Rabies Vaccine

What is Rabies?

Rabies is an infectious disease caused by a virus and affects the central nervous system. It is often fatal in humans once clinical symptoms start to show1. The virus is normally transmitted in humans through animal bites, but 99% cases are due to domestic dog bites or scratches1.

In India, over 20,000 rabies deaths occur each year, representing one-third of global human rabies2. Children under the age of 15 in rural or urban slums are victims of such dog bites in majority of cases2.

A person infected with Rabies virus will have fever with pain and an unexplained pricking/tingling sensation around the wound/dog bite3. As the virus slowly spreads to the central nervous system, it causes brain and spinal cord inflammation which ultimately leads to death.

There are two forms of Rabies disease viz Furious Rabies and Paralytic Rabies3

  1. Furious Rabies – In this type, patient may become extremely hyperactive or may show excitable behaviour. The infected person may have Hydrophobia (fear of water), sometimes Aerophobia (fear of fresh air). Within a few days of the bite, the infected person may die due to loss of heart functioning.
  2. Paralytic Rabies – this takes place in almost 30% of the cases. The course of duration of this type is longer than Furious Rabies and symptoms are less dramatic. Muscles slowly start to get paralysed, starting at the site of bite/scratch. In due course, Coma starts to develop eventually leading to death. Since, this type of Rabies is often misdiagnosed; it is a heavily under-reported disease.

How is Rabies spread?

Asia and Africa have reported most number of cases worldwide of Rabies deaths in humans1. Other animals that can spread Rabies in humans are Bats (often in America), Foxes, Racoons, Mongoose and other wild carnivore animals. Human to human transmission of rabies is theoretically possible; however it has never been reported.

Where is Rabies found?

Rabies is present in all the continents of the world (except Antarctica) with 95% deaths occurring in Asia and Africa.

In India, Rabies is often reported from rural and urban slums where awareness on animal bites is low.1

What is a Rabies Vaccine?

A Rabies vaccine is a medicine given to prevent rabies disease in humans. It is used under two distinct situations4

  • Pre-exposure Vaccination –

The type of vaccine used for this type is a Modern cell-culture or embryonated-egg vaccine consisting of three full intramuscular (i.m.) doses given on days 0, 7 and 21 or 28. A booster dose is normally not advised in people who have received a full set of pre-exposure vaccination dose. However, in case of an animal bite, 2 booster doses should be received (one on the day of bite, other post 3 days).

  • Post-exposure prophylaxis –

The World Health Organization strictly recommends a set of guidelines for post-exposure prophylaxis of rabies disease (after a person has been exposed to rabies infection) in countries where risk of rabies is high.

Depending on the type of contact with the animal the following procedure should be followed –

  1. a) Wound Healing – Thoroughly cleaning the wound with soap and water followed by application of iodine or povidone.
  2. b) Passive immunization - Human rabies immunoglobulin (HRIG) or equine rabies immunoglobulin (ERIG) or F(ab’)2 products are used in cases of animal bites/scratches/licks on open wound.
  3. c) Active immunization – Cell-culture- or embryonated-egg-based rabies vaccines should always be used for post-exposure prophylaxis.

Who should get vaccinated?

Although Rabies vaccine is not an essential vaccine for most people, it is recommended that people living in high risk areas get vaccinated. Children from rural or urban slums where an animal bite from rabid animals is quite common should get vaccinated.

People who work closely with animals such as Vets, Animal Handlers, Health care personnel/volunteers, wildlife officers, travellers with extreme outdoor exposure should consider Rabies vaccination.

What is the schedule for Rabies Vaccine4?

  1. Pre-exposure rabies vaccination

Pre-exposure rabies vaccination consists of three full intramuscular (i.m.) doses of the vaccine given on days 0, 7 and 21 or 28.

  1. Post-exposure prophylaxis - active immunization

It is given either though intramuscular (i.m.) route or intra-dermal (i.d.).

Intradermal regimens: Intradermal administration of the rabies vaccines has been successfully used in many developing countries that cannot afford the five- or four-dose i.m. schedules. One injection is given intradermally on 2 sites on days 0, 3, 7 and 28.

Are there any side effects4?

Modern Rabies vaccines are well tolerated with very less side effects. These include local pain, swelling and severe itching. Occasionally, restlessness, generalized body pain and headaches have been noted after intramuscular or intradermal injections.

References

  1. Ann Med Health Sci Res. 2016 Mar-Apr; 6(2): 115–119. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4866364/
  2. Proc Natl Acad Sci U S A. 2016 Dec 20; 113(51): 14574–14581. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5187709/
  3. http://www.who.int/mediacentre/factsheets/fs099/en/
  4. http://www.who.int/ith/vaccines/rabies/en/