Revision of the Thai Red Cross intradermal rabies post-exposure regimen by eliminating the 90-day booster injection.

The Thai Red Cross intradermal post-exposure rabies prophylaxis regimen (TRC-ID) is being used in Thailand, the Philippines, Sri Lanka and is making inroads in India. It consists of two injections of 0.1 mL of any World Health Organization recommended tissue culture rabies vaccine intradermally at two sites on days 0, 3, 7, followed by one injection on days 28 and 90. Two decades of experience had shown that approximately 11% of 187,000 possibly rabies exposed subjects who received the TRC-ID schedule, did not return for the 90-day booster. No rabies deaths had, however, been reported from this group. This stimulated two studies to determine whether the 90-day booster can be abolished. They demonstrated that, if the single 28-day 0.1 mL injection is increased to two at two sites, a comparable antibody response can be achieved and the 90-day booster can be omitted. The tissue culture rabies vaccine used in the preliminary study was purified chick embryo vaccine (PCEC Chiron) and for this study it was chromatography purified Vero cell vaccine (CPRV, Aventis-Pasteur). CPRV had been previously shown to be as immunogenic and effective as purified Vero cell rabies vaccine (PVRV).

Prospective immunogenicity study of multiple intradermal injections of rabies vaccine in an effort to obtain an early immune response without the use of immunoglobulin.

The present study sought to determine whether increasing and accelerating rabies vaccine administration would result in earlier protective levels of neutralizing antibody. Results indicated that the 8-site and double-dose Thai Red Cross intradermal regimens produced higher antibody titers by day 14 but not significantly higher titers by days 5 and 7. Administration of rabies immunoglobulin into and around bite wounds on the first day of rabies prophylaxis should remain the optimal postexposure treatment.

Post-exposure rabies treatment in pigs.

A rabid dog invaded a Thai pig farm and severely mauled 11 adult pigs. This offered an opportunity to study efficacy of a human type post-exposure vaccine regimen with and without rabies immunoglobulin. A commercial veterinary tissue culture rabies vaccine and equine rabies immune globulin were used. All pigs survived for 1 year following the exposure. All animals developed detectable rabies neutralizing antibodies on day 7 and levels over 0.5IU/ml on day 14. This small study suggests that post-exposure rabies treatment using a proven human regimen, applied to valuable farm animals, can be safe and effective.

Use of rabies vaccines after reconstitution and storage.

Storing freshly reconstituted purified chick embryo rabies vaccine at 4 degrees C for 1 week allowed use of <1 ampoule of 1.0 mL for 1 patient for day 0, 3, and 7 immunizations, representing considerable savings in vaccine and also possibly allowing use of this cost-saving regimen in centers that see <1 rabies-exposed patient daily. The 90-day booster dose mandated in the current intradermal regimen may not be necessary if the day 28 dose is doubled, eliminating 1 clinic visit at no additional cost in vaccine.