Rabies is a deadly viral disease spread to humans through infected animal bites or scratches. While rabies infections in humans are rare in developed countries due to robust animal vaccination programs and public health measures, it remains a serious threat in developing nations where dog vaccination rates are low. Prompt post-exposure prophylaxis (PEP), which includes wound cleansing and rabies immunoglobulin or antiserum administration, is extremely effective in preventing the onset of clinical rabies if given immediately after an exposure. This article discusses rabies antiserum in detail and its vital role in rabies PEP.
What is Rabies Antiserum?
Rabies antiserum, also known as rabies immunoglobulin, is a component of rabies PEP. It contains rabies virus-neutralizing antibodies sourced from the blood plasma of vaccinated animals such as horses or humans. These high-titer antibodies provide immediate short-term passive immunity against the rabies virus until the host develops their own active immunity following vaccination. Rabies antiserum is manufactured through a complex process of vaccinating plasma donor animals, collecting their blood plasma rich in antibodies, and purifying and standardizing the immunoglobulin concentrate.
Mechanism of Action
After infiltration into bite wound sites and surrounding tissue through injections, rabies antiserum bind to any rabies virus particles present in the bite region. The bound antibodies will neutralize the virus and prevent it from infecting the exposed host’s cells and travelling to the central nervous system. This passive immunization bridges the gap between exposure to vaccination, allowing time for the host’s own active immunity to develop through post-exposure vaccinations. Studies show rabies antiserum improves chances of survival when used in conjunction with prompt wound cleansing and vaccination.
Importance of Timely Administration
Timely administration of rabies antiserum directly into and around wound sites is crucial for deriving its maximum protection benefits. This is because once the rabies virus enters the nervous system, antiserum cannot clear it. Hence, PEP must commence as soon as possible, ideally on the same day as exposure or within the first few days. The sooner neutralizing antibodies from antiserum are present at the exposure site, lesser is the chance of the virus spreading. Delays in administration significantly reduce antiserum effectiveness as the virus has more time to invade nerves and travel to the brain.
Quantity and Injection Sites
The recommended dose of rabies antiserum depends on the patient’s age, weight and exposure risk factors. It is typically 20 international units (IU) per kg body weight. For severe exposures like multiple deep bites, 40 IU per kg can be considered. Antiserum must infiltrate the entire wound area with deep injections around all bite, scratch or lick marks including surrounding unaffected tissue. If a sizable area is exposed, divided doses can be given. In case of open wounds, antiserum can be applied directly after cleansing. Post-exposure rabies vaccinations are started simultaneously or immediately after antiserum administration.
Availability and Cost
Major biosimilar rabies antiserum brands are manufactured by companies in countries such as India, China and France. However, availability can vary between regions globally depending on factors like local demand and supply chain management. In developing nations with suboptimal public health infrastructure, timely availability of antiserum for PEP may be hindered due to logistical challenges. The costs also differ between products and regions, ranging from as low as $30 per vial in lower-income countries to $200-300 per vial in high-income nations. For exposed individuals, timely access to affordable rabies antiserum is crucial to receiving complete PEP and preventing a fatal outcome.
Side Effects and Precautions
While rabies antiserum is generally well-tolerated when used as directed, minor adverse effects may rarely occur at the injection site like pain, swelling or skin reaction. Severe allergic reactions are exceedingly uncommon. As the antiserum is derived from animal plasma, there is a negligible theoretical risk of other transfusion-transmitted infections which modern large-scale manufacturing strives to eliminate through stringent screening of donor animals and purification processes. Standard precautions must be followed by health workers while handling or administering rabies antiserum. Those with a history of severe allergies to immune globulins must seek specialist advice before PEP.
Rabies antiserum forms the cornerstone of rabies post-exposure prophylaxis along with wound cleansing and vaccination. By providing immediate short-term passive immunity at exposure sites, it allows time for the host’s own active immunity to develop through vaccinations and prevents invasion of the rabies virus into the nervous system. Timely and appropriate administration of rabies antiserum in recommended doses directly into wound sites is critical for deriving its maximum protective benefits. Robust supplies of licensed rabies antiserum need to be ensured globally, especially in resource-constrained endemic areas to save lives at risk of rabies exposures.
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it