Suppressant effect of human or equine rabies immunoglobulins on the immunogenicity of post-exposure rabies vaccination under the 2-1-1 regimen: a field trial in Indonesia. MAS054 Clinical Investigator Group.

WHO's reference protocol for post-exposure rabies vaccination advises five intramuscular injections on days 0, 3, 7, 14, and 30; in addition, rabies immunoglobulins (RIG) must be given to serious cases of exposure (grade III severity). Some studies indicate that these immunoglobulins suppress the immunogenicity of rabies vaccine when administered according to an alternative protocol of four injections (2-1-1) on days 0, 7, and 21, which was therefore not recommended for grade III exposures. To test this effect, we conducted a multicentre study in Indonesia using three groups of subjects. One group received only the Vero-cell rabies vaccine (PVRV, Verorab, usual commercial lot) according to the 2-1-1 schedule. The second and third groups received the same schedule of PVRV, plus either equine rabies immunoglobulins (ERIG, 40 IU/kg body weight) or human rabies immunoglobulins (HRIG, 20 IU/kg body weight). Our results confirmed the immunoglobulin suppressant effect, which was more pronounced with human than equine immunoglobulins. In both groups receiving immunoglobulins, the seroconversion rates did not reach 100% on day 28 and the geometric mean antibody titre was lower. Thus, WHO's recommendation in 1992 of the reference protocol plus immunoglobulins for severe cases is substantiated by these results in Indonesian subjects. If the 2-1-1 regimen is chosen by the treating physician and immunoglobulins are indicated, preference should be given to purified equine RIG, which also costs less than human RIG.