title: Accelerated vaccination schedule provides protective levels of antibody and complete herd immunity to equine influenza.
abstract: BACKGROUND
  During the 2007 Australian equine influenza (EI) outbreak, an accelerated primary course 14 day intervaccination schedule was proposed, but not widely implemented. Expert opinion was divided as to the efficacy of such a schedule given the lack of published data. This study determined the level and duration of humoral immunity following administration of a recombinant canarypox-vectored vaccine (ALVAC-EIV) with a primary intervaccination interval of 14 days and booster at 105 days.
  
  
  OBJECTIVE
  To examine whether protective levels of immunity of adequate duration were achieved following a primary course reduced from a minimum interval of 28 to 14 days. Antibody responses to 2 H3N8 American lineage virus strains (including A/equine/Sydney/6085/2007) were assessed and compared to previous challenge studies using ALVAC-EIV at conventional intervaccination intervals.
  
  
  METHODS
  Fourteen Thoroughbred horses and 2 ponies from a rural racehorse training property in Victoria, Australia, were vaccinated with ALVAC-EIV on Days 0, 14 and 105. Serial blood samples were collected over the next 32 weeks and tested with haemagglutination inhibition and single radial haemolysis (SRH) in full assays to evaluate the serological response.
  
  
  RESULTS
  All horses and ponies responded to the accelerated ALVAC-EIV vaccination schedule. Mean SRH antibodies remained above those consistent with clinical protection for the duration of the study period. All vaccinates demonstrated high SRH antibodies 14 days following V2, thereby achieving 100% herd immunity to homologous viral challenge.
  
  
  CONCLUSIONS
  An accelerated vaccination schedule conferred long-lasting protective antibody levels despite a >50% reduction in the recommended V1-V2 interval.
  
  
  CONCLUSIONS
  High levels of rapidly acquired herd immunity are critical in containing an outbreak of such a highly contagious pathogen as EIV. In a strategic vaccination programme, it is important that horses remain protected for sufficient time to allow control programmes to succeed. An accelerated 14 day primary course intervaccination interval and booster at 105 days achieves both of these objectives.
authors.affiliation: The Centre for Equine Infectious Diseases, Veterinary Pre-Clinical Centre, University of Melbourne, Victoria, Australia.
authors.forename: C M
authors.initials: CM
authors.lastname: El-Hage
authors.forename: C J
authors.initials: CJ
authors.lastname: Savage
authors.forename: J M
authors.initials: JM
authors.lastname: Minke
authors.forename: N P
authors.initials: NP
authors.lastname: Ficorilli
authors.forename: J
authors.initials: J
authors.lastname: Watson
authors.forename: J R
authors.initials: JR
authors.lastname: Gilkerson
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D006734:Horse Diseases / Q000517:prevention & control*; D006736:Horses; D007115:Immunization Schedule; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D009976:Orthomyxoviridae Infections / Q000517:prevention & control / Q000662:veterinary*; D014611:Vaccination
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines