Measles vaccine virus mutation following vaccination in a healthy child resulting in a false negative vaccine specific PCR test: Ontario, Canada, 2025

Euro Surveill. 2025 Oct;30(43):2500774. doi: 10.2807/1560-7917.ES.2025.30.43.2500774.

Abstract

We report a case of a mild, self-limited rash illness in a child 18 days after measles-mumps-rubella-varicella vaccination. Initial testing with a PCR-based method failed to detect vaccine virus. Sequencing later identified a novel mutation in the probe-binding site of the vaccine assay that had arisen after vaccination and resulted in the false-negative PCR test results.

Keywords: measles; measles diagnostic testing; measles vaccine.

Publication types

  • Case Reports

MeSH terms

  • Chickenpox Vaccine* / administration & dosage
  • Chickenpox Vaccine* / adverse effects
  • Exanthema
  • False Negative Reactions
  • Female
  • Humans
  • Infant
  • Male
  • Measles virus* / genetics
  • Measles virus* / immunology
  • Measles virus* / isolation & purification
  • Measles* / diagnosis
  • Measles* / prevention & control
  • Measles* / virology
  • Measles-Mumps-Rubella Vaccine* / administration & dosage
  • Measles-Mumps-Rubella Vaccine* / adverse effects
  • Mutation*
  • Ontario
  • Polymerase Chain Reaction* / methods
  • Vaccination / adverse effects
  • Vaccines, Combined

Substances

  • Measles-Mumps-Rubella Vaccine
  • Chickenpox Vaccine
  • measles, mumps, rubella, varicella vaccine
  • Vaccines, Combined