Catch-Up MMR Vaccination in Children
For children who have missed their MMR vaccines, administer 2 doses with a minimum interval of 4 weeks between doses, regardless of the child's current age or how much time has elapsed since they should have been vaccinated. 1, 2
Core Catch-Up Schedule
The fundamental principle is simple: there is no need to restart a vaccine series regardless of the time that has elapsed between doses. 1 This means if a child received one dose years ago and is now behind schedule, you simply give the next dose—you don't start over.
Minimum Age and Intervals
- Minimum age for first dose: 12 months 1, 2
- Minimum interval between doses: 4 weeks (28 days) 1, 2, 3
- If not previously vaccinated, administer 2 doses during any visit, with ≥4 weeks between doses 1
Age-Specific Catch-Up Guidance
For children 12 months through 12 years:
- Give the first dose immediately if never vaccinated 1, 2
- Give the second dose at least 4 weeks after the first dose 1, 2
- The second dose does not need to wait until age 4-6 years if the child is catching up 1, 2
For adolescents and adults:
- Older children and adolescents who missed the routine schedule should receive 2 doses separated by at least 4 weeks 4, 3
- Adults born in 1957 or later without documentation should receive at least one dose 4, 3
Vaccine Choice Considerations
First Dose in Children 12-47 Months
Use separate MMR and varicella vaccines rather than MMRV for the first dose in this age group. 1, 2 The CDC specifically recommends this approach because MMRV carries approximately one additional febrile seizure per 2,300-2,600 doses compared to separate vaccines in children aged 12-23 months. 2 Unless parents express a strong preference for MMRV after discussing risks and benefits, separate injections are preferred. 1, 2
Second Dose or First Dose ≥48 Months
MMRV is generally preferred over separate injections for the second dose at any age (15 months-12 years) or for the first dose at ≥48 months. 1, 2 The 47-month cutoff was selected because approximately 97% of febrile seizures occur in children ≤47 months of age. 2
Seizure History Precaution
Children with a personal or family history (sibling or parent) of seizures of any etiology should receive separate MMR and varicella vaccines instead of MMRV. 1, 2, 4
Special Situations
HIV-Infected Children
Asymptomatic HIV-infected children without severe immunosuppression should receive MMR vaccine as soon as possible upon reaching 12 months of age. 1 Consider administering the second dose as early as 28 days after the first dose rather than waiting until school entry. 1 However, MMR is contraindicated in severely immunocompromised children. 1, 2, 4
Early Vaccination Before 12 Months
If a child received MMR before 12 months of age (such as during travel or outbreak situations), this dose does not count toward the routine two-dose schedule. 4 The child still needs 2 doses starting at 12 months or later. 4 Research shows that vaccination before 8.5 months of age leads to markedly faster antibody decay and loss of protective levels over 6 years, so early vaccination should only be considered during outbreaks or high-risk situations. 5
Outbreak Control
During measles outbreaks, children with one MMR dose should receive the second dose as soon as possible with a minimum of one month between doses. 6 This accelerated schedule is appropriate for outbreak control even though it differs from routine guidelines. 6
Administration Logistics
MMR can be administered simultaneously with other vaccines at different anatomic sites. 4, 3 If not given simultaneously with other live vaccines, MMR should be administered at least 28 days before or after another live vaccine. 1, 4, 3
The two available MMR vaccines in the US (Priorix and M-M-R II) are fully interchangeable for all indications. 4, 3 You can use either vaccine for any dose without concern about switching products. 7
Common Pitfalls to Avoid
Don't delay catch-up vaccination waiting for the "ideal" age. If a child is behind, start immediately—the minimum 4-week interval is what matters, not reaching age 4-6 years. 1, 2
Don't restart the series if there's been a long gap. Time elapsed between doses doesn't matter; just continue where you left off. 1
Don't use MMRV reflexively for first doses in young children. The increased febrile seizure risk in the 12-47 month age group makes separate vaccines the preferred choice. 1, 2
Don't count doses given before 12 months of age. These must be repeated starting at 12 months or later. 4