Measles Outbreak Risk Assessment and Response

General Principles

• The Centers for Disease Control and Prevention (CDC) considers any community with suboptimal vaccination coverage to be at significant risk for measles outbreaks, as a single confirmed case constitutes an urgent public health situation requiring immediate intervention 1, 2
• The CDC recommends immediate action when any suspected measles case occurs, as one confirmed case represents an urgent public health situation 1, 2

Key Risk Factors and Outbreak Response

• Areas are considered high-risk for measles when they have large inner city populations, recent measles outbreaks among unvaccinated preschool-aged children, or more than five measles cases among preschool-aged children during each of the last 5 years 3, 4
• Approximately 5% of children who receive only one dose of MMR vaccine fail to develop immunity, creating pockets of susceptibility 3, 5
• All persons without acceptable evidence of immunity should be vaccinated or excluded from outbreak settings, such as schools, day care facilities, hospitals, and clinics 1, 6, 7

Vaccination Requirements and Outbreak Control

• Prompt vaccination of susceptible persons at risk for exposure may prevent dissemination 1, 2
• Mass revaccination of entire communities is generally not necessary 1, 7
• Persons exempted from vaccination for any reason must be excluded from involved institutions until 21 days after rash onset in the last case 1, 6, 7

Common Pitfalls to Avoid

• Do not assume birth before 1957 guarantees immunity—during outbreaks, MMR vaccination should be considered for pre-1957 individuals who may be exposed 3, 4
• Do not delay outbreak control measures while waiting for laboratory confirmation 1, 2