Vetnews | September 2024 12 « BACK TO CONTENTS Article Prophylactic use of rabies vaccines Rabies is a devastating disease that is fatal in nearly 100% of cases. The primary source of human contraction is through a bite from a rabid animal; in these instances, there are vaccinations available for humans to be taken pre- and/or post-exposure to lower the fatality rate. The effectiveness of the pre-and post-prophylaxis vaccines when taken together is remarkably high, with no reported deaths due to rabies in any individual who has taken both; however, there was one reported death in an individual who had only the preexposure immunization with no post-exposure booster [26]. The pre-exposure prophylaxis (PrEP) vaccination is a safe vaccine that can be co-administered with other vaccines in children or can be given separately. The administration of the PrEP vaccination series involves three intramuscular or intradermal injections to prime the patient’s immune system; these injections are done on a standard schedule, and an injection is administered on days 0, 7, and 28 [27]. The purpose of this vaccine is to allow the immune system to exhibit recall when exposed to the virus in the event of a rabid animal bite [27]. Additionally, PrEP administration would decrease the amount of post-exposure vaccination an individual would have to receive in the event of an exposure [27]. This may not limit the cost of overall care per patient, but it most certainly would benefit patients in varying circumstances, such as in remote communities where post-exposure prophylaxis (PEP) is not readily available, in situations where risk of exposure is high and may not be recognized, in places where controlling rabies in the animal reservoir is difficult and where human exposure risk is high, and in occupations where animal interactions are frequent (i.e. bat handlers or zoologists) [27]. PrEP should also be included in the immunization of children in high-risk areas, followed by a booster after one year. The administration of the PEP treatment is determined via an assessment based on the risk of infection, the severity of infection, the site of the wound, the appearance of the wound, behavior, the fate of the biting animal, and the vaccination status of the biting animal [26]. An unusual contact with a bat, regardless of location, is a sufficient ground for considering rabies exposure [26]. Rabies exposure is considered as contact of the saliva of a rabid animal to broken skin or intact mucous membrane of the patient [26]. Under these circumstances, PEP is indicated in the patient, regardless of how long before the contact with animal saliva occurred, and the patient will undergo wound care, active immunization, and passive immunization. If a patient was previously immunized, a shorter booster regimen is given along with wound care. There are a multitude of vaccine regimens, both intramuscular and intradermal, that involve variable sites of injection and number of injections, requiring multiple clinical follow-ups to maintain a proper injection schedule[26]. Therapeutic applications of rabies vaccines and novel treatment modalities The current standard for PEP involves a combination of human rabies immunoglobulin (HRIG) and rabies vaccine administration [2]. In a prospective study from January 2021 to December 2021 at the Kempegowda Institute of Medical Sciences (KIMS) Hospital and Research Center, 123 category III animal bite victims provided clinical evidence of the safety and efficacy of HRIG in combination with an entire course of antirabies vaccinations for PEP [28]. HRIG provides immediate passive immunity by neutralizing the virus at the site of infection, while the rabies vaccine stimulates the immune system to produce long-lasting active immunity [28]. The most used vaccine in combination with HRIG is the inactivated or killed rabies virus vaccine [12]. Immunization against these inactivated vaccines develops over time due to the activation of helper and cytotoxic T cells, allowing for virus-neutralizing antibodies to be produced for long-lasting active immunity. These vaccines are administered globally [29]. The effectiveness of RIG and vaccine therapy in treating rabies infection is wellestablished, especially when administered promptly after exposure. In an open-label, single-arm study of 12 healthy adult subjects, Hanna et al. found that caprylate/chromatography purified HRIG (RIG-C) produced a rapid increase in rabies-neutralizing antibodies within 24 hours, peaked on day four and maintained through day 21 [30]. However, limitations exist with RIG administration, such as the worldwide availability of RIG, potential allergic reactions, and Vaccine Type Characteristics Route of Administration Target Population Limitations Inactivated rabies vaccine [10-13] Contains rabies virus inactivated via various chemicals Intramuscular injection Humans and animals Many doses required, creating issues with compliance and reduced immune response compared to other methods Live attenuated rabies vaccine [2, 14, 18, 19] Contains less virulent form of rabies virus but still capable of replication in host cells Intramuscular injection or oral administration Primarily animals, though still given to humans in some parts of the world Risk of reversion to pathogenic strain and expensive, especially when administered orally Recombinant-vectored vaccine [13, 20-25] Contains attenuated vectors expressing the rabies virus glycoprotein Intramuscular injection or oral administration Animals with human use restricted to clinical trials Expensive to produce; limited studies involving its use in humans TABLE 1: Characteristics, route of administration, target population, and limitations of different types of rabies vaccines
RkJQdWJsaXNoZXIy OTc5MDU=