Aw. Gherardin et al., Early rabies antibody response to intramuscular booster in previously intradermally immunized travelers using human diploid cell rabies vaccine, J TRAVEL M, 8(3), 2001, pp. 122-126
Background: Postexposure treatment (PET) of travelers who may have had a po
tential rabies exposure is simpler, safer, and cheaper if the traveler is p
reimmunized. Preimmunization can be done with human diploid cell rabies vac
cine (HDCV) administered intramuscularly or intradermally. Some authorities
, however, are now advocating that travelers vaccinated by the intradermal
(ID) route should be treated as if they are not immunized. A particular con
cern raised is that travelers who have received pre-exposure rabies vaccina
tion intradermally, may have a delayed response to postexposure boosters. T
his study is designed to elucidate whether a single intramuscular (IM) HDCV
booster will provoke an early (day 5) immune response in individuals given
pre-exposure ID HDCV.
Methods: Twenty-nine travelers who had received a course of three 0.1 mL ID
HDCV between 12 and 24 months previously were given a single 1.0 mL IM boo
ster of HDCV. Rabies antibody levels were compared 5 days later to those be
fore the booster.
Results: Twenty-five of the 29 subjects (86%) showed an adequate rise in vi
rus neutralizing antibody (VNA) titer 5 days after booster. Nine of the 29
subjects (31%) had inadequate antibody levels prior to the simulated postex
posure booster. Five days after the postexposure booster, 27 of 29 (93%) ha
d adequate antibody levels. The other 2 travelers were subsequently shown t
o have adequate VNA levels when tested 4 and 6 weeks later, respectively.
Conclusion: For travelers who were given pre-exposure ID HDCV vaccination w
ithin the last 2 years and received one IM postexposure booster dose of HDC
V, most mounted an adequate early immune response. This data does not suppo
rt a change in current recommendations for rabies PET in this group. Furthe
r research to ascertain the duration of protection of pre-exposure ID rabie
s immunization is required.