Rabies Immune Globulin Side Effects: What to Expect and When to Call Your Doctor

Receiving human rabies immune globulin (HRIG) as part of post-exposure prophylaxis (PEP) is a critical step in preventing rabies. Like all medications, HRIG can cause side effects — but for most patients, these are mild and resolve quickly. Understanding what to expect can help you know when to simply rest and when to seek further medical attention.

Common Side Effects of Rabies Immune Globulin

In clinical trials for HyperRAB, the most common adverse reactions (occurring in more than 5% of subjects) were:

Injection site pain: The most frequently reported side effect. Can range from mild soreness to more significant pain, especially when HRIG is infiltrated into and around a wound. Multiple injection sites may be used for large wounds.

Injection site nodule: A small, firm lump at the injection site. Usually resolves on its own within days to weeks.

Headache: A common systemic reaction following immune globulin administration. Usually mild and manageable with over-the-counter pain relievers like acetaminophen or ibuprofen.

Abdominal pain, diarrhea, and flatulence: Gastrointestinal side effects are reported in some patients. These typically resolve without intervention.

Nasal congestion: A mild upper respiratory symptom that may occur following administration.

These common side effects are generally self-limiting and do not require stopping treatment or medical intervention. Non-steroidal anti-inflammatory drugs (NSAIDs) or acetaminophen can help manage injection site pain and headache.

Serious Side Effects: When to Get Emergency Help

While rare, HRIG can cause serious adverse reactions that require immediate medical attention. Call 911 or seek emergency care immediately if you experience:

Anaphylaxis (severe allergic reaction): Signs include hives, difficulty breathing, swelling of the face or throat, hoarseness, severe itching, or fainting. This is a life-threatening emergency. Facilities administering HRIG keep epinephrine (EpiPen) available for this reason.

Thromboembolism (blood clots): Symptoms may include swelling and pain in arms or legs, chest pain, shortness of breath, or sudden numbness/confusion. Rare but reported with immune globulin products.

Hemolysis (breakdown of red blood cells): Signs include fatigue, pale or yellowed skin, dark urine, or shortness of breath. Monitor for these in the days following injection.

Aseptic meningitis: Rare. Symptoms include severe headache, fever, stiff neck, sensitivity to light, and nausea. Seek immediate care if these symptoms appear within days of HRIG administration.

Who Is at Higher Risk for Adverse Reactions?

Some patients have a higher baseline risk of adverse reactions to HRIG:

Patients with IgA deficiency: Patients with isolated immunoglobulin A (IgA) deficiency may develop severe hypersensitivity reactions to HRIG, or subsequently to any blood product containing IgA. Clinicians should assess IgA status in patients with known immune deficiencies.

History of prior allergic reactions to human immunoglobulins: Patients who have previously had systemic allergic reactions to any immune globulin preparation are at greater risk of anaphylaxis with HRIG.

Tell your provider about any history of allergic reactions to blood products or immune globulins before receiving HRIG. The treating facility should always have epinephrine available.

Can HRIG Interfere With Other Vaccines?

Yes. Because HRIG contains a concentrated pool of human antibodies, it can blunt the immune response to certain live vaccines. Important timing rules:

Wait at least 4 months after receiving HRIG before getting a measles vaccine.

Wait at least 3 months for other live vaccines (mumps, rubella, polio, rotavirus, typhoid, yellow fever, varicella).

This does NOT apply to the rabies vaccine itself — HRIG is specifically designed to be given alongside the rabies vaccine and does not significantly suppress the rabies vaccine's immune response when administered at the correct dose.

HRIG and Pregnancy or Breastfeeding

Pregnancy is not a contraindication for rabies PEP. Rabies is a fatal disease, and the benefits of PEP far outweigh any theoretical risks to a pregnancy. HRIG may cross the placenta (as immunoglobulins typically do) and may be distributed into breast milk. There are no adequate studies specifically evaluating HRIG in pregnant or breastfeeding patients — the clinical decision to proceed with PEP should always be made based on the risk of untreated rabies versus any theoretical risk.

What About Blood-Borne Disease Transmission Risk?

HRIG is made from human plasma, which theoretically carries a risk of transmitting infectious agents. All licensed US HRIG products undergo rigorous donor screening, testing of individual donations and plasma pools, and multiple viral inactivation steps during manufacturing (solvent/detergent treatment in KedRAB and HyperRAB S/D, heat treatment in Imogam Rabies-HT, caprylate chromatography in HyperRAB). The risk of blood-borne disease transmission from HRIG is considered extremely low, but not zero.

Also see our guide on Rabies Immune Globulin Drug Interactions for more on what to avoid and what to tell your doctor.

If you need help finding a facility near you that can administer HRIG, visit medfinder.com.