MMR Vaccination in an 18-Month-Old with Mild Febrile Illness
Give the MMR vaccine now—this child's fever of 38.9°C (102°F) with congested throat and slightly ill appearance constitutes a minor illness, which is not a contraindication to vaccination. 1, 2
Evidence-Based Rationale
Minor Illness Does Not Contraindicate Vaccination
The Advisory Committee on Immunization Practices (ACIP) explicitly states that minor illnesses with or without fever—including upper respiratory infections, diarrhea, and otitis media—are not contraindications for MMR vaccination and that vaccination should not be postponed because of them. 1, 2
Seroconversion rates for each component of MMR vaccine among persons with mild febrile illness are similar to those among healthy persons, meaning the vaccine will work just as effectively. 1, 2
Medical personnel should use every opportunity to vaccinate susceptible children, particularly when compliance with follow-up visits cannot be assured. 1, 2
When to Defer Vaccination
Vaccination should be deferred only for moderate or severe febrile illnesses—not the mild presentation described in this case. 1, 2
The purpose of deferring in moderate-to-severe illness is to avoid superimposing adverse vaccine effects on the underlying illness and to prevent mistakenly attributing manifestations of the underlying illness to the vaccine. 1
Data are generally not available regarding safety and immunogenicity of MMR among persons with moderate or severe febrile illness, which is why deferral is recommended in those cases. 1
Practical Implementation
In childhood vaccination programs, appropriate procedures include asking the parent if the child is ill, postponing vaccination only for children with moderate or severe febrile illnesses, and vaccinating children who do not have other contraindications. 1
Routine physical examinations or measuring temperatures are not prerequisites for vaccinating persons who appear to be in good health. 1
This 18-month-old with low-grade fever and congestion who "looks slightly ill" clearly falls into the minor illness category and should receive MMR now. 1, 2
Why Other Options Are Incorrect
Postponing until recovery (Option B) contradicts ACIP guidelines and risks missing a critical vaccination opportunity, potentially leaving the child susceptible during a vulnerable period. 1, 2
Giving MMR without rubella subunit (Option C) is not medically indicated or available—there is no medical basis for administering separate antigens instead of the preferred MMR combined vaccine for routine vaccination. 1
Delaying until 4 years (Option D) is inappropriate and dangerous, as it leaves the child unprotected against measles, mumps, and rubella for an extended period when the first dose is recommended at 12-15 months. 1