Children's shorter stature, fearlessness of animals and inability to protect themselves place them at high risk of rabies, particularly in endemic countries with poor control of animal rabies. Therefore in 1995, we undertook a clinical trial in Ho Chi Minh City, Vietnam to evaluate the safety and immunogenicity of rabies vaccine given pre-exposure, in association with combined DTPer (whole-cell)-IPV.

After written informed consent by parents or guardians, 83 healthy Vietnamese infants aged 2 to 5 months, were randomised to receive either a single intramuscular (im) dose of DTP-IPV (group A) at weeks 0, 5, 10 (3 doses), or 3 doses of DTP-IPV in association with an im dose of Purified Vero Cell Rabies Vaccine (PVRV: 8.4 IU/dose; group B) at weeks 0 and 10 (2 doses). Titres for D, T, Per, Polio and Rabies were assayed at weeks 0 (pre) and 15(post).

No severe clinically significant adverse reactions were reported in either group. At week 15, 100% of infants, irrespective of the group, achieved seroprotection thresholds defined as follows: D,T ≥ 0.01 IU/mL; Per:≥1/40; Polio I, II, III: ≥1/5. However a significant decrease in D titres reaching 0.1IU/ml was observed in group B: 90% vs 100% in group A. Post-RFFIT rabies titres were high, i.e. 20.1 IU/mL (100% ≥0.5 IU/mL) vs<0.05 IU/mL in group A. These results show the good immunogenicity of 2 im doses of PVRV in infants, but suggest some interference with other common EPI antigens which must be studied further.