Immunogenicity of a modified intradermal pre-exposure rabies vaccination schedule using a purified chick embryo cell vaccine: An observational study

Background In Australia, recommendations for pre-exposure rabies vaccination involve 3 doses of vaccines on days 0, 7, and 28 using either 1.0 mL intramuscular (IM) vaccines, or 0.1 mL intradermal (ID) vaccines. The use of IM vaccines is limited by their prohibitive cost, and ID vaccines by the recommendation for serology 2-3 weeks post-vaccination. A recent study reported the successful use of human diploid cell rabies vaccines (HDCV) with a modified ID schedule (2 × 0.1 mL ID on days 0 and 7) - Travellers Rabies Intradermal 2 site (TRID2) - that was affordable, required less time to complete than standard ID schedules, and achieved a seroconversion rate of 94.5%. This study reports the immunogenicity of pre-exposure rabies vaccination using a purified chick embryo cell vaccine (PCECV) with the TRID2 schedule. Method Travellers aged 10-50 years were given the PCECV using the TRID2 schedule, and serology was performed at day 28. Results Fifty-four travellers were vaccinated, with a seroconversion rate of 94.4% at day 28. Seroconversion rates did not differ between age groups, but older travellers had lower antibody levels. Conclusions This study supports the effectiveness of the TRID2 schedule, and found the schedule equally effective with HDCV or PCECV.