A 2-dose single-visit intradermal postexposure prophylaxis (PEP) vaccine schedule was as immunologically effective and safe as a 4-dose single-visit intradermal PEP for rabies in healthy adults 7 to 28 months after 2-dose single-visit intradermal pre-exposure prophylaxis (PrEP). The results of the clinical trial (trial registered with EU Clinical Trials Register: EudraCT 2014-00183612) were published in Clinical Infectious Diseases.

In this comparative trial, 303 healthy adults received 2 intradermal doses of 0.1 mL purified chicken embryo cell vaccine in a single visit. After 1 year, these participants were randomly assigned to either 4- or 2-dose booster doses of 0.1 mL purified chicken embryo cell vaccine, again in a single visit.

Participants were evaluated on day 7 following their booster doses and all but one individual per group had an adequate rabies antibody titer >0.5 IU/mL. The geometric mean of the 4-dose and 2-dose groups were 20 IU/mL vs 14 IU/mL, respectively (P =.0228). There were no serious adverse events reported during the trial. Only local mild and transient reactions at the injection site were observed in 14.9% following PrEP and in 49.6% to 53% during PEP.

Study investigators stated that their trial adds further evidence that a single-visit, 2-dose intradermal PrEP can “induce robust anamnestic responses 7 days after additional booster doses.” They added that this schedule, “given only once or possibly repeated without a specific time window, may be appropriate for any type of healthy traveler,” but further research is still required to determine whether it would be immunogenic in more vulnerable travelers or groups of populations as well.

The results led study investigators to conclude that a single-visit 2-dose pre-exposure and postexposure schedule appear to be adequate. Further, they believe that with the reporting of only mild and local side effects, this schedule should be more convenient for travels.

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Reference

Soentjens P, De Koninck K, Tsoumanis A, et al. A comparative immunogenicity and safety trial of two different schedules of single-visit intradermal rabies post-exposure vaccination following a single-visit pre-exposure vaccination [published online December 19, 2018]. Clin Infect Dis. doi: 10.1093/cid/ciy983