Following the release of data from phase III trials on 9 November, vaccine makers Pfizer and BioNTech deployed their vaccines under emergency-use rules. The developer of another leading vaccine, Moderna, did the same.
When a vaccine is granted emergency approval, and the vaccine is rushed through, companies might not have enough data to establish long-term outcomes, such as safety. The trial phases for a vaccine typically last for multiple years to establish if the vaccine is truly safe.
This did not happen.
From Johnson & Johnson:
Phase 1 testing marks the first time the vaccine is tested in a small group of adults, usually between 20 to 80 people, to evaluate its safety and measure the immune response it generates.
Phase 2a studies aim to determine the most effective dose, and expand the safety experience with the vaccine.
Researchers look for expected reactions to the vaccine—which could include anticipated adverse events, like headache, muscle pain, redness and swelling at the injection site or low-grade fevers—as well as serious adverse events.
Phase 1 and 2a clinical trials normally last several months to even a year before proceeding to Phase 2b or Phase 3 trials, in which the pool of people receiving the vaccine increases. Companies combined Phase 1 and Phase 2 trials for its investigational SARS-CoV-2 vaccine into one phase, known as Phase 1/2a. Many experts urged against the combination of trials or rushing the vaccine.
Phase 3 is a stage of the clinical trial where even more volunteers receive the vaccine to study whether it's actually effective. Phase 3 trials usually take multiple years.
Phase 4:After a successful Phase 3 trial, vaccine manufacturers submit an application to regulatory bodies such as the European Commission or the U.S. Food and Drug Administration (FDA). At this stage, clinical trial data is reviewed to make sure the vaccine is safe and effective.