What should be done for a patient with immunity to Rubella (German measles) but susceptibility to measles?

Management of Patient with Immunity to Rubella but Susceptibility to Measles

The patient should receive one dose of MMR vaccine to address the measles susceptibility while maintaining rubella immunity. 1

Understanding the Laboratory Results

The laboratory results show:

• Rubella IgG: 642.0 IU/mL (Positive) - indicating immunity to rubella
• Measles IgG: 5.6 AU/mL (Negative) - indicating susceptibility to measles

Vaccination Recommendation

Primary Approach

1. Administer one dose of MMR vaccine immediately

   • Even though the patient is immune to rubella, the MMR vaccine is recommended to address measles susceptibility 2, 1
   • There is no standalone measles vaccine available in the US
   • Receiving additional rubella antigen when already immune is not harmful 1

2. No need for post-vaccination antibody testing

   • Follow-up serologic testing after vaccination is not recommended by CDC and ACIP guidelines 1
   • The MMR vaccine is highly effective, with a single dose providing approximately 95% protection against measles 2

Special Considerations

• For healthcare workers: If the patient works in healthcare, a second dose of MMR would be recommended, separated by at least 28 days from the first dose 2

• For women of childbearing age: The positive rubella immunity is particularly important. Rubella infection during pregnancy can cause congenital rubella syndrome 2

• For individuals born before 1957: While generally presumed immune to measles, during outbreaks or in healthcare settings, vaccination may still be recommended despite birth year 2

Rationale for Recommendation

1. Measles is highly contagious with significant morbidity and mortality risks

   • Complications include pneumonia, encephalitis, and death
   • Susceptible individuals have >90% chance of infection if exposed 1

2. MMR is a live vaccine that is safe and effective

   • Receiving additional doses when already immune to one component poses no increased risk 1
   • The benefit of measles protection outweighs any minimal risk from revaccination 1

3. Immunity persistence

   • Studies show that measles antibodies persist in vaccinated individuals for decades, though some may have waning immunity 1
   • The negative measles result indicates a clear need for vaccination regardless of prior vaccination history 3

Common Pitfalls to Avoid

• Do not order IgM testing unless acute infection is suspected. IgM testing is inappropriate for immunity screening and is frequently misused 3

• Do not delay vaccination while waiting for additional testing or documentation of previous vaccination history

• Do not administer individual component vaccines as they are not available in the US; MMR is the standard vaccine even when immunity to one component exists

• Do not assume immunity based on age or history without serologic confirmation, as demonstrated by this patient's mixed immunity status 4

By following this approach, you will provide optimal protection against measles while maintaining the patient's existing immunity to rubella, thereby reducing the risk of serious infectious disease complications.