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

Abstract

The World Health Organization recently recommended a rabies vaccine pre-exposure schedule using 3 intradermal (i.d.) injections of one-fifth the standard intramuscular (i.m.) dose of current cell culture vaccines as a cost-reducing alternative for developing countries. As a strategy to improve further the acceptability of childhood rabies immunization, we assessed, in a controlled, randomized trial performed in 240 Vietnamese infants, the possibility of associating i.d. administration of a one-fifth dose of purified Vero-cell rabies vaccine (PVRV) with routine Expanded Programme on Immunization vaccines given at 2, 3 and 4 months of age (diphtheria, tetanus, whole-cell pertussis and inactivated poliomyelitis combined vaccine, DTP-IPV). Safety and immunogenicity results were compared with a group of infants given 2 i.m. doses of PVRV (2, 4 months) in association with DTP-IPV (2, 3, 4 months). After i.d. injection, more infants experienced local reactions, particularly redness, but these reactions were generally mild and transient. The rate of systemic 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 i.m. group (30.6 IU/mL vs 12.0 IU/mL in the i.d. group), all infants in both groups had achieved WHO-acceptable protective antibody titres (> or = 0.5 IU/mL) at this time. There was no evidence for any interference between DTP-IPV and rabies vaccine, supporting the interest of a low-dose i.d. PVRV pre-exposure regimen in infants living in rabies-endemic developing countries.