Abridged Rabies-Exposure Regimen Appears Effective

By David Douglas

October 18, 2019

NEW YORK (Reuters Health) - In people bitten by rabid dogs, intradermal rabies vaccinations given over the course of a week may provide the same protection as a standard four-session, one-month post-exposure prophylaxis, according to an observational study.

"These findings contributed to the change in 2018 WHO recommendations for rabies post-exposure prophylaxis," Dr. Arnaud Tarantola of Institut Pasteur du Cambodge, in Phnom Penh, Cambodia, and colleagues write in The Lancet Infectious Diseases, online September 27.

The month-long Thai Red Cross regimen has been used successfully for decades, the team notes. However, an abridged approach would improve access and reduce direct and indirect costs. Several studies have suggested the safety of such measures.

To investigate further the researchers studied 116 people bitten by dogs with laboratory-confirmed rabies and 20 controls bitten by rabies-negative dogs between 2016 and 2018. Per the Thai Red Cross regimen, all received two intradermal injections of post-exposure prophylaxis on days 0, 3, 7, and 28. These were given with or without equine rabies immunoglobulin as per 2010 WHO recommendations.

Serum samples were obtained for detection of rabies virus neutralizing antibodies on days 0, 7, 28, and 42. On day 28, before the last injection, all had reached rabies-virus-neutralizing-antibody titres at or beyond 0.5 IU/mL, considered to be protective,

Further examination of those in the rabies group showed that the median level was 1.08 IU/mL on day 7; on day 28, it had reached 26.86 IU/mL and on day 42, 26.74 IU/mL. The fourth session thus provides no additional benefit.

There were no deaths in either group after one year and therefore, the researchers conclude, "rabies post-exposure prophylaxis can be abridged to a three-session (on days 0, 3, and 7) . . . to improve vaccine coverage at no risk to patients."

This study, they add, "is complemented by a retrospective study on clinical outcome after at least 6 months, which found no significant difference in survival among patients who received three versus four intradermal post-exposure prophylaxis sessions."

Dr. Charles E. Rupprecht, co-author of an accompanying editorial, told Reuters Health by email that the study "adds significantly to our confidence base towards the global elimination of human rabies caused by dogs."

Dr. Rupprecht of Lyssa LLC, a research company in Atlanta, concluded, "Such important clinical work demonstrates the great dose-sparing utility of the intradermal route for vaccine application over a one-week period, which can be life-saving in human rabies post-exposure prophylaxis, where cost, availability, timeliness and patient compliance are critical factors to avoid this acute, progressive, fatal viral encephalitis."

Dr. Tarantola did not provide comments in time for publication.

SOURCE: https://bit.ly/2IGbF44 and https://bit.ly/329lf7g

Lancet Infect Dis 2019.