What is the recommended post-exposure prophylaxis (PEP) for individuals exposed to measles, including those with compromised immune systems or pregnant women?

Measles Post-Exposure Prophylaxis

Primary Recommendation

For most susceptible individuals ≥6 months of age exposed to measles, administer MMR vaccine within 72 hours of exposure; if beyond 72 hours but within 6 days, administer immune globulin (IG) instead. 1

Algorithm for Post-Exposure Management

Step 1: Determine Timing and Eligibility

Within 72 hours of exposure:

• MMR vaccine is preferred for susceptible persons ≥6 months of age in most settings (day care, schools, colleges, healthcare facilities, household contacts) 2, 1
• This approach is acceptable for household contacts ≥6 months except pregnant women, immunocompromised patients, and those with other vaccine contraindications 2, 1

Beyond 72 hours but within 6 days of exposure:

• IG becomes the intervention of choice as vaccine efficacy diminishes after the 72-hour window 1, 3
• Measles is often not recognized until >72 hours after onset, making IG more practical for household contacts 2, 1

Step 2: Identify Special Populations Requiring IG Regardless of Timing

Immunocompromised patients:

• Always use IG at 0.5 mL/kg IM (maximum 15 mL) regardless of timing or vaccination status 2, 1, 3
• This is double the standard dose due to impaired immune response 1, 3
• MMR vaccine is contraindicated for post-exposure prophylaxis in this population 2, 1

Pregnant women:

• Administer IG at 0.25 mL/kg IM (maximum 15 mL) within 6 days of exposure 2, 4
• MMR vaccine is absolutely contraindicated in pregnancy due to theoretical teratogenic risks from live virus 4
• Monitor for measles symptoms for 21 days post-exposure (fever, cough, coryza, conjunctivitis, followed by maculopapular rash) 4

Infants <6 months:

• Administer IG at 0.25 mL/kg IM (maximum 15 mL) as they are below the threshold for vaccine administration 2, 1, 3
• Infants <6 months are usually immune from maternal antibodies, but if measles is diagnosed in the mother, all unvaccinated children in the household should receive IG 2

Infants 6-12 months:

• MMR vaccine within 72 hours is preferred 1
• If identified after 72 hours but within 6 days, use IG at 0.5 mL/kg IM (updated dosing based on declining antibody concentrations in current IG products) 5

Step 3: Standard IG Dosing for Immunocompetent Individuals

• Standard dose: 0.25 mL/kg IM (maximum 15 mL) for immunocompetent persons 2, 1, 3
• Immunocompromised dose: 0.5 mL/kg IM (maximum 15 mL) 2, 1, 3
• Alternative for large patients or volume concerns: IVIG 400 mg/kg can be considered, particularly for recipients ≥30 kg where IM volume becomes impractical 5, 6, 7
• For patients receiving regular IGIV therapy, ≥100 mg/kg within 3 weeks before exposure should be sufficient for protection 2, 1

Critical Follow-Up Requirements

Post-IG vaccination schedule:

• Any person who receives IG must subsequently receive MMR vaccine 5-6 months later (if ≥12 months old and vaccine not contraindicated) 2, 1, 3
• This delay is mandatory because passively acquired antibodies from IG interfere with vaccine response 2, 1, 3
• Failure to provide delayed MMR vaccination leaves the patient vulnerable to future exposures 3

Infants vaccinated before 12 months:

• Must be revaccinated with two doses of MMR starting at ≥12 months of age, separated by at least 28 days 2, 1
• This applies to any infant who received MMR before their first birthday for post-exposure prophylaxis 2, 1

Postpartum vaccination for pregnant women:

• Administer MMR vaccine before hospital discharge if the woman remains non-immune and has no contraindications 4
• If IG was given during pregnancy, delay MMR until 5-6 months post-IG administration 4
• Breastfeeding is not a contraindication to MMR vaccination 4

Common Pitfalls to Avoid

Do not use IG for outbreak control:

• IG should not be used to control measles outbreaks in the general population; MMR vaccine is preferred for this purpose 2, 1

Do not confuse measles (rubeola) with rubella:

• IG does not prevent rubella or mumps infection after exposure and is not recommended for those purposes 2, 4
• Administering IG after rubella exposure may modify symptoms but creates false security 2

Do not use standard IG dosing for immunocompromised patients:

• The higher dose of 0.5 mL/kg is essential for this population, not the standard 0.25 mL/kg 1, 3

Do not administer MMR to contraindicated populations within 72 hours:

• Even within the 72-hour window, pregnant women and immunocompromised patients require IG, not MMR 2, 1, 4

Do not assume household contacts will be identified within 72 hours:

• Measles is often not recognized until after the 72-hour window, making IG the more practical intervention for household contacts 2, 1

Evidence Quality Considerations

Recent systematic review data (2025) shows measles infection rates of 0-30% with IG PEP and 0-15% with MCV PEP, with effectiveness estimates ranging from 76-100% for IG and 83.4-100% for MCV 8. However, declining measles antibody concentrations in current immunoglobulin products (due to increased proportion of vaccinated donors versus naturally immune donors) has prompted updated dosing recommendations, particularly the consideration of higher IG doses or IVIG in certain populations 5, 6. A 2021 Austrian outbreak study demonstrated 99.3% effectiveness (95% CI: 88.7-100%) with IVIG 400 mg/kg in infants, with no serious adverse events 7.