Your Questions :

  1. Is there any Anti-Rabies Vaccine which gives life long immunity against Rabies ? In the case of immunization against Tetanus, persons who are immunized properly do not require boosters on repeat exposures. Why should persons previously immunized against rabies require boosters on repeat exposures?

       Question asked by Dr. D. Chattopadhyay, Barasat, West Bengal.

There are no Anti-Rabies Vaccines, tissue culture or any other type which confers life long immunity against rabies. The TCVs currently used are only being used for about two decades at the most. Human life is not so short. WHO Technical Report Series 931 is available on the web. Some portions of it are printed in this issue of this journal for the benefit of doctors who are not familiar with the internet. As per that report persons who have received 5 doses of TCVs in “ESSEN” schedule, of a vial of the vaccine IM over deltoid on Days 0, 3, 7, 14 and 28 and those persons who have received pre-exposure schedule of TCV, one vial IM on Days 0, 7 and 21 or 28, and have seroconverted, will require only two doses of TCV, one each on Day 0 and on Day 3, in case of a repeat exposure. This holds good for all TCVs having a potency of 2.5 i.u./ vial. This is irrespective of the time since the Primary course of vaccination, provided the patient had seroconverted after the primary course of vaccination. Most healthy persons have no problems with it. In the case of persons who are immunocompromised due to disease or taking of medicines the rabies virus neutralizing antibodies (VNA) titres should be tested at least 15 days after completion of the primary course of vaccination. Persons known to be immuno-compromised should in the event of a secondary exposure receive full course of vaccination against rabies including RIGs. In those cases where there is a doubt on the ability of a person’s immune system to launch an anamnestic response effectively, the VNA titre should be checked after the two booster doses for confirmation. Patients do not come to doctors with a label attached on their health status. Doctors have to anticipate the condition and sometimes choose the lesser evil. Rabies is a dangerous disease with almost hundred percent fatality. There are no second chances. It is always safer to err on the higher side than on the lesser side. The presently available TCVs are very safe in the prescribed doses.

  1. What should be the Pre or Post-exposure vaccination regimen for immunodeficient individuals ? Do they require double dose of vaccine on Day 0 only ?

        Question asked by Dr. A. K. Gupta, of Delhi.

There is no possibility of immunodeficient persons taking pre-exposure vaccination against rabies because of the uncertain status of the immune response elicited at the time of primary immunization or subsequent secondary immunization when required.

Post-exposure vaccination is an emergency and a life saving procedure. It cannot be denied to anyone requiring it. Immunodeficient persons when exposed to rabies should have a very thorough wound washing with soap or detergents, RIGs infiltration of the wounds even in category II exposures, immediate administration of TCVs in “ESSEN” schedule of five IM shots. The use of ID regimens have been discouraged by WHO TRS 931 report in such type of cases.

Some authors recommend the use of double dose of TCV by IM route on Day 0 only for hastening the immunization process. Some other authors believe that increasing the antigen load excessively will not hasten the the immune response because there is a capacity beyond which the immune system will not respond. In Immunodeficient persons the possibility of the immune system not responding to excessive dose of the antigen exists.