Human rabies immunoglobulin (HRIG), sometimes referred to as Rabies Immune Globulin (RabIg), is a shot that is given as soon as possible after a likely exposure to rabies. It contains rabies antibodies that immediately inactivate and control the rabies virus until the vaccine begins to work.
Vaccination against rabies is used in two distinct situations:
- To protect those who are at risk of exposure to rabies, i.e. preexposure vaccination;
- To prevent the development of clinical rabies after exposure has occurred, usually following the bite of an animal suspected of having rabies, i.e. post-exposure prophylaxis.
The vaccines used for pre-exposure and post-exposure vaccination are the same, but the immunization schedule differs. Rabies immunoglobulin is used only for post-exposure prophylaxis. Modern vaccines of cell-culture or embryonated-egg origin are safer and more effective than the older vaccines, which were produced in brain tissue.
These modern rabies vaccines are now available in major urban centres of most countries of the developing world. Rabies immunoglobulin, on the other hand, is in short supply worldwide and may not be available, even in major urban centres, in many dog rabies-infected countries
- HRIG is given only one time, at the beginning of treatment for rabies exposure.
- The full dose of HRIG is injected into the exposure wound and into the area around the wound. Any remaining dose of HRIG will be injected into a different muscle from the one where the vaccine shot will be given.
- HRIG is given only to people who have not received the rabies vaccine before their most recent exposure. People who previously received the vaccine already have some rabies antibodies, and another HRIG injection can make the post-exposure vaccination series less effective.
- HRIG may cause pain at the site of the shot and a low-grade fever after the shot is given.
Special warnings and precautions for use
Ensure that Human Rabies Immunoglobulin is not administered into a blood vessel, because of the risk of shock.
True hypersensitivity reactions are rare.
Human rabies immunoglobulin contains a small quantity of IgA. Individuals who are deficient in IgA have the potential for developing IgA antibodies and may have anaphylactic reactions after administration of blood components containing IgA.
Rarely, human rabies immunoglobulin can induce a fall in blood pressure with anaphylactic reaction, even in patients who have tolerated previous treatment with human immunoglobulin.
Suspicion of allergic or anaphylactic type reactions requires immediate discontinuation of the injection. In case of shock, standard medical treatment for shock should be implemented.
Standard measures to prevent infections resulting from the use of medicinal products prepared from human blood or plasma include selection of donors, screening of individual donations and plasma pools for specific markers of infection and the inclusion of effective manufacturing steps for the inactivation/removal of viruses. Despite this, when medicinal products prepared from human blood or plasma are administered, the possibility of transmitting infective agents cannot be totally excluded. This also applies to unknown or emerging viruses and other pathogens.
The measures taken are considered effective for enveloped viruses such as human immunodeficiency virus (HIV), hepatitis B virus (HBV) and hepatitis C virus (HCV) and for the non-enveloped hepatitis A and parvovirus B19 viruses.
There is reassuring clinical experience regarding the lack of hepatitis A or parvovirus B19 transmission with immunoglobulins and it is also assumed that the antibody content makes an important contribution to the viral safety.
It is strongly recommended that every time that Human Rabies Immunoglobulin is administered to a patient, the name and batch number of the product are recorded in order to maintain a link between the patient and the batch of the product.
What is the difference between rabies vaccine and HRIG?
A course of rabies vaccines (given into the shoulder muscle) works to develop long term immunity, but this may take seven days to begin providing protection. For this reason, HRIG is usually given into the wound or site of injury to provide immediate short term protection while the rabies vaccines start to work. Long term protection is essential as rabies infection can take a long time to develop. Not everyone potentially exposed to rabies or ABLV will be advised to have HRIG.
For example, HRIG is generally not required for people who have been previously vaccinated against rabies. When recommended, it is important to have the HRIG as well as the vaccine to ensure complete protection against rabies or ABLV.
What is the difference between ERIG and HRIG?
ERIG is equine RIG and is produced in horses. HRIG is human RIG and is produced in humans.
Both products contain antibodies specifically made against rabies virus. Both products are produced by vaccinating horses (ERIG) or humans (HRIG) and harvesting their plasma which contains antibodies against rabies virus. The dose of ERIG is twice as high (40 IU/Kg of body weight) as the dose needed if you receive HRIG (20 IU/Kg of body weight). Modern (more purified) ERIG is now considered as safe as HRIG by WHO.
How many doses of rabies vaccine are needed following a bite or scratch by a potentially infected animal?
A course of four doses is generally needed over a period of one month (0, 3, 7, 14 days). However, an additional fifth dose is needed at 30 days for anyone who has a weakened immune system. The injections are given in the muscle of the upper arm.
Are there any side effects?
All medicines and vaccines have side effects. For this vaccine, about 20% of people complain of redness at the injection site or a sore arm. Other side effects include fever (8%), headache (5%), stomach upset (5%), muscle aches and pains (5%) and a rash (5%).
A very small minority of people (1 in 10,000) can suffer a severe allergic reaction, with symptoms that might include difficulty breathing and swelling of the throat. This is exactly the same reaction that occurs in some people who are allergic to bee stings or peanuts. Your doctor will ask you to stay in the clinic for about 20 minutes after the rabies vaccination to ensure you are not one of those very few people who are allergic to the rabies vaccine. If this reaction occurs, it is usually easily treated at the clinic.
Throughout the world, five cases of inflammation of the brain have been reported among the millions of people who have been given rabies vaccine. These cases have not been linked with certainty to the vaccine.
Should the vaccinations be stopped if there are side effects?
The disease caused by rabies and ABLV is lethal and the recommended vaccination schedule should be continued unless there is a severe allergic reaction. If a severe allergic reaction occurs, specialist advice should be sought and the risk of developing infection must be carefully considered before deciding to discontinue the vaccinations.
Are there any people who should not have the vaccine for medical reasons?
No. The disease caused by rabies and ABLV infection is lethal, so all people bitten or scratched by a potentially infected animal should have the vaccine. If your doctor thinks there is a risk of a severe allergic reaction, then specialist advice should be sought.
What about women who are pregnant or breast feeding?
There is no evidence that the vaccine can harm unborn babies. Follow up of 200 pregnant women in Thailand found that the vaccine was safe. It is not known if the vaccine is secreted in human milk, but any vaccine present in breast milk should not have harmful effects.
What should you do if you experience vaccine side effects?
For mild side effects such as headache, muscle soreness or fever, paracetamol may be taken every four hours up to a maximum for adults of eight 500 mg tablets in 24 hours. If fever persists or you are concerned about your condition consult your doctor.
When and where is human rabies immunoglobulin (HRIG) given?
When recommended, HRIG is usually given with the first dose of the vaccine. It provides immunity until the vaccine starts to protect at about day 7. It is preferable that as much as possible of the HRIG is injected in and around the wound site.
How is HRIG prepared?
It is prepared from the plasma of donated human blood.
Are there any side effects of HRIG?
Pain and discomfort can occur at the injection site. Fever and chills sometimes occur. As with all medicines, acute severe allergic reactions occur very rarely. Because HRIG is prepared from human blood, the risk of transmitting blood-borne infections cannot be absolutely excluded. This risk also applies to as yet unknown diseases.
The risk of spreading known diseases is reduced during the production of HRIG by screening blood donors, by screening all donated blood for HIV, hepatitis B and hepatitis C, and by further processing of the blood to extract the immunoglobulins. There have been no reports in Australia of transmission of any blood borne disease in people who have received HRIG.
Are there any other adverse effects of HRIG?
Administration of immunoglobulin may interfere with the effectiveness of some vaccines (eg. measles, mumps, rubella and chickenpox vaccines). You should tell your doctor if you have had one of these vaccinations in the two weeks before the HRIG injection.
It may be necessary for you to be re-vaccinated (with measles, mumps, rubella or chickenpox vaccines) four months after the dose of HRIG.
Author : Tina
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