Can the Measles, Mumps, and Rubella (MMR) vaccine and the Varicella (chickenpox) vaccine be administered less than 28 days apart?

MMR and Varicella Vaccine Administration Timing

MMR and varicella vaccines should not be administered less than 28 days apart unless given on the same day. 1

Recommended Administration Schedule

• If not administered on the same day, MMR and varicella vaccines should be separated by at least 28 days 1
• When administered on the same day, MMR and varicella vaccines produce immune responses identical to vaccines administered a month apart 1
• For children 12 months through 12 years of age, both vaccines can be administered simultaneously at the same visit 1

Scientific Rationale

• Live virus vaccines given by the parenteral route may interfere with each other's immune response if administered less than 28 days apart 1
• Administering two or more live-virus vaccines parenterally within 28 days of each other (rather than simultaneously) may result in an impaired immune response 1
• This recommendation is based on immunological principles and extensive clinical experience that have strengthened the scientific basis for administering vaccines simultaneously 1

Exceptions and Special Considerations

• If the second dose of varicella vaccine is administered inadvertently between 28 days and 3 months after the first dose in children aged 12 months through 12 years, the second dose does not need to be repeated 1
• For persons aged ≥13 years, the recommended minimum interval between two doses of varicella vaccine is 4 weeks 1
• MMRV (combined measles-mumps-rubella-varicella) vaccine can be used to administer all four vaccines simultaneously in eligible children 12 months through 12 years of age 1

Clinical Implications

• Simultaneous administration of all vaccines for which a person is eligible is critical to ensure complete protection and reduce missed vaccination opportunities 1
• A study conducted during a measles outbreak demonstrated that approximately one-third of measles cases among unvaccinated but vaccine-eligible preschool children could have been prevented if MMR had been administered at the same visit when another vaccine was administered 1
• Both MMR and varicella vaccines are administered via the subcutaneous route 1

Practical Approach

• If a patient presents for vaccination:
  • Option 1: Administer both MMR and varicella vaccines at the same visit 1
  • Option 2: If unable to administer both vaccines at the same visit, schedule the second vaccine at least 28 days after the first 1
• For documentation purposes, only doses of vaccine with written documentation of the date of administration should be considered valid 1

Common Pitfalls to Avoid

• Administering live virus vaccines less than 28 days apart (except on the same day) may result in suboptimal immune response 1
• Delaying vaccination increases the risk of disease exposure during the unprotected interval 1
• Failing to document vaccination dates properly may lead to unnecessary revaccination 1