Human Rabies Immunoglobulin

Human rabies immunoglobulin is a plasma-derived immunoglobulin preparation containing purified human antibodies that specifically neutralize rabies virus. It belongs to the class of specific human immunoglobulins and provides passive immunity rather than stimulating the patient's immune system to produce its own antibodies. After administration following a potentially rabies-infectious exposure, the antibodies provide immediate local and systemic protection while rabies vaccination stimulates the development of active, longer-lasting immunity. Human rabies immunoglobulin is administered as part of post-exposure prophylaxis, primarily by careful infiltration into and around the exposure wound; depending on the product and applicable guidance, any remaining calculated dose may be administered intramuscularly at a site separate from the vaccine. The recommended human rabies immunoglobulin dose is generally limited to 20 IU/kg body weight. It is particularly important for people with severe, category III exposures who have not previously completed an appropriate rabies vaccination course. Human rabies immunoglobulin does not replace rabies vaccine and is normally administered only once during post-exposure prophylaxis. Because clinical rabies is almost invariably fatal after symptoms develop, timely wound care, appropriate vaccination and indicated immunoglobulin administration are critical components of prevention.

Human rabies immunoglobulin was developed as a specific passive-immunisation product using purified antibodies obtained from human plasma containing high levels of rabies-neutralising antibodies. Regulatory standards for human rabies immunoglobulin have been established internationally to address potency, safety, plasma sourcing and manufacturing quality. The EMA adopted its Core Summary of Product Characteristics guideline for human rabies immunoglobulin for intramuscular use under reference CPMP/BPWG/3728/02, with a legal effective date of 1 February 2006. Human rabies immunoglobulin products are generally authorised through national regulatory procedures rather than through a single centralised EMA marketing authorisation. In the European Union, nationally authorised human rabies immunoglobulin products are subject to ongoing regulatory review. In 2024, the EMA also agreed a paediatric investigation plan for a human rabies immunoglobulin product intended for prevention of rabies viral infection by intramuscular administration. Clinical development and regulatory evaluation have focused on rabies virus-neutralising antibody activity, pharmacological protection and use as part of post-exposure prophylaxis rather than treatment of established symptomatic rabies.

Human rabies immunoglobulin is used for post-exposure prophylaxis after potentially rabies-infectious exposure in people who require passive immunisation. It is generally indicated for severe category III exposures in individuals who have not previously been appropriately vaccinated against rabies and is administered together with rabies vaccine. Depending on national guidance, rabies immunoglobulin may also be indicated for certain category II or III exposures in immunocompromised individuals and for specific high-risk exposures. It is intended to neutralize rabies virus at the exposure site while the rabies vaccine induces active immunity. Human rabies immunoglobulin is not used as routine pre-exposure prophylaxis, is not a substitute for rabies vaccination, and does not provide treatment for established clinical rabies after symptoms have developed.

Human rabies immunoglobulin is administered as a single dose of 20 IU/kg body weight for human rabies immunoglobulin. As much of the calculated dose as anatomically feasible should be infiltrated carefully into and around all accessible wounds after thorough wound cleansing. If the calculated volume is insufficient to infiltrate multiple wounds adequately, sterile normal saline may be used for appropriate dilution according to applicable guidance. Any remaining dose should be handled according to the specific product information and local rabies protocols; some protocols recommend intramuscular administration at a site separate from the rabies vaccine. Human rabies immunoglobulin should be given as soon as possible after the first rabies vaccine dose when indicated and should not ordinarily be administered later than 7 days after the first vaccine dose. The maximum recommended dose should not be exceeded. Rabies vaccine must continue according to the appropriate post-exposure schedule even when immunoglobulin is unavailable initially.

Human rabies immunoglobulin may cause local injection-site pain, tenderness, redness or swelling, particularly when a substantial amount is infiltrated around wounds. Temporary fever, headache, malaise or other mild systemic reactions may occur. Most reactions are generally short-lived and manageable under medical supervision. Because the product is administered after a potentially serious rabies exposure, local reactions should be distinguished from symptoms associated with the original injury or other components of post-exposure prophylaxis, particularly rabies vaccination.

Serious allergic reactions, including anaphylaxis, are uncommon but can occur and require immediate medical treatment. Human rabies immunoglobulin should not be injected into a blood vessel because inadvertent intravascular administration can cause serious reactions, including shock. Individuals with IgA deficiency may have an increased risk of reactions to some plasma-derived immunoglobulin preparations containing IgA. As with other plasma-derived medicinal products, manufacturing controls reduce the risk of transmission of infectious agents, but such risk cannot be considered absolutely zero. Because rabies is life-threatening, there are generally no absolute contraindications that justify withholding indicated rabies immunoglobulin after a significant exposure; treatment should instead be administered with appropriate precautions and emergency support available for severe reactions.

Before administration, clinicians should assess the exposure category, wound location and severity, previous rabies vaccination history and the timing of the exposure. Wounds should be thoroughly washed and flushed as soon as possible, ideally for at least 15 minutes, before immunoglobulin infiltration. Human rabies immunoglobulin should be administered separately from rabies vaccine and should not be mixed in the same syringe or injected at the same anatomical site as the vaccine. Classic drug interactions are uncommon because human rabies immunoglobulin is a purified antibody preparation, but passive antibodies can interfere with certain live-virus vaccines. Appropriate vaccination timing should therefore be considered when other live vaccines are planned. Immunocompromised patients require particular attention because their response to rabies vaccination may be reduced and national guidance may recommend additional measures.

Confirm the patient's weight, exposure category, previous rabies vaccination status and exact immunoglobulin concentration before calculating the dose. Thoroughly cleanse the wound before infiltration and distribute as much of the calculated dose as anatomically feasible into and around every relevant wound. For multiple or extensive wounds, appropriate dilution with sterile normal saline may facilitate adequate local infiltration. Do not exceed the recommended dose because excessive immunoglobulin can interfere with the immune response generated by rabies vaccination. Ensure that the immunoglobulin and rabies vaccine are administered at separate anatomical sites and that the complete vaccine schedule is continued. If rabies immunoglobulin is not immediately available, rabies vaccination should not be delayed; immunoglobulin can generally be administered as soon as possible within the permitted post-vaccination window. Emergency treatment for anaphylaxis should be readily available during administration.