The accurate measurement of biologically and clinically relevant functional antibodies, induced following immunization with sexual stage/mosquito (SSM) antigens, remains critical for decision-making. The assay of choice for making these determinations continues to be the standard membrane-feeding assay (SMFA). The SMFA is a complex functional assay that assesses the capacity of antibodies to inhibit the development of oocysts in the mosquito and thus reduce the mosquito’s ability to transmit malaria parasites to humans. While an initial qualification of the SMFA was completed in 2012 at MVI’s SMFA reference center, the assay remains inherently variable and efforts continue to better control this variability and to make improvements to the assay.