Immunogenicity and safety of low-dose intradermal rabies vaccination givenduring an Expanded Programme on Immunization session in Viet Nam: results of a comparative randomized trial

The World Health Organization recently recommended a rabies vaccine pre-exp osure schedule using 3 intradermal (ID) injections of one-fifth the standar d intramuscular (IM) dose of current cell culture vaccines as a cost-reduci ng alternative for developing countries. As a strategy to improve further t he acceptability of childhood rabies immunization, we assessed, in a contro lled, randomized trial performed in 240 Vietnamese infants, the possibility of associating ID administration of a one-fifth dose of purified Vero-cell rabies vaccine (PVRV) with routine Expanded Programme on Immunization vacc ines given at 2, 3 and 4 months of age (diphtheria, tetanus, whole-cell per tussis and inactivated poliomyelitis combined vaccine, DTP-IPV). Safety and immunogenicity results were compared with a group of infants given 2 IM do ses of PVRV (2, 4 months) in association with DTP-IPV (2, 3, 4 months). Aft er ID injection, more infants experienced local reactions, particularly red ness, but these reactions were generally mild and transient. The rate of sy stemic reactions was the same in both groups. Although the rabies antibody titres (rapid fluorescent focus inhibition test) were higher 1 month after the third vaccine dose in the IM group (30.6 IU/mL vs 12.0 IU/mL in the ID group), all infants in both groups had achieved WHO-acceptable protective a ntibody titres (greater than or equal to 0.5 IU/mL) at this time. There was no evidence for any interference between DTP-IPV and rabies vaccine, suppo rting the interest of a low-dose ID PVRV pre-exposure regimen in infants li ving in rabies-endemic developing countries.