To measure how well a vaccine works in a clinical trial, the Food and Drug Administration (FDA) first looks at the number of people who fell ill with the disease.
The FDA has authorized the use of Pfizer-BioNTech's vaccine for children 12 years and older. FDA’s authorization was based on data showing the vaccine is safe and effective in this age group. Pfizer-BioNTech's vaccine has been through extremely tough safety tests, which includes…
The right to require Covid-19 vaccination in places of business, entertainment, and education ultimately depends on state or local law. So be sure to check requirements specific to your area.
Although rare, some people have reported allergic reactions to the vaccines. An extraordinarily tiny fraction of vaccine recipients have experienced anaphylaxis -- a severe allergic reaction that can impair people's breathing.
The Centers for Disease Control and Prevention (CDC) recommends waiting 14 days after receiving another vaccine to get the Covid-19 vaccine. Similarly, the CDC recommends waiting 14 days after receiving the Covid-19 vaccine to get another vaccine.
People with certain underlying or pre-existing conditions, including cancer, diabetes, kidney disease, obesity, and heart disease, are more likely to experience severe complications from Covid-19 -- so they're strongly encouraged to get the vaccine.
The authorized vaccines do not contain the Covid-19 virus, and you cannot develop Covid-19 from the vaccines. Therefore, the vaccines cannot make you contagious with Covid-19 to anyone you come into contact with.
The Food and Drug Administration (FDA) has granted Emergency Use Authorization (EUA) to the Pfizer-BioNTech vaccine, the Moderna vaccine, and the Johnson & Johnson vaccine. Additional vaccines are in Phase 3 of clinical trials and maybe submitting data for review with the FDA soon. 
Reports of life-threatening reactions resulting from the side effects of Pfizer-BioNTech, Moderna, and Johnson & Johnson vaccines are extremely rare. Still, it's important to address any concerns people may have.
Patient safety is central to the research and development of a vaccine. Like all new medicines or treatments, vaccines must pass a rigorous set of tests before being approved by independent, scientific experts at the U.S. Food and Drug Administration.