title: An assessment of mumps vaccine effectiveness by dose during an outbreak in Canada.
abstract: BACKGROUND
  This investigation was done to assess vaccine effectiveness of one and two doses of the measles, mumps and rubella (MMR) vaccine during an outbreak of mumps in Ontario. The level of coverage required to reach herd immunity and interrupt community transmission of mumps was also estimated.
  
  
  METHODS
  Information on confirmed cases of mumps was retrieved from Ontario's integrated Public Health Information System. Cases that occurred between Sept. 1, 2009, and June 10, 2010, were included. Selected health units supplied coverage data from the Ontario Immunization Record Information System. Vaccine effectiveness by dose was calculated using the screening method. The basic reproductive number (R(0)) represents the average number of new infections per case in a fully susceptible population, and R(0) values of between 4 and 10 were considered for varying levels of vaccine effectiveness.
  
  
  RESULTS
  A total of 134 confirmed cases of mumps were identified. Information on receipt of MMR vaccine was available for 114 (85.1%) cases, of whom 63 (55.3%) reported having received only one dose of vaccine; 32 (28.1%) reported having received two doses. Vaccine effectiveness of one dose of the MMR vaccine ranged from 49.2% to 81.6%, whereas vaccine effectiveness of two doses ranged from 66.3% to 88.0%. If we assume vaccine effectiveness of 85% for two doses of the vaccine, vaccine coverage of 88.2% and 98.0% would be needed to interrupt community transmission of mumps if the corresponding reproductive values were four and six.
  
  
  CONCLUSIONS
  Our estimates of vaccine effectiveness of one and two doses of mumps-containing vaccine were consistent with the estimates that have been reported in other outbreaks. Outbreaks occurring in Ontario and elsewhere serve as a warning against complacency over vaccination programs.
authors.affiliation: Ontario Agency for Health Protection and Promotion, Toronto, Ontario. shelley.deeks@oahpp.ca
authors.forename: Shelley L
authors.initials: SL
authors.lastname: Deeks
authors.forename: Gillian H
authors.initials: GH
authors.lastname: Lim
authors.forename: Mary Anne
authors.initials: MA
authors.lastname: Simpson
authors.forename: Louise
authors.initials: L
authors.lastname: Gagné
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gubbay
authors.forename: Erik
authors.initials: E
authors.lastname: Kristjanson
authors.forename: Cecilia
authors.initials: C
authors.lastname: Fung
authors.forename: Natasha S
authors.initials: NS
authors.lastname: Crowcroft
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000097:blood; D002648:Child; D004279:DNA, Viral; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007115:Immunization Schedule; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D022542:Measles-Mumps-Rubella Vaccine / Q000008:administration & dosage* / Q000276:immunology; D008875:Middle Aged; D009107:Mumps / Q000453:epidemiology / Q000517:prevention & control*; D009108:Mumps Vaccine / Q000276:immunology; D009109:Mumps virus / Q000276:immunology / Q000302:isolation & purification; D009864:Ontario / Q000453:epidemiology; D016896:Treatment Outcome; D014611:Vaccination; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D004279:DNA, Viral; D007074:Immunoglobulin G; D022542:Measles-Mumps-Rubella Vaccine; D009108:Mumps Vaccine