Pfizer’s vaccine received full FDA approval for ages 16 and up on August 19, 2021. Moderna’s vaccine received full FDA approval for ages 18 and up on January 31, 2022.
The development was more rapid than many other vaccines. But, it used the same process of Phase 1 and Phase 2 trials following appropriate safety measures. Phase 3 trials were large-scale trials done rigorously with very clear outcome definitions.
The safety measures and approaches taken during COVID-19 vaccine trials were the same as those used in trials to approve other vaccines. No steps were skipped, but some steps were conducted on an overlapping schedule to gather data faster than usual.
The main difference between Emergency Use Authorization versus full FDA approval is that emergency testing needs two months of monitoring rather than six months. When you look at the history of vaccines, if patients were to develop side effects, these occurred within two months. We have now been using these vaccines for more than a year and more than 545 million vaccines have bene safely administered. We have not seen anything that would make us believe that the risks outweigh the benefits.
https://www.bu.edu/articles/2021/myths-vs-facts-covid-19-vaccine/ (Boston University)