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‘Less can be more’: Shorter rabies PrEP schedule safe, effective

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June 30, 2018

In healthy participants, intradermal administration of a double dose of rabies pre-exposure prophylaxis, or PrEP, given during two clinic visits was safe and noninferior to a standard three-visit schedule, according to recent data.

Given the efficacy of the shortened schedule, which may result in wider acceptance, Patrick Soentjens, MD, PhD, head of the travel clinic at Queen Astrid Military Hospital’s center for infectious diseases in Brussels, and colleagues said intradermal (ID) administration of a two-dose, two-visit PrEP regimen is now one of the first-line schedules recommended by the Strategic Advisory Group of Experts on Immunization for international travelers and individuals at risk for rabies in endemic countries.

“Rabies represents an unremitting and neglected global challenge. As such, new shortened ID schedules aim to be cost-, dose- and time-sparing, while maintaining safety and effectiveness,” the researchers wrote in Clinical Infectious Diseases. “Shortened PrEP ID schedules, using simpler low-dose vaccine regimens, can be considered an illustration that less can be more.”

Soentjens and colleagues examined the safety and efficacy of the shortened PrEP schedule in participants recruited from the Belgian Armed Forces. Five hundred participants were randomly assigned to receive two 0.1-mL doses of the HDCV rabies vaccine (Sanofi) intradermally at baseline and day 7 (2ID group) or a single 0.1-mL dose of HDCV intradermally at baseline, day 7 and day 28 (3ID group). One to three years after primary vaccination, all participants received a single booster dose of HDCV. The injection was intended to mimic a situation in which PrEP is administered following rabies exposure. The primary endpoint was the percentage of participants with an adequate anamnestic rabies antibody response (>0.5 IU/mL) 7 days after the booster dose.

Overall, 211 participants in the 2ID group and 200 participants in the 3ID group completed the primary vaccination and booster regimens. All participants in both groups had a sufficient rabies antibody response greater than 0.5 IU/mL on day 7 after the booster injection, according to the researchers. The average geometric mean titer was 37 IU/mL in the 2ID group vs. 25 IU/mL in the 3ID group.

One adverse event occurred in the 3ID group during primary vaccination, and two adverse events occurred in the 2ID group after booster vaccination. Local irritation at the injection sites was mild and transient, the researchers reported. The proportion of participants with vaccine-related discomfort was low and did not significantly differ between the 3ID and 2ID groups (14.5% vs. 11.6%).

“Data from the present study substantiates the safety and the immunogenicity of the 2ID regimen for rabies immunization in adult healthy travelers,” Soentjens and colleagues concluded. “Whether this schedule is safe and effective in children in [low-income countries] still needs to be explored.” – by Stephanie Viguers

Disclosures: One author reports receiving grants from the Bill and Melinda Gates Foundation and vaccine manufacturers for research outside of the submitted work. Soentjens reports no relevant financial disclosures.

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