Minimum Acceptable Rabies Antibody Titer Level
A correlate of protection for rabies antibody titers has not been defined. The minimum antibody level historically recommended by ACIP is one that results in complete neutralization of rabies virus at a 1:5 serum dilution by the rapid fluorescent focus inhibition test. This is approximately equivalent to a titer of 0.1–0.3 IU/mL. Stakeholders have advocated for a specific titer value in IU/mL units of measure (rather than a range) and, ideally, one that aligns with current global guidance (i.e., that of the World Health Organization). Although no infections among vaccinated persons occurred with the previous ACIP cut-off titer, most published studies use 0.5 IU/mL as a correlate of protection. This level is now endorsed by ACIP and replaces the previous minimum acceptable rabies antibody titer. The higher value provides a more conservative limit for indicating inadequate response to rabies vaccination and the need for booster doses.
Morbidity and Mortality Weekly Report. 2022;71(18):619-627. © 2022 Centers for Disease Control and Prevention (CDC)