title: Reduced infectivity of cold-adapted influenza A H1N1 viruses in the elderly: correlation with serum and local antibodies.
abstract: OBJECTIVE
  To compare young and elderly adults in terms of their immune responses and rates of infection following intranasal vaccination with a live attenuated influenza virus.
  
  
  METHODS
  Time series, comparing outcomes in young and elderly convenience sample.
  
  
  METHODS
  Retrospective laboratory analysis of serum and nasal wash specimens collected during prior studies in which young or elderly volunteers had been inoculated with cold-adapted influenza A/Kawasaki/86 (H1N1) reassortant virus.
  
  
  METHODS
  Johns Hopkins Center for Immunization Research.
  
  
  METHODS
  Healthy young and elderly adults with pre-vaccination serum hemagglutination inhibition (HAI) antibody titers less than or equal to 1:8.
  
  
  METHODS
  Antibody responses in serum and nasal washes.
  
  
  RESULTS
  The proportion of vaccinees who developed any serum or local antibody response was higher in young compared with elderly subjects (20/20 vs 5/14, P less than 0.0005). Resistance to infection with cold-adapted virus correlated with pre-vaccination levels of serum immunoglobulin G (IgG), serum IgA, and nasal wash IgA antibody to whole virus antigen. Age was highly correlated with a lack of response to vaccine by simple regression, but not when data were adjusted for pre-existing antibody levels.
  
  
  CONCLUSIONS
  Cold-adapted reassortant influenza A H1N1 viruses achieve lower rates of infection in elderly than young adults, primarily due to age-related differences in preexisting levels of immunity which may not be reflected by HAI titer.
authors.affiliation: Gerontology Research Education and Clinical Center, Saint Louis Veterans Administration Medical Center, Missouri.
authors.forename: D C
authors.initials: DC
authors.lastname: Powers
authors.forename: B R
authors.initials: BR
authors.lastname: Murphy
authors.forename: L F
authors.initials: LF
authors.lastname: Fries
authors.forename: W H
authors.initials: WH
authors.lastname: Adler
authors.forename: M L
authors.initials: ML
authors.lastname: Clements
mesh_terms: D000281:Administration, Intranasal; D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000032:analysis* / Q000097:blood; D003080:Cold Temperature; D004797:Enzyme-Linked Immunosorbent Assay; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007109:Immunity; D007070:Immunoglobulin A / Q000032:analysis; D007074:Immunoglobulin G / Q000032:analysis; D053118:Influenza A Virus, H1N1 Subtype; D009980:Influenza A virus / Q000276:immunology* / Q000502:physiology; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D009297:Nasal Mucosa / Q000276:immunology; D012189:Retrospective Studies
chemical_list: D000914:Antibodies, Viral; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007252:Influenza Vaccines