The Immunogenicity of a Modified Intradermal Pre‐exposure Rabies Vaccination Schedule—A Case Series of 420 Travelers

Abstract

Current Australian recommendations for rabies pre-exposure vaccination involve the use of cell-culture-based rabies vaccines, which are administered via intramuscular (IM) or intradermal (ID) routes. ID vaccination is more affordable for travelers, but is only recommended if there is sufficient time to perform serology 2 to 3 weeks post-vaccination and confirm immunity prior to travel. We report the immunogenicity of a modified ID schedule that can be completed in less time than the standard ID schedule, and allow more travelers to be vaccinated prior to departure. Travelers were offered a modified schedule if they were unable to afford standard IM vaccinations, and did not have time to complete a standard ID course. The modified schedule consisted of two ID injections of 0.1 mL of human diploid cell rabies vaccine administered on days 0 and 7, and serology was performed to determine immune status at a time between day 21 and 28. A total of 420 travelers aged between 10 and 65 years were vaccinated using the modified ID course. The overall seroconversion rate was 94.5%, with 397 travelers developing antibody levels of >0.5 IU/mL when tested at approximately 21 days post-vaccination. The modified ID schedule used in this case series was highly effective, had similar immunogenicity to the standard ID schedule, and should be considered in travelers who are unable to complete standard IM or standard ID courses of rabies vaccines.