All the things you need to know about the Pfizer, the Moderna, Johnson & Johnson COVID-19 vaccines
The J&J vaccine uses a harmless virus — an adenovirus, not a coronavirus — to ferry instructions, in the form of DNA, to your cells.
These instructions, train your immune system to recognize proteins that stud the surface of the coronavirus and to create antibodies and immune cells that can fight off the virus if you ever become infected.
The Pfizer and Moderna vaccines uses a microscopic bubble of grease to carry instructions to your cells in the form of something called messenger RNA.
The two mRNA vaccines (Pfizer's and Moderna's) each require two doses, spaced three to four weeks apart. The J&J vaccine is just one shot. In all cases, it takes time for your body to make sufficient antibodies — so a person is considered "fully vaccinated" and protected from COVID-19 only after at least two weeks since the final shot.
Right now, only the Pfizer vaccine is authorized for use in people as young as 12 to 17 years old. The FDA is reviewing data from Moderna's studies in younger people right now, and it's likely that Moderna shots will become available to teens soon, too.