One remarkable aspect of the Covid-19 pandemic has been how often unpopular scientific ideas, from the lab-leak theory to the efficacy of masks, were initially dismissed, even ridiculed, only to resurface later. Another reversal in thinking may be imminent. Some scientists have raised concerns that the safety risks of Covid-19 vaccines have been underestimated. But the politics of vaccination has relegated their concerns to the outskirts of scientific thinking. The Vaccine Adverse Event Reporting System, or Vaers ... is a database that allows Americans to document adverse events that occur after receiving a vaccine. Vaers data for Covid-19 vaccines shows an interesting pattern. Among the 310 million Covid-19 vaccines administered, several adverse events are reported at high rates in the days immediately following vaccination, then drop sharply thereafter. The silence around these potential signals of harm reflects the policy surrounding Covid-19 vaccines. The stigma of such concerns is bad for scientific integrity and could harm patients. Four serious adverse events follow this arc, according to data directly from Vaers: low platelet count (thrombocytopenia); non-infectious myocarditis or inflammation of the heart, especially in those under 30; deep vein thrombosis. The implication is that the risks of a Covid-19 vaccine may outweigh the benefits for some low-risk populations, such as children, young adults, and people who have recovered from Covid-19.