title: Influenza vaccination responses: Evaluating impact of repeat vaccination among health care workers.
abstract: To compare the antibody response to influenza between health care workers (HCWs) who have received multiple vaccinations (high vaccination group) and those who have received fewer vaccinations (low vaccination group).
  
  
  
  Prospective serosurvey.
  
  
  
  Tertiary referral hospital.
  
  
  
  Healthcare workers.
  
  
  
  Healthcare workers were vaccinated with the 2015 southern hemisphere trivalent influenza vaccine. Influenza antibody titres were measured pre-vaccination, 21-28days post-vaccination and 6months post-vaccination. Antibody titres were measured using the haemagglutination inhibition assay. Levels of seropositivity and estimated geometric mean titres were calculated.
  
  
  
  Of the 202 HCWs enrolled, 182 completed the study (143 high vaccination and 39 low vaccination). Both vaccination groups demonstrated increases in post-vaccination geometric mean titres, with greater gains in the low vaccination group. Seropositivity remained high in both high and low vaccination groups post-vaccination. The highest fold rise was observed among HCWs in the low vaccination group against the H3N2 component of the vaccine.
  
  
  
  Both high and low vaccination groups in our study demonstrated protective antibody titres post-vaccination. The findings from the current study are suggestive of decreased serological response among highly vaccinated HCWs. More studies with larger sample sizes and a greater number of people in the vaccine-naïve and once-vaccinated groups are required to confirm or refute these findings before making any policy changes.
authors.affiliation: WHO Collaborating Centre for Reference and Research on Influenza, Peter Doherty Institute for Infection and Immunity, 792 Elizabeth St, Melbourne, VIC 3000, Australia; Department of Infectious Diseases/Infection Prevention, Peter MacCallum Cancer Centre, 305 Grattan Street, Melbourne, VIC 3000, Australia.
authors.forename: Vivian K Y
authors.initials: VKY
authors.lastname: Leung
authors.affiliation: WHO Collaborating Centre for Reference and Research on Influenza, Peter Doherty Institute for Infection and Immunity, 792 Elizabeth St, Melbourne, VIC 3000, Australia.
authors.forename: Louise A
authors.initials: LA
authors.lastname: Carolan
authors.affiliation: Department of Infectious Diseases/Infection Prevention, Peter MacCallum Cancer Centre, 305 Grattan Street, Melbourne, VIC 3000, Australia.
authors.forename: Leon J
authors.initials: LJ
authors.lastname: Worth
authors.affiliation: Department of Infectious Diseases/Infection Prevention, Peter MacCallum Cancer Centre, 305 Grattan Street, Melbourne, VIC 3000, Australia.
authors.forename: Susan A
authors.initials: SA
authors.lastname: Harper
authors.affiliation: WHO Collaborating Centre for Reference and Research on Influenza, Peter Doherty Institute for Infection and Immunity, 792 Elizabeth St, Melbourne, VIC 3000, Australia.
authors.forename: Heidi
authors.initials: H
authors.lastname: Peck
authors.affiliation: WHO Collaborating Centre for Reference and Research on Influenza, Peter Doherty Institute for Infection and Immunity, 792 Elizabeth St, Melbourne, VIC 3000, Australia.
authors.forename: Danielle
authors.initials: D
authors.lastname: Tilmanis
authors.affiliation: WHO Collaborating Centre for Reference and Research on Influenza, Peter Doherty Institute for Infection and Immunity, 792 Elizabeth St, Melbourne, VIC 3000, Australia.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Laurie
authors.affiliation: Department of Infectious Diseases/Infection Prevention, Peter MacCallum Cancer Centre, 305 Grattan Street, Melbourne, VIC 3000, Australia.
authors.forename: Monica A
authors.initials: MA
authors.lastname: Slavin
authors.affiliation: WHO Collaborating Centre for Reference and Research on Influenza, Peter Doherty Institute for Infection and Immunity, 792 Elizabeth St, Melbourne, VIC 3000, Australia; Fielding School of Public Health, University of California, Los Angeles, USA; School of Population and Global Health, University of Melbourne, Melbourne, Australia. Electronic address: sheena.sullivan@influenzacentre.org.
authors.forename: Sheena G
authors.initials: SG
authors.lastname: Sullivan
mesh_terms: D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000097:blood*; D000917:Antibody Formation; D005260:Female; D006282:Health Personnel; D006801:Humans; D007117:Immunization, Secondary; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D062606:Tertiary Care Centers; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines
keywords: Antibody; Focus reduction assay; Healthcare worker; Hemagglutination inhibition assay; Immunogenicity; Influenza vaccine