Rubella antibodies in Australian immunoglobulin products

Rubella antibodies are not routinely measured in immunoglobulin products and there is a lack of information on the titer in Australian products. To facilitate future studies of the effectiveness of passive immunisation for preventing rubella and congenital rubella syndrome, this study measured the concentration of rubella-specific antibodies in Australian intramuscular (IM) and intravenous (IV) human immunoglobulin products suitable for post-exposure prophylaxis using a chemiluminescent immunoassay. The GMT ± GSD for the IM product was 19 ± 1.2 IU/mg (2980 ± 1.2 IU/mL). The GMT ± GSD for the IV product was 12 ± 1.5 IU/mg (729 ± 1.5 IU/mL). At present, Australian guidelines recommend offering non-immune pregnant women exposed to rubella 20 mL of intramuscular immunoglobulin within 72 hours of exposure. This equates to 42,160 IU of rubella antibodies if the lowest titer obtained for the Australian IM product is considered. The same dose would be delivered by 176 mL of the Australian IV product at the lowest measured rubella-specific antibody titer.