What is the recommended dose and administration of Immune Globulin (IG) for post-exposure prophylaxis against measles?

Measles Immune Globulin Post-Exposure Prophylaxis

Direct Recommendation

For post-exposure measles prophylaxis, administer intramuscular immune globulin (IG) at 0.25 mL/kg (maximum 15 mL) for immunocompetent individuals or 0.5 mL/kg (maximum 15 mL) for immunocompromised persons within 6 days of exposure, with MMR vaccine preferred if within 72 hours for those ≥6 months old. 1

Timing-Based Algorithm

Within 72 Hours of Exposure

• MMR vaccine is the preferred intervention for immunocompetent persons ≥6 months of age, as it may provide protection if given within this window 2, 1
• This applies even to household contacts aged 6-11 months, though these infants require revaccination after their first birthday 2
• MMR is contraindicated in immunocompromised persons and pregnant women for post-exposure prophylaxis 2

Between 72 Hours and 6 Days of Exposure

• IG becomes the primary intervention when the 72-hour window has passed 1
• IG can prevent or modify measles if administered within 6 days of exposure 2, 1

Beyond 6 Days of Exposure

• Neither IG nor MMR is effective for post-exposure prophylaxis at this point 2

Dosing by Patient Population

Immunocompetent Individuals

• Standard dose: 0.25 mL/kg intramuscularly (maximum 15 mL) 2, 1
• This applies to infants <12 months, household contacts, and other susceptible persons 2

Immunocompromised Patients

• Higher dose required: 0.5 mL/kg intramuscularly (maximum 15 mL) 2, 1
• Severely immunocompromised and symptomatic HIV-infected patients should receive IG regardless of vaccination status 2
• For patients on regular IGIV therapy, 100-400 mg/kg within 3 weeks before exposure is sufficient; if exposure occurs >3 weeks after IGIV, additional dosing should be considered 2

Alternative IGIV Dosing (When IM Volume is Problematic)

• Intravenous immunoglobulin: 400 mg/kg as a single dose 3, 4
• This route is particularly useful for recipients ≥30 kg where IM injection volume becomes impractical 3
• Multiple studies from 2018-2021 support IGIV at 400 mg/kg as equally or more effective than traditional IM dosing 3, 4, 5

Critical Follow-Up Requirement

Any person receiving IG must subsequently receive MMR vaccine 5-6 months after IG administration (if eligible for vaccination) 1, 6

• This delay is essential because passively acquired antibodies from IG interfere with vaccine immune response 1, 6
• Failure to provide this delayed vaccination leaves patients vulnerable to future exposures 1

High-Risk Groups Requiring IG Priority

IG is particularly indicated for susceptible household contacts at increased risk for complications 2, 1:

• Infants ≤12 months of age (especially <6 months who cannot receive MMR) 2, 1
• Pregnant women (MMR contraindicated) 2, 1
• Immunocompromised persons (may not respond to vaccine) 2, 1

Common Pitfalls and Caveats

Dosing Errors

• Using 0.25 mL/kg for immunocompromised patients instead of 0.5 mL/kg is inadequate and may result in prophylaxis failure 1
• The 15 mL maximum applies regardless of weight, which means patients >60 kg (for 0.25 mL/kg) or >30 kg (for 0.5 mL/kg) will not receive full weight-based dosing 2, 3

Declining IG Antibody Titers

• Modern IG products have lower measles antibody concentrations than historical preparations due to vaccine-derived immunity in blood donors 3, 4, 7
• A 2001 study found 57% of children developed measles despite IG when antibody titers were ≤16 IU/mL 7
• This has prompted international recommendations to increase dosing or use IGIV 3, 4

Practical Administration Challenges

• Multiple IM injections (2-8 sites) may be required for adequate dosing, which is traumatic for pediatric patients 8
• Clinical experience shows this can require sedation and is considered impractical by healthcare staff 8
• Consider IGIV (400 mg/kg) when IM volume exceeds practical limits 3, 8

Timing Misconceptions

• Measles is often not recognized until >72 hours after onset, making IG more commonly needed than vaccine for household contacts 2
• Do not confuse rubella (German measles) with rubeola (measles) – IG does not prevent rubella or mumps 1

Vaccination After IG

• Forgetting the 5-6 month delay before MMR administration is a critical error that either wastes vaccine (if given too early) or leaves patients unprotected (if never given) 1, 6