 for A(H1N1) and A(H3N2) vaccine strains (P<0.01). In multivariable regression analyses among those with Day 0 titer<1:40, after controlling for age, sex, race, site and diabetes, Day 21 titers ≥ 1:40 for the vaccine A strains were significantly more likely as the number of seroprotective responses against historical strains increased (A(H1N1) odds ratio [OR] = 1.41, 95% confidence interval [CI] = 1.09-1.82 and A(H3N2) OR = 1.32, 95% CI = 1.07-1.62). The likelihood of seroconversion was significantly higher with an increasing number of responses to historical strains for A(H3N2) only (OR = 1.24, 95% CI = 1.01-1.52). Seroconversion was significantly less likely as Day 0 vaccine strain titers increased.
  
  
  CONCLUSIONS
  Seroprotective titers after influenza vaccination increased as the number of responses to historical strains increased.
authors.affiliation: Center for Vaccine Research; University of Pittsburgh; Pittsburgh, PA USA; Vaccine & Gene Therapy Institute of Florida; Port Saint Lucie, FL USA.
authors.forename: Ted M
authors.initials: TM
authors.lastname: Ross
authors.affiliation: Department of Family Medicine; School of Medicine; University of Pittsburgh; Pittsburgh, PA USA.
authors.forename: Chyongchiou Jeng
authors.initials: CJ
authors.lastname: Lin
authors.affiliation: Department of Family Medicine; School of Medicine; University of Pittsburgh; Pittsburgh, PA USA.
authors.forename: Mary Patricia
authors.initials: MP
authors.lastname: Nowalk
authors.affiliation: Department of Family Medicine; School of Medicine; University of Pittsburgh; Pittsburgh, PA USA.
authors.forename: Hsin-Hui
authors.initials: HH
authors.lastname: Huang
authors.affiliation: Centers for Disease Control and Prevention; Influenza Division/NCIRD; Atlanta, GA USA.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Spencer
authors.affiliation: Centers for Disease Control and Prevention; Influenza Division/NCIRD; Atlanta, GA USA.
authors.forename: David K
authors.initials: DK
authors.lastname: Shay
authors.affiliation: Centers for Disease Control and Prevention; Influenza Division/NCIRD; Atlanta, GA USA.
authors.forename: Suryaprakash
authors.initials: S
authors.lastname: Sambhara
authors.affiliation: Marshfield Clinic Research Foundation; Marshfield, WI USA.
authors.forename: Maria E
authors.initials: ME
authors.lastname: Sundaram
authors.affiliation: Department of Pathobiological Sciences; University of Wisconsin School of Veterinary Medicine; Madison, WI USA; Wisconsin National Primate Research Center; Madison, WI USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Friedrich
authors.affiliation: UPMC St. Margaret's Family Medicine Residency, Pittsburgh, PA USA.
authors.forename: Sandy
authors.initials: S
authors.lastname: Sauereisen
authors.affiliation: Center for Vaccine Research; University of Pittsburgh; Pittsburgh, PA USA; Vaccine & Gene Therapy Institute of Florida; Port Saint Lucie, FL USA.
authors.forename: Chalise E
authors.initials: CE
authors.lastname: Bloom
authors.affiliation: Department of Family Medicine; School of Medicine; University of Pittsburgh; Pittsburgh, PA USA.
authors.forename: Richard K
authors.initials: RK
authors.lastname: Zimmerman
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000914:Antibodies, Viral / Q000276:immunology*; D000917:Antibody Formation / Q000187:drug effects / Q000276:immunology; D005260:Female; D006384:Hemagglutination / Q000187:drug effects / Q000276:immunology*; D006385:Hemagglutination Inhibition Tests / Q000379:methods; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype / Q000187:drug effects / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000276:immunology
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated
keywords: Human influenza; antibodies; immune response; immunogenicity