evidence: COVID-19 Vaccine Safety — What We Know - The Pfizer and Moderna vaccines are strongly recommended as safe and effective at preventing serious illness or death from COVID-19. [...] - Roughly 12 months of data, including data from tens of thousands of participants in clinical trials, show that the vaccines are safe and effective at preventing serious disease or death due to COVID-19. [...] - Careful testing. All vaccines go through clinical trials to test safety and effectiveness. For the COVID-19 vaccine, the FDA set high safety standards for vaccine developers to meet. This graphic from the National Institutes of Health shows the four phases a vaccine goes through before it is released to the public.