MMR Booster for Isolated Mumps Non-Immunity
Yes, this patient needs an MMR booster dose. When a patient lacks immunity to mumps but is immune to measles and rubella, they should receive an additional dose of MMR vaccine to establish mumps protection, as documented age-appropriate vaccination is the goal regardless of selective immunity to individual components 1, 2.
Why This Patient Needs Vaccination
The presence of measles and rubella immunity does not contraindicate MMR administration. The ACIP explicitly states that MMR vaccine can and should be given when indicated for any of its three components, even when immunity exists to the other components 2. There is no increased risk of adverse events from administering MMR to persons already immune to one or more component viruses 2, 3.
Key Principle: Documented Vaccination Supersedes Serology
The 2011 ACIP guidelines establish a critical concept: documented age-appropriate vaccination supersedes subsequent serologic testing results 1. However, this principle applies when proper vaccination has been documented—if this patient's mumps non-immunity suggests incomplete vaccination history, they require additional dosing 1.
Clinical Decision Algorithm
Step 1: Verify vaccination history
- If the patient has documented receipt of 2 doses of MMR vaccine given at appropriate intervals (at least 28 days apart, both after first birthday), they should be considered immune to mumps regardless of negative serology 1
- If vaccination history is uncertain, incomplete, or shows only 1 dose, proceed to Step 2 1
Step 2: Assess risk category
- High-risk groups requiring 2 doses: healthcare personnel, students in post-secondary educational institutions, international travelers 1, 4
- Standard-risk adults: generally require 1 dose if born in 1957 or later 1
Step 3: Administer MMR vaccine
- Give MMR vaccine (not individual mumps vaccine, as MMR is the vaccine of choice) 1
- Document this dose as part of the patient's permanent vaccination record 1
- No serologic testing is needed after vaccination 1
Why Not to Repeat Serology
Do not administer additional MMR doses based solely on negative mumps titers in properly vaccinated individuals. The 2011 ACIP guidelines specifically state that healthcare personnel who are tested serologically and found to have negative or equivocal mumps titers should NOT receive an additional dose if they have documented age-appropriate vaccination—such persons should be considered immune 1. This recommendation prioritizes vaccination documentation over serologic results because mumps antibody testing has limitations in predicting true immunity 1.
Safety Considerations
Administering MMR to someone already immune to measles and rubella is completely safe. Side effects occur almost exclusively among vaccine recipients who are non-immune and are very rare after revaccination 3. No evidence exists that persons previously immune to any MMR component are at increased risk for local or systemic reactions 3.
Common Pitfall to Avoid
Never chase titers with repeated MMR doses in fully vaccinated individuals. If this patient has documented receipt of 2 appropriately-spaced doses of MMR vaccine after their first birthday, they should be considered immune to mumps regardless of serology, and no additional dose is recommended 1. The exception is during mumps outbreaks in healthcare settings, where exposed healthcare personnel with only 1 documented dose should receive a second dose 1.
Special Circumstances Requiring Action
During mumps outbreaks: Healthcare personnel with no evidence of mumps immunity who are exposed should be offered MMR vaccine and excluded from duty from day 12 through day 25 after exposure 1. Those with only 1 documented dose should receive the second dose and may remain at work 1.
For international travelers: A second dose of MMR is recommended for persons traveling to measles-endemic areas, even if they have documented immunity to rubella, because the risk of measles exposure is substantially elevated 2.