The effects of uncertainties in published proton fluence spectra for large solar particle events (SPE) on organ dose estimates are largely unknown since uncertainties in the measured spectra are unknown. In this work, input spectra for several large SPEs are adjusted by as much as 50% to account for the spectrum uncertainties. The BRYNTRN space radiation transport code and CAM human geometry model are used to perform the calculations. The calculations are made assuming three organ doses and four nominal thicknesses of spacecraft aluminum shielding. Discussions of dose variations for several events based on different spectrum uncertainty values are presented.