ABSTRACTIn a recent article, X. Li et al. [mBio 7(1):e02232-15, 2016,http://dx.doi.org/10.1128/mBio.02232-15] investigate the utility of a vaccine composed of theStaphylococcus aureusprotein clumping factor A (ClfA) in protecting mice fromS. aureusinfection. ClfA, one of the first proteins to be identified as a potential vaccine antigen forS. aureusprophylaxis, is currently a component of several investigational vaccines. The authors conclude that ClfA may not be effective forS. aureusprophylaxis. In contrast, previously published papers reporting positive data suggested that ClfA was potentially an important vaccine target to prevent invasiveS. aureusdisease. This commentary addresses the observed differences between the findings of Li et al. and those from other publications, highlighting the importance for preclinical vaccine antigen assessments to reflect the biological role of said antigen in virulence and, consequently, the importance of choosing appropriate preclinical disease models to test such antigens.