Intradermal pre-exposure rabies vaccine elicits long lasting immunity

A retrospective cohort study of current rabies antibody titres from adults who received pre-exposure immunisation administered intradermally between 1994 and 2005, examining the decay in titre over time relative to the interval since last dose, and the total dose received. Participants receiving at least 0.6 ml total dose intradermally of vaccine over at least two clinic visits and all with three clinic visits, were shown to have an adequate titre with measurable levels of antibody indicating sero-conversion above 0.5 IU/ml, irrespective of the time interval since the last dose. No clear relationship was found between time interval since immunisation and the level of antibody. Using a schedule that administers 0.6 ml of rabies vaccine over three clinic visits the boosting interval could be extended towards ten years; substantially cheaper than the standard licensed intramuscular dosing schedule.