OBJECTIVE: This study evaluated the safety and potency of a new highly purified equine rabies immunoglobulin (ERIG) through indirect measurement of suppression of vaccine-induced antibody production using rapid fluorescent focus inhibition test.
METHODOLOGY: This is a prospective, randomized open labeled clinical study on healthy volunteers. Forty-five subjects were randomly assigned to three groups of 15 subjects: All groups received the purified chick embryo cell culture (PCEC) rabies vaccine using the Zagreb regimen (2-1-1). Group A then received ERIG at the same site where the PCEC vaccine was administered; Group B received ERIG at a distant site from where the PCEC vaccine was administered; Group C received only the PCEC vaccine at the same regimen. Arithmetic mean (AM), standard deviation (SD) and range were used to describe the baseline characteristics. Geometric mean titer (GMT) was calculated on Days 0, 7, 14, 21 and 28. Wilcoxon rank-sum test and Kruskall-Wallis Analysis of Variance test were used to compare the means of two and three groups, respectively. Local and systemic adverse reactions were reported by subjects and monitored by investigators.
RESULTS: By day 14, 64% of the subjects in Group A, 20% in Group B and 7.0% in Group C failed to seroconvert. During that same period, comparative analysis of GMT of Group A (0.36, 95% CI: -17.92 to 18.64), Group B (1.09, 95% CI: 0.14 to 2.04) and Group C (3.90, 95% CI: -0.63 to 8.43) showed statistically significant differences (p = 0.0016). In terms of safety, neither serious adverse events nor anaphylactic reactions were reported.
CONCLUSION: ERIG is a potent and safe product that can be effectively used for passive immunization in category III rabies exposures. In resource-limited areas, this product is an excellent alternative to human rabies immunoglobulin (HRIG).