title: Like-with-like comparisons?
authors.forename: Sheila M
authors.initials: SM
authors.lastname: Bird
mesh_terms: D000328:Adult; D000368:Aged; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007109:Immunity; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D008875:Middle Aged; D006113:United Kingdom; D055815:Young Adult