MMR Vaccine Schedule for Children 6 Years Old and Below

All children should receive two doses of MMR vaccine: the first dose at 12-15 months of age and the second dose at 4-6 years of age. 1, 2

Standard Two-Dose Schedule

Administer the first MMR dose at 12-15 months of age (minimum age: 12 months) 1, 2
This timing balances maternal antibody waning with the need for early protection against wild-type measles, which carries risk of serious complications including subacute sclerosing panencephalitis (SSPE) 2

Administer the second MMR dose at 4-6 years of age, ideally before school entry 1, 3
The second dose may be given earlier than 4-6 years, provided at least 28 days (4 weeks) have elapsed since the first dose 1
The 4-6 year timing helps prevent school-based measles outbreaks, as most vaccine failures are due to non-response to the first dose 3

Minimum interval between doses: 28 days (4 weeks) 1
While 28 days is the minimum acceptable interval, the routine recommendation is to wait until 4-6 years for the second dose unless catch-up vaccination is needed 1

PRIORIX and M-M-R II are fully interchangeable MMR vaccines that can be used for any dose 1
Both vaccines have similar safety, immunogenicity, and efficacy profiles 1, 4, 5

For children aged 12-47 months (first dose):

CDC recommends separate MMR and varicella vaccines rather than MMRV unless parents specifically request MMRV after discussing risks and benefits 1, 6
MMRV carries approximately one additional febrile seizure per 2,300-2,600 doses compared to separate vaccines in children aged 12-23 months during days 5-12 post-vaccination 1, 6
A personal or family history (sibling or parent) of seizures is a precaution for MMRV use 1, 6

For children aged 48 months and older (≥4 years):

MMRV vaccine is generally preferred over separate injections for the second dose at any age or first dose at ≥48 months 1, 6, 7
Post-licensure studies showed no increased febrile seizure risk in children aged 4-6 years receiving MMRV 7

Infants aged 6-11 months traveling internationally should receive a single dose of MMR before travel 1
This early dose does not count toward the routine two-dose series; the child still needs two additional doses starting at 12-15 months 1

During measles outbreaks, infants aged 6-11 months should receive a single dose of MMR 1
For measles postexposure prophylaxis, administer MMR within 72 hours of exposure to unvaccinated persons, then complete the two-dose series ≥28 days later 1

All children 11-12 years of age should have documentation of two MMR doses received after their first birthday 1, 3
Previously unvaccinated children can start the series at any age ≥12 months, with doses separated by at least 28 days 1

MMR can be administered simultaneously with other routine childhood vaccines at different anatomic sites 1, 5
If not given simultaneously, live vaccines (including MMR and varicella) must be separated by ≥28 days 6
MMR has been safely co-administered with DTaP-IPV, varicella, pneumococcal conjugate, and hepatitis A vaccines without interference 1, 5

The two-dose schedule is essential because most measles vaccine failures result from non-response to the first dose, not waning immunity 3
School entry requirements mandate two documented MMR doses to prevent outbreaks in high-transmission settings 3
Both PRIORIX and M-M-R II provide equivalent protection; having two manufacturers safeguards vaccine supply 1
SSPE is caused exclusively by wild-type measles virus, not vaccine strains—MMR vaccine does not cause SSPE 2