Alternatives to Rabies Immune Globulin If You Can't Fill Your Prescription

Human rabies immune globulin (HRIG) is the gold standard for passive immunization in rabies post-exposure prophylaxis (PEP). But what if you are in a location where HRIG is unavailable — a rural area, overseas, or a facility that is out of stock? Are there alternatives?

The short answer: yes, alternatives exist, but they vary by availability, safety profile, and whether they are FDA-approved for use in the US. Here is what you need to know.

First: Can You Simply Use a Different Brand of HRIG?

Yes — and this is almost always the best first option. Three brands of human rabies immune globulin are FDA-approved and licensed in the United States:

HyperRAB (300 IU/mL) by Grifols: The most concentrated form; requires half the volume of the 150 IU/mL products for the same dose.

KedRAB / KEDRAB (150 IU/mL) by Kedrion/Kamada: FDA-approved since 2017, with a label update in 2021 establishing safety and effectiveness in children.

Imogam Rabies-HT (150 IU/mL) by Sanofi: A heat-treated formulation available since the 1970s; still widely used in hospital settings.

All three are equally effective at providing immediate passive immunity. If one brand is unavailable at a facility, they may be able to source a different brand. This is the safest and most effective option within the US.

What Is Equine Rabies Immune Globulin (ERIG)?

Equine rabies immune globulin (ERIG) is produced from the plasma of horses hyperimmunized with rabies vaccine, rather than human donors. It is widely used in developing countries where HRIG is unavailable or cost-prohibitive.

ERIG is administered at a higher dose than HRIG — 40 IU/kg versus 20 IU/kg for HRIG. It is generally considered safe when using purified preparations, with adverse reactions being rare and minor. However, unpurified ERIG has higher rates of serious reactions, including serum sickness and anaphylaxis.

Important: ERIG is not FDA-approved for use in the United States. If you receive PEP overseas with ERIG and then return to the US, consult with a travel medicine specialist or infectious disease physician to confirm your PEP regimen was adequate.

Monoclonal Antibodies: The Emerging Alternative

Monoclonal antibodies (mAbs) against the rabies virus are an exciting emerging alternative to HRIG. Unlike plasma-derived HRIG, mAbs are produced through biotechnology and offer several potential advantages:

Precise, consistent dosing with no variability from human donor pools

No risk of transmitting blood-borne pathogens (no human plasma involved)

Lower rates of adverse reactions compared to serum-derived products

Smaller doses needed due to precision targeting of the rabies virus

One leading candidate is TwinRab (docaravimab and miromavimab) — a two-mAb cocktail developed in collaboration with the WHO. In a 2025 clinical study of 159 patients with severe animal bites, the cocktail was well tolerated, with adverse events in only 10.7% of cases, all mild and local, and no rabies cases observed at 6-month follow-up.

However, monoclonal antibody alternatives to HRIG are not yet FDA-approved in the United States as of 2026. They have been approved for use as an alternative to rabies immunoglobulin in China and India since 2016. US patients cannot legally substitute mAbs for HRIG.

Can the Rabies Vaccine Replace HRIG?

Not directly — but timing matters. If HRIG is unavailable when you first arrive at a facility, you should still receive the first dose of rabies vaccine immediately. HRIG can then be administered up to and including Day 7 of the PEP series, as long as the vaccine has not yet had time to produce sufficient antibodies (which takes approximately 7-14 days).

After Day 7, HRIG is not indicated because the vaccine should have triggered your body's own antibody response. Administering HRIG too late could actually suppress the vaccine-induced immune response. Starting the vaccine series is always appropriate — do not wait for HRIG if it cannot be obtained immediately.

Who Should NOT Receive HRIG?

Some people do not need HRIG at all after an animal exposure:

People who have previously completed a full pre-exposure or post-exposure rabies vaccine series (and have a documented adequate antibody titer) should receive only 2 booster doses of rabies vaccine — no HRIG.

Administering HRIG to a previously vaccinated person is not recommended and may reduce the vaccine's effectiveness.

What to Do If You Cannot Access HRIG Right Away

If the first facility you visit does not have HRIG: (1) Start the vaccine series immediately. (2) Ask the facility to contact nearby hospitals or your state health department on your behalf. (3) Use medfinder to identify other nearby facilities that may stock HRIG. (4) Contact your county or state health department — they often have access to rabies biologics and can coordinate care.

Read our full guide: How to Find Rabies Immune Globulin in Stock Near You.