Does Early MMR Vaccination Lead to Reduced Protection Against Measles?

You may have heard rumors that vaccinating with MMR prior to the first birthday can result in decreased efficacy of the vaccine. Some of that information may have come from a recent study, Long-term Dynamics of Measles Virus–Specific Neutralizing Antibodies in Children Vaccinated Before 12 Months of Age. Here’s what you should know:

• This is a very small study out of the Netherlands with 79 children vaccinated with MMR-0 between 6 and 12 months of age and MMR-1 at 14 months, and 44 children given MMR vaccine at 14 months (the recommended MMR vaccination schedule in the Netherlands is 14 months and 9 years, unlike the U.S. where the recommendation is 12 months and 4-6 years). Demographically, the two groups were very similar.
• Researchers performed blood antibody testing prior to MMR-1 and approximately 6 weeks, 1 year, and 3 years post MMR-1. Additional follow-up was done approximately 6 years after MMR-1 for 48 of the early-vaccinated children and 17 of the standard schedule children.
• Seven children who received an MMR-0 dose had neutralizing antibody levels below the seroprotection cutoff (i.e., they did not have protective antibody levels after the MMR-0 dose).
• Nearly all children who received an MMR-0 dose between 8.5 and 12 months and MMR-1 at 14 months or who received MMR-1 on the standard schedule at 14 months had protective antibodies above the seroprotection cutoff 5-6 years after vaccination.
• Most children who received an MMR-0 dose under 8.5 months of age had lower antibody levels that were below the seroprotection cutoff compared to those who received MMR-0 after 8.5 months of age or who did not receive an MMR-0 dose.
• Takeaways
  • This is a very small Dutch study that shows protection against measles may be suboptimal for infants given an MMR-0 dose before 8.5 months of age.
  • This study only looked at antibody levels and did not look at cellular immunity, which may still provide protection.
  • The standard MMR schedule in the Netherlands gives the second MMR vaccine at age 9, unlike the U.S. which recommends the second dose between age 4-6 years. This may make waning antibody levels at age 6 moot, as children would have been revaccinated.
  • Some children who failed to seroconvert to MMR-0 may have had vaccine failure, underscoring the importance of a repeat dose at 12 months and 4-6 years.

• Read the Long-term Dynamics of Measles Virus–Specific Neutralizing Antibodies in Children Vaccinated Before 12 Months of Age journal article.