title: Local public health response to vaccine-associated measles: case report.
abstract: BACKGROUND
  The most appropriate public health approach to vaccine-associated measles in immunocompromised patients is unknown, mainly because these cases are rare and transmission of vaccine-associated measles has not been previously documented. In this case report, we describe Peel Public Health's response to a vaccine-associated measles case in an immunocompromised child in Ontario, Canada.
  
  
  METHODS
  A five-year-old Canadian-born boy with a history of a hematopoetic stem cell transplant three years previously received live attenuated measles, mumps, and rubella (MMR) vaccine. Over the subsequent 7 to 14 days, he developed an illness clinically consistent with measles. There was no travel history or other measles exposure. Serology and polymerase chain reaction (PCR) testing confirmed acute measles infection. Following discussion with pediatric infectious diseases specialists, but prior to the availability of virus sequencing, it was felt that this case was most likely due to vaccine strain. Although no microbiologically confirmed secondary cases of vaccine-associated measles have been previously described, we sent notification letters to advise all contacts of measles symptoms since the likelihood of transmission from an immunocompromised patient was low, but theoretically possible. We decided to stratify contacts into immune competent and compromised and to deal with the latter group conservatively by excluding them as if they were exposed to wild-type measles because the risk of transmission of disease in this population, while presumably very low, is unknown. However, no contacts self-identified as immunocompromised and there were no secondary cases. Subsequent genotyping confirmed that this case was caused by vaccine strain measles virus.
  
  
  CONCLUSIONS
  The public health approach to contact tracing and exclusions for vaccine-associated measles in immunocompromised patients is unclear. The rarity of secondary cases provides further evidence that the risk to the general public is likely extremely low. Although the risk appears negligible, exclusion and administration of immune globulin may be considered for susceptible, immunocompromised contacts of cases of vaccine-associated measles in immunocompromised patients.
authors.affiliation: Peel Public Health, 7120 Hurontario St, RPO Streetsville, PO Box 667, Mississauga, ON L5M 2C2, Canada. monica.hau@peelregion.ca
authors.forename: Monica
authors.initials: M
authors.lastname: Hau
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Schwartz
authors.forename: Crystal
authors.initials: C
authors.lastname: Frenette
authors.forename: Isabelle
authors.initials: I
authors.lastname: Mogck
authors.forename: Jonathan B
authors.initials: JB
authors.lastname: Gubbay
authors.forename: Alberto
authors.initials: A
authors.lastname: Severini
authors.forename: Joanne
authors.initials: J
authors.lastname: Hiebert
authors.forename: Shelley L
authors.initials: SL
authors.lastname: Deeks
authors.forename: Shaun K
authors.initials: SK
authors.lastname: Morris
mesh_terms: D002675:Child, Preschool; D016358:Contact Tracing; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D016867:Immunocompromised Host; D008297:Male; D008457:Measles / Q000209:etiology*; D022542:Measles-Mumps-Rubella Vaccine / Q000009:adverse effects*; D009864:Ontario; D015980:Public Health Practice; D014613:Vaccines, Attenuated / Q000009:adverse effects
chemical_list: D022542:Measles-Mumps-Rubella Vaccine; D014613:Vaccines, Attenuated