MMR Vaccination for Infants 6 Months to Less Than 12 Months of Age

• While the MMR vaccine is safe for infants less than 12 months of age, with only mild side effects seen in most cases, it is not routinely recommended. Infants who receive a dose before 12 months of age should still receive two additional doses following the typical childhood vaccine schedules.
• MMR vaccination before 12 months of age can provide short-term protection during times of increased risk of being exposed to measles, but may not provide lasting protection. This can be due to interference from maternal antibodies or other mechanisms that are not as well understood.
  • This risk may be higher in patients who received their first dose of MMR before 8.5 months of age, with one study finding over 70% of children vaccinated before 8.5 months of age lost their protective antibodies levels within 6 years despite having received a repeat MMR dose at 14 months of age (van der Staak et al., 2025).
• Administration of MMR vaccines before 12 months of age should be reserved for use only when the risk of getting measles outweighs the potential risk of impaired long-term immunity.
  • When MMR is indicated for travel in patients less than 12 months of age, delaying vaccination until 2 - 3 weeks prior to travel may be beneficial in some cases, especially if this allows the infant to receive the MMR vaccination at 8.5 months of age or older while still meeting the recommended 2 weeks or more prior to travel.
• Additional information on MMR vaccinations in patients less than 12 months of age can be found in the following resources: 
  • Long-term dynamics of measles virus-specific neutralizing antibodies in children vaccinated before 12 months of age (van der Stakk et al., 2025) 
  • Effect of early measles vaccination on long-term protection: A systematic review (Xu et al., 2021)
  • Immunogenicity and reactogenicity following MMR vaccination in 5–7-month-old infants: a double-blind placebo-controlled randomized clinical trial in 6540 Danish infants (Vittrup et al., 2024)
  • Effect of measles vaccination in infants younger than 9 months on the immune response to subsequent measles vaccine doses: a systematic review and meta-analysis (Nic Lochlainn et al., 2019) 

These pathways do not establish a standard of care to be followed in every case. It is recognized that each case is different, and those individuals involved in providing health care are expected to use their judgment in determining what is in the best interests of the patient based on the circumstances existing at the time. It is impossible to anticipate all possible situations that may exist and to prepare a pathway for each. Accordingly, these pathways should guide care with the understanding that departures from them may be required at times.