Rabies vaccine.

Abstract

Although human rabies is rare in the United States, wildlife rabies has been increasing. This uniformly fatal disease continues to be a worldwide public health threat. Acute infection causes rapidly progressive neurologic impairment, including anxiety, dysphagia, and seizures. Virus is transmitted in humans primarily through animal exposure; the incubation period ranges from 5 days to several years (average, 4 to 6 wk). Prevention and treatment of those exposed to rabies are key.Indications for use of the rabies vaccine include pre-exposure prophylaxis for those at high risk (such as veterinarians) and postexposure prophylaxis. Possible exposures to rabies should be evaluated individually,and consultation with local public health officials may be necessary. Factors influencing the need for antirabies treatment include type of exposure, animal rabies epidemiology, and circumstances of the incident. Transmission occurs only if the virus penetrates through open cuts or wounds in skin or mucous membranes. Bite exposures are most common. Possible nonbite exposures include large amounts of aerosolized virus (bat caves),organ (cornea) transplants from rabies victims, and scratches by rabid animals.Rabies should be considered in all exposures to wild carnivores and bats. In the United States, skunks, raccoons, and bats are the animals infected most often; foxes, coyotes, cattle, dogs, and cats are other possible sources. In 1997 there were four cases of human rabies in the United States. Since 1980, more than 50% of United States cases have been associated with bat variants of the virus. Bats can transmit rabies through minor bites. Thus, bat contact with humans or pets should be avoided. Bites from rodents and lagomorphs (including rabbits) rarely require antirabies treatment.An unprovoked attack is more likely to indicate that an animal is rabid than an exposure during feeding or handling of an animal. Fully vaccinated animals rarely become infected. Suspect domestic animals should be captured and observed by a veterinarian for 10 days. If signs of rabies develop, the animal should be killed and examined. Wild animals and bats should be killed at once. If results of fluorescent antibody examination of the brain are negative, the exposed person need not be treated.The combination of local wound care and passive and active vaccination is highly effective in the prevention of rabies. Immediate and thorough washing of bites or nonbite exposures with soap and water prevents virus from entering neural tissue. Concomitant use of human rabies immune globulin (RIG) and vaccination are recommended unless a patient has been vaccinated previously. RIG (20 IU/kg) should be administered, with as much of the full dose as possible infiltrated into and around the wound(s) and the rest administered intramuscularly at a distant site. Postexposure prophylaxis with RIG bridges the time between start of treatment and vaccine induction of antibody. RIG and vaccine should be administered in different syringes in different parts of the body.Three vaccines are available in the United States: Human diploid-cell rabies vaccine (HDCV), rabies vaccine adsorbed (RVA), and purified chick embryo cell culture (PCEC). All should be administered intramuscularly(1.0 mL) in the deltoid region for adults and in the anterolateral zone of the thigh for young children, with repeat doses on days 3, 7, 14, and 28. Although previous duck embryo vaccines were painful and dangerous, current vaccines are safer. Side effects are rare in children, but may include local reactions such as pain, erythema, swelling, or itching at the injection site or mild systemic reactions such as nausea, headache, abdominal pain, myalgia,and dizziness. Serum sickness-like reactions and anaphylaxis have occurred rarely. Neurologic abnormalities after the administration of HDCV occur in approximately 1 in 150,000 doses. Fortunately, vaccine failures are extremely rare.