Immune response to rabies vaccine in Alaskan dogs: failure to achieve a consistently protective antibody response.

Previous studies in Thailand and Tunisia have shown that one injection of dog pre-exposure rabies vaccine does not produce a lasting antibody titre in a significant group of animals. We therefore duplicated the Thai study in a small North American community using healthy, owned dogs. A tissue culture vaccine of known high antigenicity was given intramuscularly as one primary injection and antibody titres were determined by the rapid fluorescent focus inhibition test on days 14, 30, 60, 180 and 360. Titres were less than 0.5 i.u./mL in 27% of dogs bled at 2 months, 24% at 6 months, and in 33% one year after the primary vaccination. In rabies endemic regions, it may be hazardous to rely on the previous vaccine history of a biting dog when making post-exposure management decisions. A retrospective study of antibody levels in previously vaccinated dogs in North America also indicated that a single injection of vaccine often failed to result in adequate titres.

Immune response to rabies vaccine in Thai dogs: a preliminary report.

Serum neutralizing antibody to rabies virus was determined in previously unvaccinated Thai pet dogs after receiving one subcutaneous dose of inactivated tissue culture rabies vaccine (Rabdomun, Coopers Animal Health Company, Germany, 4.55 IU ml-1 potency). Geometric mean titres on days 14, 30, 60, 180 and 360 were 2.14, 2.30, 0.45, 0.14 and 0.05 IU ml-1, respectively, by the rapid immunofluorescent focus inhibition test. Titres of neutralizing antibody to rabies virus did not correlate with the age of the dog at the time of vaccination or with the presence or absence of anaemia or blood parasites. Six out of 50 (12%), 11 out of 43 (25.6%) and 13 out of 31 (42%) dogs had no detectable rabies antibody in serum 60, 180 and 360 days, respectively, after vaccination. Three of these antibody-negative dogs were given another dose of vaccine. Antibody reappeared on day 14 but rapidly declined within 60 days. These data suggest that one dose of tissue culture vaccine in dogs by the subcutaneous route of injection is not adequate to maintain rabies neutralizing antibody in serum for 1 year.

Rabies in Thailand: 1990.

Of the more than 100,000 courses of postexposure rabies treatment given in Thailand annually, 95% consist of brain tissue-derived vaccine without immune globulin. Rabies tissue culture vaccines and immune globulins are expensive by the standards of developing countries. When they are given according to either of two proven intradermal postexposure schedules, significant savings can be achieved without loss of efficacy. Purified equine rabies immune globulins account for approximately 10% of the cost of human products administered to exposed individuals and have been shown to be safe and effective. A canine preexposure immunogenicity study with a potent, inactivated tissue culture vaccine revealed that 12.5% of Thai dogs failed to develop protective antibody titers 2 months after one subcutaneous injection. Previous studies have shown significant antigenic differences between Thai street rabies virus and European and North African strains.

New purified Vero-cell vaccine prevents rabies in patients bitten by rabid animals.

The protective effect of a new, potentially economical tissue-culture rabies vaccine, purified vero-cell rabies vaccine (PVRV), was tested in 106 patients bitten by animals with proven rabies. 0.5 ml PVRV was given intramuscularly on days 0, 3, 7, 14, 28, and 91; 47 patients with severe exposure were also given 20 IU/kg human rabies immune globulin (HRIG). All patients are alive and well after 1 year. Side-effects of treatment were negligible. Rabies neutralising antibody (greater than or equal to 1.6 IU) was demonstrated on day 14 and persisted for 1 year in every case. There was no significant suppression of the antibody response by HRIG. If the untreated mortality is 15%, PVRV is 81% efficient in protecting patients against rabies encephalitis (95% confidence limit). PVRV is likely to replace human diploid-cell strain vaccine as the most widely used tissue-culture rabies vaccine.