IMMUNOGLOBULIN
Vaccines and immunoglobulin’s are used to protect from several fata diseases.
Vaccine provides active immunization where as immunoglobulin’s provide passive immunization.
In this section we will cover few immunoglobulins available.
- Hepatitis-B Immunoglobulin
Hepatitis-B Immunoglobulin (HBIg)
Neonates born to HBsAg positive, and especially HBeAg positive mothers are at the highest risk of getting infected with Hepatitis B and becoming chronic carriers.
There are plenty of examples of Hemophilia, Sickle Cell Anemia, Hodgkins’ Lymphoma, Leukemia, Dialysis, Kidney Transplantation, and now Liver Transplantation patients getting infected with Hepatitis B during treatment.
In a known case of exposure to the Hepatitis B Virus, the patient has an option to simultaneous Passive immunization (Hepatitis B Immune globulin) and Active immunization (Hepatitis B Vaccine) to get protected successfully.
In Newborn babies a dose of 100 IU of HBIg and 0,1, 6 month vaccine schedule was recommended by CDC and IAC internationally. Back home, IAP also recommends the same dose and schedule. This flat 100 IU dose in a neonate amounts to 100 IU/3Kg or 33.3IU/Kg and in a Low Body Weight may mean up to 40 IU/Kg or more.
However, although hepatitis B Immunoglobulin as such may not be contra-indicated in pregnant women, it is not routinely recommended in this group of patients.
Combined Active-passive Immunization For Hepatitis B In Adults, HBIg (0.06 ml/kg) is to be administered to individuals along with 0, 1 & 6 month dose of Hepatitis-B vaccine.
Hepatitis B Immunoglobulin in Liver Transplantation on HBIg 2000 IU (10 mL) daily from days 1 to 20 and then weekly for the first 2 years. After 2 years, all patients received 2000 IU (10 mL) monthly. Calling this as small frequent dosing of HBIg given posttransplant, it did not cause side effects while achieving serum levels >1000 IU/L.
Hepatitis B Infection In Acute Lymphoblastic Leukemia And Lymphoma Patients strategy of Presumed Exposure Prophylaxis with Passive-Active immunization using hepatitis B immunoglobulin (0.06 ml/kg) and vaccine (0, 1 & 6 month ) has been shown to be successful by medical oncologists from India and other developing countries during the last 4 years.
Pediatric patients on dialysis must receive all the IAP recommended vaccines for healthy children, except the oral polio vaccine. Adult patients have been advised to take the hepatitis B vaccine series, pneumococcal vaccine, yearly influenza vaccinations, tetanus diphtheria toxoids, and varicella vaccine, if they are susceptible. Implementation of proper guidelines and initiating vaccination (with Hepatitis B vaccine before putting patient on dialysis) were shown to bring down the infection rate in dialysis patients. The strategy of simultaneous Passive- protective titer may take at least 3-4 months Acti ve immunization should work in the case of dialysis patients as well.
Routine Post Exposure Prophylaxis:
It has been reported that incubation time for hepatitis B is between 45 to 180 days
63 with a mean of 60-90 days. Thus, a cover is needed not only for a short period but it is
necessary to give a cover for long period as well. For Post-exposure prophylaxis in adults, the international norm remains 0.06ml/Kg body weight dose of HBIg. This dose is equivalent to 12 IU/Kg of body weight, which works well in this set of patients, as it is a single exposure, and HBIG is accompanied with simultaneous vaccination.
Such a small dose may not be adequate with higher and/or repeated viral exposure. There are many such studies using very high doses of HBIG successfully in the high- risk patients such as HBsAg and HBeAg positive chronic hepatitis B carrier cirrhotic patients undergoing Liver Transplantation and neonates born to chronic Hepatitis B carrier mothers.
HBIg dose in Liver Transplant Patients:
For example, in Liver Transplant patients, dosages such as 45,000 IU loading dose 64 followed by 5000 monthly , or 2000 IU daily for 20 days followed by weekly to maintain a titer of 1000 IU/L have been 19 used . Others have used somewhat lower doses to maintain an anti-HBs titer of 500 IU/L initially and 150 IU/L 20 later or a higher dose of 10,000 IU 65 monthly . Doses in Liver Transplant patients thus vary in the range of 33 IU/Kg weekly (lowest) to between 80 to 166 IU/Kg monthly (medium) and a high loading dose of 750 IU/Kg in a 60 Kg individual.
HBIg dose in Neonates:
For prevention of perinatal transmission, the infant is being simultaneously vaccinated and not undergoing immunosuppressive therapy. Yet the dose is 100 IU in 0.5 ml. If we consider the average weight of the child as 3 kg, the dose becomes almost 33 IU/Kg. Chances of repeated exposures to high viral load being less, single HBIG dose with full vaccination schedule proved adequate in this setting.
In an underweight baby weighing about 2.5 Kg, the same fixed dose of 100 IU becomes 40 IU/Kg, equivalent to 0.20 ml/Kg. This is the mean value of the recommendations (32 IU to 48
IU/Kg) made by manufacturers and the dose appears to be appropriate for Pediatric patients.
Hepatitis B Immunoglobulin Leukemia/Lymphoma Patients:
The ideal dose should lie between the very high dose used for Liver transplant patients (continuous exposure) and the one used in single exposure prophylaxis.
Thus, a flat 40 IU/Kg dose similar to neonatal dose, but used at repeat monthly intervals for around 5 months along with vaccination in Leukemia/Lymphoma patients could be ideal. Where facilities exist, it is also possible to monitor the titer monthly and take corrective steps accordingly.
Hepatitis B Immunoglobulin in Dialysis Patients:
Dialysis patients respond poorly to vaccination. In addition, higher age and higher creatinine blood levels (4mg/dL) are known to yield poor 71 response to Hepatitis B vaccine with only 37% vaccines producing protective titer of 10 mIU/ml. Thus, the dose of Hepatitis B Immunoglobulin may vary between 12 IU/Kg to 40 IU/Kg for at least 3 monthly doses, or till adequate response to active immunization, depending upon the patient profile, and the risk involved.
Using a formulation of 200 IU/ml, which actually contained 312 IU/ml of anti- 72 HBs , it has been shown that after intramuscular administration, the product has a biological half-life of 23 +/- 5 days, and attains a C max (Geometric Mean) of between 31 to 55% at a median of 5 +/- 3 days. In Liver Transplant patients a very short half-life of 2 to 10 days has been reported.
Since the IV preparations are very expensive, Hepatitis B Immunoglobulin preparations for intramuscular administration are preferred. However, as they are required to be given in a high dose, it is desirable to have a product of high Specific Activity.