When to Get the Rabies Vaccine

Series of Injections to Prevent or Avert an Infection

Man preparing vaccine
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Rabies is not the public health concern that it once was but is still very much in the consciousness of those who live near wildlife, particularly in areas where there are large populations of raccoons, bats, skunks, or foxes.

Rabies is caused by a class of virus known as the lyssavirus, of which there are numerous animal-specific strains. The virus is transmitted primarily through an animal bite and can cause serious and even life-threatening illness if left untreated.

For those considered to be at high risk of exposure, a rabies vaccine is available. It not only provides blanket protection against the disease but can be used to avert an infection if delivered before symptoms appear.

Rate of Infections Worldwide

Due to improved wildlife control measures and routine pet vaccinations, rabies among humans is rare. In fact, according to the Centers for Disease Control and Prevention, only around 55 cases have been reported in the United States since 1995.

The same cannot be said in other parts of the world where rabies is seen to be endemic. These include parts of Asia and Central Africa where more than 55,000 rabies-related deaths occur each year. China and the Democratic Republic of Congo represent the bulk of these deaths.

In the United States, bat bites are by far the most common route of animal-to-human transmission followed by bites from rabies-infected dogs.

The states with the highest rate of animal rabies are Texas, Virginia, Pennsylvania, New York, Maryland, New Jersey, Georgia, and California.

Symptoms of Rabies

When a person is bitten, scratched, or gets infected body fluids into the eyes, nose, mouth, or broken skin (often by handling dead, diseased animals), the virus will travel through the peripheral central system (the nerves the branch from the spinal cord and brain) and gradually makes its way to the central nervous system (the spinal cord and brain).

During the early stages of the disease, there may be few, if any, symptoms other than a non-specific fever or headaches. On average, the incubation period (the time between exposure and symptoms) is between one and three months.

As the infection progresses and makes its way toward the brain, symptoms of encephalitis (inflammation of the brain) and meningitis (inflammation of the tissues surrounding the brain and spinal column) will develop. At this prodromal stage of infection, a person may experience a severe and often dramatic range of physical and neuropsychiatric symptoms including:

  • Dizziness
  • Fatigue
  • Loss of appetite
  • Nausea and vomiting
  • Sensitivity to light
  • Excessive salivation
  • Anxiety and agitation
  • Confusion
  • Paranoia
  • Abnormal behavior (including aggression and bouts of terror)
  • Hallucination
  • Difficulty swallowing
  • Hydrophobia (fear of water)
  • Seizures
  • Partial paralysis

From this point, the disease can rapidly progress, leading to delirium, coma, and eventually death. Once a person exhibits symptoms of the disease, treatment is almost never effective, and the likelihood of mortality is over 99 percent.

About the Rabies Vaccine

The rabies vaccine is made with an inactivated (“fully killed”) virus that cannot cause infection.

There are two types used for the prevention of vaccine:

  • Imovax (human diploid cell vaccine)
  • RabAvert (purified chicken embryo cell vaccine)

Both are delivered by injection into the muscle of the upper arm over three doses. After the initial shot, the second shot is given seven days later, and the third is given 14 to 21 days after that.

Side effects are typically mild and tend to resolve on their own within a day or so. They include injection site swelling and pain, muscle aches, dizziness, headaches, and nausea.

In rare instances, a person may experience a hypersensitive reaction, including a potentially life-threatening, all-body allergic response known as anaphylaxis.

If experiencing any symptoms of rash, breathing difficulties, heart palpitation, vomiting, fainting, or swelling of the tongue or face, call 911 or go to your nearest emergency room.

For this reason, RabAvert should be avoided and substituted with Imovax in anyone who has a known allergy to either chicken or chicken eggs.

Generally speaking, a healthy, vaccinated individual should enjoy 10 years of immune protection. For those at high risk of rabies exposure, booster shots can be given every six months to two years, as needed.

Vaccination After Exposure

In addition to preventing rabies, the rabies vaccine can be used to avert an infection after a person has been bitten or come into high-risk contact with a rabid animal.

Referred to as post-exposure prophylaxis (PEP), it involves the use of human immune globulin (Igg), a type of medication made from healthy human blood which has a high concentration of defensive immune cells (called antibodies). These are used either with or without Imovax or RabAvert.

The two Igg medications approved for this purpose are:

  • Imogam Rabies-HT (human rabies immune globulin)
  • HyperRab TM S/D (human rabies immune globulin)

If a person is bitten by a rabid animal, the PEP procedure would involve the cleansing of the wound with soap and water and/or irrigation with a virucidal (virus-killing) solution. The course of treatment would vary by the individual’s vaccination history:

  • If the person has not been vaccinated for rabies previously, he or she would receive multiple injections of Igg in and around the wound to saturate the area with rabies antibodies. That would be accompanied by a series of four shots of either Imovax or RabAvert (delivered on the same day and followed by additional shots three, seven, and 14 days later).
  • If a person has been previously vaccinated, Igg is not needed. Instead, a two-shot series of Imovax or RabAvert can be used, one delivered immediately and another given three days later.

Persons who are immune compromised, such as those with advanced HIV infection may require an additional Imovax or RabAvert injection.

Given the grave nature of a rabies infection, there is no contraindication for PEP treatment, including pregnancy.

Who Should Get Vaccinated

Despite the rarity of human rabies in the United States, the fear associated with the disease has resulted in anywhere from 16,000 to 39,000 people being vaccinated each year. Most are those at high risk of exposure, including veterinarians, animal handlers, and wildlife officers as well as spelunkers who are more likely to encounter rabid bats.

The Department of Health and Human Services currently recommends rabies vaccination for:

  • Persons whose activities bring them into frequent contact with either the rabies virus or possibly rabid animals.
  • International travelers who are likely to come into contact with animals in parts of the world where rabies is common.

Sources:

Centers for Disease Control and Prevention (CDC). "Rabies VIS." Atlanta, Georgia: updated October 6, 2009.

CDC. "Rabies: Wound Care – Human Rabies Immune Globulin." Updated March 23, 2016.

Department of Health and Human Services. "Rabies." Washington, D.C.; updated November 2012.

Meseret, B.; Cleaton, J.; Monroe, B. et al. "Rabies surveillance in the United States during 2015." J Amer Vet Med Assoc. 2017; 250(10):1117-30. DOI: 10.2460/javma.250.10.1117.

World Health Organization. (2013) Frequently Asked Questions on Rabies. Geneva, Switzerland: World Health Organization Regional Office for South-East Asia; publication SEA-CD-278.