Pfizer COVID Shot Has 37 Percent Higher Risk of Mortality Than Moderna Shot - Study | 19 May 2025 | According to a new study, adults who received the Pfizer Comirnaty COVID-19 shot were more likely to die than adults who had the Moderna Spikevax COVID-19 shot. The study looked at 9.2 million adults living in Florida who received either Comirnaty or Spikevax within six weeks, from December 2020 through January 2022. Half of the nearly 1.5 million participants received the Pfizer shot and the other half had the Moderna shot. Participants were matched based on age and gender. The study, "Twelve-Month All-Cause Mortality after Initial COVID-19 Vaccination with Pfizer-BioNTech or mRNA-1273 among Adults Living in Florida," was conducted by Florida Surgeon General, Joseph Ladapo, MD, and Retsef Levi, Ph.D., of the Massachusetts Institute of Technology (MIT), as well as two other researchers. The study is in preprint and has not yet been peer-reviewed.