Should an 18-month-old child with a fever and congested throat receive the Measles, Mumps, and Rubella (MMR) vaccine now or postpone it until recovery?

MMR Vaccination in an 18-Month-Old with Fever and Congested Throat

Give the MMR vaccine now (Option A) – this child's presentation represents a minor illness with low-grade fever that is NOT a contraindication to vaccination. 1

Clinical Assessment of Illness Severity

The key decision point is determining whether this child has a "minor illness" versus "moderate or severe febrile illness":

• Fever of 38.9°C (102°F) with congested throat and "slightly ill" appearance constitutes a minor illness, not a moderate-to-severe febrile illness 1
• The ACIP guidelines explicitly state that "minor illnesses, with or without fever (e.g., diarrhea, upper respiratory infection, otitis media) are NOT contraindications for vaccination" 1
• Vaccination should not be postponed for minor illnesses 1

Evidence Supporting Vaccination During Minor Illness

Seroconversion rates for MMR vaccine components among persons with mild febrile illness are similar to those among healthy persons 1

The guidelines emphasize that:

• Medical personnel should use every opportunity to vaccinate susceptible children, especially when compliance with follow-up cannot be assured 1
• Routine physical examinations or measuring temperatures are not prerequisites for vaccinating children who appear to be in good health 1

When to Defer Vaccination

Vaccination should be deferred only for moderate or severe febrile illnesses 1:

• This deferral avoids superimposing adverse vaccine effects on the underlying illness 1
• It prevents mistakenly attributing manifestations of the underlying illness to the vaccine 1

A child who "looks slightly ill" with an upper respiratory infection does not meet criteria for moderate-to-severe illness 1

Why Other Options Are Incorrect

• Option B (postpone): Incorrect because minor illnesses are explicitly NOT contraindications 1
• Option C (MMR without rubella): This option doesn't exist – MMR is a combined vaccine and cannot be given without one component 1
• Option D (delay until 4 years): Completely inappropriate – this would leave the child unprotected during high-risk years and contradicts all vaccination schedules 1

Common Pitfall to Avoid

Do not confuse "any fever" with "moderate-to-severe febrile illness" – the presence of low-grade fever alone does not warrant postponement if the child otherwise appears only mildly ill with an upper respiratory infection 1