COVID-19 vaccines are on the fast-track to approval. How will we know they're safe?

In June, the FDA issued guidelines for the approval of COVID-19 vaccines. In those guidelines, the agency described what safety evaluations a vaccine would need to pass and noted that a vaccine should show at least 50% efficacy in clinical trials, meaning that under perfect conditions, people who get the vaccine would be at least half as less likely to be infected with the coronavirus compared with unvaccinated people.   LiveScience