Endotoxin in vaccines has long been recognized as a cause of adverse events and is generally regarded as a contaminant. However there are now a number of vaccine candidates that contain endotoxin as either antigen or adjuvant, particularly vaccines for Neisseria meningitidis based on native outer membrane vesicles (NOMV). Vaccines containing meningococcal endotoxin are not new. From 1907 to 1939 approximately 400,000 individuals were immunized with whole cell vaccines against meningococcus. We reviewed reports of meningococcal vaccinations from this period to characterize the adverse events to draw a baseline for evaluating meningococcal NOMV vaccines. The majority of these investigators conclude that whole cell vaccination was well tolerated with an adverse event profile comparable to other whole cell vaccines for Gram negative pathogens. There is insufficient data to draw conclusions on the duration of protection, if any, induced by whole cell meningococcal vaccines.