Anti-rabies serum — also called Rabies Immunoglobulin (RIG) — provides immediate passive immunity at the site of a rabies exposure. It is administered alongside the first dose of the anti-rabies vaccine (ARV) on Day 0 for all Category III bites in previously unvaccinated individuals. Two types are available in India: ERIG (Equine Rabies Immunoglobulin, 40 IU/kg) and HRIG (Human Rabies Immunoglobulin, 20 IU/kg).
How to Calculate Anti-Rabies Serum Dose
The anti-rabies serum dose is calculated strictly by body weight. Use the formula below and the calculator above to get the exact dose and vial count.
ERIG Dose Formula (Equine Rabies Immunoglobulin)
ERIG dose (IU) = Body weight (kg) × 40 IU/kg
Volume (ml) = Dose (IU) ÷ 300 IU/ml | Vials (5 ml) = Round up (Dose ÷ 1,500)
Worked example — 68 kg patient:
ERIG dose = 68 × 40 = 2,720 IU
Volume to draw = 2,720 ÷ 300 = 9.07 ml
Vials needed (5 ml / 1,500 IU each) = ceil(2,720 ÷ 1,500) = 2 vials
Draw 9.07 ml total (use both vials; discard remaining 0.93 ml from vial 2)
HRIG Dose Formula (Human Rabies Immunoglobulin)
HRIG dose (IU) = Body weight (kg) × 20 IU/kg
Volume (ml) = Dose (IU) ÷ 150 IU/ml | Vials (2 ml / 300 IU) = Round up (Dose ÷ 300)
Worked example — 55 kg patient:
HRIG dose = 55 × 20 = 1,100 IU
Volume to draw = 1,100 ÷ 150 = 7.33 ml
Vials needed (2 ml / 300 IU each, Berirab-P) = ceil(1,100 ÷ 300) = 4 vials
ERIG vs HRIG — Comparison Table
| Feature |
ERIG (Equine) |
HRIG (Human) |
| Dose |
40 IU/kg body weight |
20 IU/kg body weight |
| Concentration |
300 IU/ml (Indian standard) |
150 IU/ml (Berirab-P, Imogam) |
| Vial sizes |
5 ml (1,500 IU), 10 ml (3,000 IU) |
2 ml (300 IU) — Berirab-P |
| Skin test |
Mandatory before administration |
Not required |
| Origin |
Hyperimmune horse plasma |
Hyperimmune human plasma |
| Half-life |
~7 days |
~21 days |
| Side effects |
Anaphylaxis, serum sickness possible |
Minimal (homologous origin) |
| Indian manufacturers |
CRI Kasauli, Vins Bioproducts, Premium Serums |
Imported (CSL Behring Germany via Bharat Serums) |
| Availability |
Free in govt. rabies centres |
Private hospitals, expensive (₹2,000–₹5,000/vial) |
ERIG Skin Sensitivity Test — Step-by-Step Protocol
A skin sensitivity test is mandatory before administering ERIG. Never skip this step — anaphylaxis can occur even with the test dose.
Before you begin: Keep an anaphylaxis kit ready — Inj. Adrenaline 1:1000 (0.5 ml IM), Inj. Hydrocortisone 100 mg IV, Inj. Pheniramine 45 mg IV, IV fluids, oxygen. The patient should not be on an empty stomach. Conduct the test in a hospital or clinic setting with the patient seated.
1
Dilute ERIG 1:10 in sterile water for injection (WFI). Prepare 0.1 ml of this diluted ERIG for the test dose.
2
Inject 0.1 ml of the 1:10 diluted ERIG intradermally on the flexor surface of one forearm to raise a small wheal (3–4 mm diameter).
3
As a negative control, inject an equal volume of sterile WFI intradermally on the flexor surface of the other forearm.
4
Read at 15 minutes. A wheal >10 mm with surrounding erythema (flare), when the control is negative, is a positive test.
5
If negative: Proceed with ERIG administration. If positive: Switch to HRIG. If HRIG unavailable, desensitize and administer ERIG under close medical supervision with anaphylaxis protocol in place.
Note: Anaphylactic reactions can occur even if the skin test is negative, and even during the test dose itself. Always have the patient observed for 30 minutes after ERIG administration. Serum sickness (Type III reaction) can develop 7–10 days after ERIG; symptoms include urticaria, arthralgia, and fever.
How to Administer RIG — Wound Infiltration Protocol
Correct administration technique maximises the protective effect of anti-rabies serum at the viral entry point.
1
Wound toilet first: Wash the wound with soap and running water for at least 15 minutes, then apply povidone-iodine. This step alone significantly reduces the rabies virus load.
2
Draw up the calculated dose of ERIG or HRIG. Use a 23G or 25G needle for wound infiltration.
3
Infiltrate as much of the dose as anatomically feasible into and around the bite wound — at wound margins, wound base, and surrounding tissue. Inject in multiple small-volume aliquots. Do not inject into the wound as a single bolus.
4
If the wound is small and cannot absorb the full calculated volume, dilute the remaining RIG in sterile normal saline to a sufficient volume and infiltrate all around the wound.
5
Any remaining RIG after wound infiltration should be injected intramuscularly at a site distant from the vaccine injection. Vaccine and RIG must never be given at the same site.
6
Administer the first dose of anti-rabies vaccine (ARV) at the same visit — in the opposite arm deltoid. Proceed with the standard Day 0, 3, 7, 28 schedule.
Critical rule: RIG must be administered on Day 0 only — alongside the first vaccine dose. If missed on Day 0, it can still be given up to Day 7. After Day 7, RIG is not indicated as an active vaccine-induced antibody response is presumed. Never repeat or re-dose RIG at a later visit — this can block the active immune response.
When Is Anti-Rabies Serum (RIG) Indicated?
RIG is not needed for every animal bite. Use the bite category classification (NCDC India / WHO) to decide:
| Category |
Type of Exposure |
RIG Needed? |
ARV Needed? |
| Category I |
Touching/feeding animals, licks on intact skin |
No |
No |
| Category II |
Nibbling uncovered skin, minor scratches/abrasions, no bleeding |
No* |
Yes |
| Category III |
Deep bites with bleeding, multiple bites, head/neck/hand bites, licks on mucosa/broken skin, bat exposure |
Yes |
Yes |
*For immunocompromised patients (HIV, transplant, on steroids/immunosuppressants), RIG is indicated for Category II exposures as well.
Related Rabies PEP Calculators
DS
Reviewed by Dr. Sharma
MBBS, AFIH · Medical Officer, AAC Clinic Punjab ·
Experience in emergency medicine, industrial health & addiction medicine. Background in anti-rabies vaccine management at primary care level.
Frequently Asked Questions — Anti-Rabies Serum Dose
What is the dose of anti-rabies serum (ERIG) per kg body weight in India?
The standard dose of ERIG (Equine Rabies Immunoglobulin / anti-rabies serum) is 40 IU per kg body weight as per NCDC India 2019 and WHO guidelines. For a 60 kg patient, the total ERIG dose is 2,400 IU. The generally accepted maximum is 3,000 IU (10 ml of standard 300 IU/ml ERIG). Use the calculator above to get the exact dose for any body weight.
What is the dose of HRIG (Human Rabies Immunoglobulin) per kg?
HRIG dose is 20 IU per kg body weight — half the dose of ERIG. This is because HRIG has a longer half-life (21 days vs ~7 days for ERIG) and is of homologous human origin. For a 60 kg patient, HRIG = 1,200 IU. Berirab-P (CSL Behring) — the most common HRIG in India — comes in 2 ml vials of 150 IU/ml (300 IU per vial). HRIG does not require a skin sensitivity test.
How many vials of anti-rabies serum are needed for a given weight?
For ERIG at standard Indian concentration (300 IU/ml): a 5 ml vial contains 1,500 IU; a 10 ml vial contains 3,000 IU. Divide the calculated dose by 1,500 and round up to find 5 ml vials needed. Example: 70 kg × 40 = 2,800 IU → 2 vials of 5 ml (3,000 IU available; draw 9.33 ml). For HRIG (Berirab-P, 150 IU/ml): each 2 ml vial = 300 IU. Divide dose by 300 and round up.
Does ERIG require a skin sensitivity test before administration?
Yes, skin testing is mandatory before ERIG. Inject 0.1 ml of 1:10 diluted ERIG intradermally on one forearm. Use sterile water for injection as a negative control on the other arm. Read at 15 minutes. A wheal >10 mm with flare is positive — switch to HRIG. If HRIG unavailable, desensitize and administer ERIG in a hospital setting with full anaphylaxis protocol. HRIG requires no skin test.
Can anti-rabies serum be given after Day 7 of the vaccine course?
No. RIG (ERIG or HRIG) must ideally be given on Day 0 alongside the first rabies vaccine dose. If missed initially, it can still be administered up to Day 7. Beyond Day 7, an active vaccine-induced antibody response is presumed to have begun and RIG is no longer indicated — giving it at that stage may actually interfere with the immune response. Never give RIG as a repeat dose at a later visit.
What is the difference between ERIG and HRIG?
ERIG (Equine RIG): derived from horse plasma, dose 40 IU/kg, requires skin test, may cause allergic reactions (anaphylaxis, serum sickness 7–10 days later), available domestically from CRI Kasauli and other Indian manufacturers, stocked free at government rabies treatment centres. HRIG: from hyperimmune human plasma, dose 20 IU/kg, no skin test required, minimal side effects, imported (Berirab-P, Imogam), expensive (₹2,000–₹5,000/vial), not routinely available in government facilities. Both provide equivalent passive immunity when administered correctly around the wound.
How should ERIG or HRIG be administered into the wound?
Infiltrate as much of the calculated dose as anatomically feasible into and around the bite wound on Day 0. Use a 23G or 25G needle and inject in multiple small-volume aliquots at the wound margins, wound base, and surrounding tissue — never as a single bolus. If the wound cannot absorb the full volume, dilute RIG in sterile normal saline and infiltrate. Any remaining RIG after wound infiltration should be injected intramuscularly at a site distant from the vaccine injection site. Vaccine and RIG must never be given at the same anatomical site.
Is anti-rabies serum (RIG) needed for all dog bites in India?
No. RIG is indicated only for Category III bites in previously unvaccinated individuals. Category III includes: deep puncture wounds, bites with bleeding, multiple bites, bites on head/neck/face/hands/genitals, licks on mucous membranes or broken skin, and bat exposures. For immunocompromised patients, RIG is also indicated for Category II exposures as well. Category I (touching, feeding, licks on intact skin) needs no treatment; Category II (minor scratches, no bleeding, in immunocompetent patients) needs vaccine only, not RIG.
Is anti-rabies serum free in government hospitals in India?
ERIG is available free of cost at government rabies treatment centres, district hospitals, CHCs, and medical colleges under the National Rabies Control Programme. HRIG is imported and expensive (₹800–₹1,500 per 2 ml vial) and is not routinely available in government facilities. Private hospitals charge approximately ₹500–₹1,200 per 5 ml vial of ERIG. If ERIG is unavailable at a local facility, contact the nearest Anti-Rabies Centre or CRI Kasauli, Himachal Pradesh for emergency supply guidance.
Should RIG be given to a patient who was vaccinated against rabies previously?
No. Previously vaccinated individuals who have completed a full rabies vaccination course with a potent cell culture vaccine do not require RIG. They need only 2 booster vaccine doses on Day 0 and Day 3. Giving RIG to a previously vaccinated person is not indicated and may interfere with the anamnestic (memory) immune response generated by the booster doses.