title: Estimated protective effectiveness of intramuscular immune serum globulin post-exposure prophylaxis during a measles outbreak in British Columbia, Canada, 2014.
abstract: Intramuscular Immune Serum Globulin (IM ISG) is recommended as post-measles exposure prophylaxis (PEP) when administered within 6days of initial exposure, with variable effectiveness in preventing measles disease. Effectiveness of IM ISG PEP in preventing clinical measles was assessed during a 2014 measles outbreak among a religious-affiliated community in British Columbia, Canada.
  
  
  
  Fifty-five self-reporting measles susceptible contacts were offered exclusively IM ISG PEP within an eligibility period best surmised to be within 6days of initial measles case exposure. Clinical outcome of IM ISG PEP recipients was determined by selective active surveillance and case self-reporting. IM ISG PEP failure was defined as onset of a measles-like rash 8-21days post-IM ISG PEP. Post-IM ISG PEP measles IgG antibody level was tested in 8 recipients. Factors associated with measles disease were analyzed.
  
  
  
  Seventeen of 55 IM ISG PEP recipients developed clinically consistent measles in the following 8-21days, corresponding to an estimated crude protective effectiveness of 69%. In school aged children 5-18years, among whom potential exposure intensity and immune status confounders were considered less likely, estimated IM ISG PEP protective effectiveness was 50%. Age <25years was significantly associated with breakthrough clinical measles in bivariate analysis (p=0.0217). Among 8 tested contacts of 17 considered IM ISG PEP failures, post-IM ISG PEP measles IgG antibody levels (mean 16.3days (range 16-17days) post-PEP) were all <150mIU/ml.
  
  
  
  The estimated crude IM ISG PEP protective effectiveness against measles disease within 8-21days post-ISG administration was 69%. Accuracy of this estimated protective effectiveness is vulnerable to assumptions and uncertainties in ascertaining exposure details and pre-exposure immune status. Increasing the Canadian recommended measles IM ISG PEP dose from 0.25 to 0.5ml/kg (up to 15ml maximum volume) may increase protective effectiveness.
authors.affiliation: Fraser Health Authority, Office of the Chief Medical Health Officer, #400-13450 102 Ave, Surrey, British Columbia V3T 0H1, Canada. Electronic address: mark.bigham@fraserhealth.ca.
authors.forename: Mark
authors.initials: M
authors.lastname: Bigham
authors.affiliation: Fraser Health Authority, Office of the Chief Medical Health Officer, #400-13450 102 Ave, Surrey, British Columbia V3T 0H1, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Murti
authors.affiliation: Fraser Health Authority, Office of the Chief Medical Health Officer, #400-13450 102 Ave, Surrey, British Columbia V3T 0H1, Canada.
authors.forename: Christina
authors.initials: C
authors.lastname: Fung
authors.affiliation: Fraser Health Authority, Office of the Chief Medical Health Officer, #400-13450 102 Ave, Surrey, British Columbia V3T 0H1, Canada.
authors.forename: Felicity
authors.initials: F
authors.lastname: Hemming
authors.affiliation: Fraser Health Authority, Office of the Chief Medical Health Officer, #400-13450 102 Ave, Surrey, British Columbia V3T 0H1, Canada.
authors.forename: Susan
authors.initials: S
authors.lastname: Loadman
authors.affiliation: Fraser Health Authority, Office of the Chief Medical Health Officer, #400-13450 102 Ave, Surrey, British Columbia V3T 0H1, Canada.
authors.forename: Robert
authors.initials: R
authors.lastname: Stam
authors.affiliation: Fraser Health Authority, Office of the Chief Medical Health Officer, #400-13450 102 Ave, Surrey, British Columbia V3T 0H1, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Van Buynder
authors.affiliation: Fraser Health Authority, Office of the Chief Medical Health Officer, #400-13450 102 Ave, Surrey, British Columbia V3T 0H1, Canada.
authors.forename: Marcus
authors.initials: M
authors.lastname: Lem
mesh_terms: D000293:Adolescent; D000328:Adult; D001955:British Columbia / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007136:Immunoglobulins / Q000008:administration & dosage*; D007223:Infant; D007273:Injections, Intramuscular; D008297:Male; D008457:Measles / Q000453:epidemiology* / Q000517:prevention & control*; D056990:Post-Exposure Prophylaxis / Q000379:methods*; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D007136:Immunoglobulins
keywords: Effectiveness; Immune serum globulin; Measles; Post-exposure prophylaxis