title: Measles Outbreak Among Previously Immunized Healthcare Workers, the Netherlands, 2014.
abstract: BACKGROUND
  We investigated a measles outbreak among healthcare workers (HCWs) by assessing laboratory characteristics, measles vaccine effectiveness, and serological correlates for protection.
  
  
  METHODS
  Cases were laboratory-confirmed measles in HCWs from hospital X during weeks 12-20 of 2014. We assessed cases' severity and infectiousness by using a questionnaire. We tested cases' sera for measles immunoglobulin M, immunoglobulin G, avidity, and plaque reduction neutralization (PRN). Throat swabs and oral fluid samples were tested by quantitative polymerase chain reaction. We calculated attack rates (ARs) by vaccination status and estimated measles vaccine effectiveness as 1 - [ARvaccinated/ARunvaccinated].
  
  
  RESULTS
  Eight HCWs were notified as measles cases; 6 were vaccinated with measles vaccine twice, 1 was vaccinated once, and 1 was unvaccinated. All 6 twice-vaccinated cases had high avidity and PRN titers. None reported severe measles or onward transmission. Two of 4 investigated twice-vaccinated cases had pre-illness PRN titers of >120 mIU/mL. Among 106 potentially exposed HCWs, the estimated effectiveness of 2 doses of measles vaccine was 52% (95% confidence interval [CI], -207%-93%).
  
  
  CONCLUSIONS
  Measles occurred in 6 twice-vaccinated HCWs, despite 2 having adequate pre-exposure neutralizing antibodies. None of the twice-vaccinated cases had severe measles, and none had onward transmission, consistent with laboratory findings suggesting a secondary immune response. Improving 2-dose MMR coverage among HCWs would have likely reduced the size of this outbreak.
authors.affiliation: Center for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven.
authors.forename: Susan J M
authors.initials: SJ
authors.lastname: Hahné
authors.affiliation: Center for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven.|European Programme for Intervention Epidemiology Training, European Centre for Disease Prevention and Control, Stockholm, Sweden.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Nic Lochlainn
authors.affiliation: Haga Hospital.
authors.forename: Nathalie D
authors.initials: ND
authors.lastname: van Burgel
authors.affiliation: Center for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Kerkhof
authors.affiliation: Center for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven.|European Programme for Intervention Epidemiology Training, European Centre for Disease Prevention and Control, Stockholm, Sweden.
authors.forename: Jussi
authors.initials: J
authors.lastname: Sane
authors.affiliation: Municipal Health Service Haaglanden, the Hague, The Netherlands.
authors.forename: Kioe Bing
authors.initials: KB
authors.lastname: Yap
authors.affiliation: Center for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven.
authors.forename: Rob S
authors.initials: RS
authors.lastname: van Binnendijk
mesh_terms: D000328:Adult; D057134:Antibodies, Neutralizing / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood; D000915:Antibody Affinity; D004196:Disease Outbreaks; D005260:Female; D006282:Health Personnel; D006761:Hospitals; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D008297:Male; D008457:Measles / Q000453:epidemiology* / Q000473:pathology; D022542:Measles-Mumps-Rubella Vaccine / Q000008:administration & dosage / Q000276:immunology; D009426:Netherlands / Q000453:epidemiology; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D022542:Measles-Mumps-Rubella Vaccine
keywords: measles; outbreak; vaccination; vaccine failure; waning immunity