Rabies post-exposure prophylactic vaccination for returning travelers to Japan

Area of Science:

• Immunology
• Vaccinology
• Public Health

Background:

• Japan's rabies post-exposure prophylaxis (PEP) regimen involves 6 subcutaneous doses, differing from international standards of 4-5 intramuscular doses.
• This study aimed to assess the immunogenicity of the Japanese 6-dose subcutaneous PEP regimen.

Purpose of the Study:

• To evaluate the immunogenicity of a 6-dose subcutaneous rabies post-exposure prophylaxis (PEP) regimen using purified chick embryo-cultured rabies vaccine Kaketsuken (PCEC-K).
• To determine if this regimen aligns with international recommendations for rabies prevention.

Main Methods:

• A prospective, single-center, cross-sectional study involving patients receiving PCEC-K for rabies PEP.
• Exclusion of patients with prior pre-exposure prophylaxis or rabies immunoglobulin use.
• Measurement of rabies virus-neutralizing antibody titers at multiple time points, including after doses 1-4, and the fifth and sixth doses.

Main Results:

• Seroprotection rates (≥0.5 IU/mL) were 90.7% at day 30 and 75.7% at day 90 among 43 participants.
• A significant proportion (85.3%) of patients experienced decreasing antibody titers between days 30 and 90, even after a fifth dose.
• Delayed initiation of PEP (within 48 hours) was noted in 32 patients.

Conclusions:

• The 6-dose subcutaneous administration of PCEC-K induced insufficient seroprotection rates at days 30 and 90.
• The current Japanese PEP regimen may not provide adequate rabies prevention compared to international guidelines.
• Further research into optimized rabies vaccination schedules is warranted.