Human rabies immune globulin (HRIG) offers immediate, temporary protection against rabies, a severe and often fatal viral disease. Given the rapid progression of rabies, swift action after potential exposure is paramount. HRIG provides a temporary shield, allowing time for the body to develop its own sustained immune response. This temporary defense is a component of post-exposure prophylaxis, administered when someone may have been exposed to the rabies virus.
Understanding Human Rabies Immune Globulin
HRIG is a specialized preparation of antibodies collected from human plasma. These antibodies target and neutralize the rabies virus. The plasma is sourced from vaccinated human donors with high levels of rabies antibodies.
The manufacturing process involves purification and treatment of the pooled plasma to ensure product safety. This includes steps like cold alcohol fractionation, ion exchange chromatography, ultrafiltration, and viral inactivation methods. These processes aim to remove impurities and inactivate potential viruses. The final product is a sterile solution containing these pre-formed antibodies, ready for administration.
How HRIG Delivers Immediate Rabies Defense
HRIG provides “passive immunity.” This means that instead of stimulating the body to produce its own antibodies, HRIG directly supplies ready-made antibodies that immediately neutralize the rabies virus. These antibodies bind to the rabies virus at the site of exposure, preventing it from invading the nervous system and spreading throughout the body.
This immediate neutralization is important for rabies because the virus can progress rapidly once it enters the central nervous system, leading to severe and untreatable symptoms. HRIG acts as a temporary bridge, offering defense during the initial period after exposure. This allows sufficient time for the rabies vaccine, which is given concurrently, to stimulate the body’s own immune system to produce its long-lasting antibodies. Without this immediate intervention, the virus could spread before the vaccine’s effects take hold.
Receiving HRIG: What to Expect
HRIG is administered as a single dose as soon as possible after a potential rabies exposure, ideally at the same time as the first dose of the rabies vaccine. The recommended dosage for HRIG is 20 International Units per kilogram of body weight for individuals of all ages. It is important not to exceed this recommended dose, as higher amounts might interfere with the body’s own antibody production in response to the vaccine.
For visible wounds, as much of the HRIG dose is infiltrated directly into and around the bite or scratch site. This localized administration helps to neutralize the virus directly at the entry point. Any remaining portion of the HRIG is then administered as an intramuscular injection at a site distant from where the rabies vaccine is given. If there is no discernible wound, the entire dose is given intramuscularly.
Common side effects can include pain, redness, tenderness, or swelling at the injection site, as well as headache, fever, or muscle and joint pain. While rare, more severe allergic reactions, including anaphylaxis, can occur. Immediate medical attention is always advised following any potential rabies exposure.