Thousands of Americans believe they experienced rare but serious side effects. But confirming a link is a difficult task.Thousands of Americans believe they experienced rare but serious side effects. But confirming a link is a difficult task.Read Moreyour-feed-science, Vaccination and Immunization, Disease Rates, Drugs (Pharmaceuticals), Coronavirus (2019-nCoV), Content Type: Service, Medicine and Health, BioNTech SE, Johnson & Johnson, Pfizer IncNYT > Health