Booster effect of a new chromatographically purified Vero-cell rabies vaccine (CPRV): immunogenicity and safety of a single or double injection

Immunogenicity and safety of WHO-approved TRC-ID regimen with a chromatographically purified Vero cell rabies vaccine with or without rabies immunoglobulin in children

INTRODUCTION

Children are at risk of rabies exposure in many Asian countries. The safety and immunogenicity profile of the WHO-approved two-site intradermal Thai Red Cross regimen (modified TRC-ID regimen; 2-2-2-0-2) with a new chromatographically purified Vero-cell rabies vaccine (CPRV) is lacking. Area covered: We studied the safety and immunogenicity of the TRC-ID regimen with a new CPRV in non-immunized Thai children with possible or proven rabies exposure. Thirty-nine seronegative patients (age range 2-14 years) with rabies exposure (WHO categories II or III) received two 0.1-mL intradermal doses of CPRV at both deltoid regions on days 0, 3, 7, and 28. Twenty-five patients (64.1%) received rabies immunoglobulin due to having rabies exposure, according to WHO category III. All serum samples were tested for rabies neutralizing antibody (Nab) by the rapid fluorescent focus inhibition test (RFFIT) before vaccination, and on days 14 and 90 after vaccination. All patients had an adequate immune response (Nab titers ≥ 0.5 IU/mL) on days 14 and 90. No patients died of rabies infection. No serious adverse reactions were observed. Expert commentary: CPRV is economic, safe, and immunogenic if given as the modified TRC-ID regimen in children.

Immunogenicity and booster efficacy of pre-exposure rabies vaccination

A multivariate analysis was used to identify factors influencing the immunogenicity of rabies vaccine and to assess the efficacy of booster injections in a cohort of 407 people monitored prospectively for 10 years after primary vaccination. Rabies vaccine (HDCV or PVRV) was injected by intramuscular route either on days 0 and 28 or on days 0, 7 and 28. All the participants received a booster injection on day 365. At the end of follow-up (year 10), 163 subjects had titers >0.5IU/ml (group A) and 59 subjects had titers <0.5IU/ml (group B: poor responders). The number of injections had a significant influence (P<0.001) on the magnitude of the serological response to rabies vaccine, but the type of vaccine and the potency of the batches did not (P=0.07 and P=0.06, respectively). The difference between GMTs on day 365 and day 379 was significantly lower in group B than in group A (13 and 50.70IU/ml, respectively; P<0.001). In conclusion, our study confirms that the rabies pre-exposure vaccination protocol of three intramuscular injections significantly decreases the proportion of poor responders at 10 years. Moreover, our findings indicate that a routine booster injection at 1 year could significantly increase the levels and duration of antibody titers.