This type of vaccine, using messenger RNA, has never been approved in the U.S. before.
Doctors said mRNA sends a message to the body to create what are called spike proteins. Those proteins are found on the outside of novel coronavirus cells. Once your body forms spike proteins, it triggers an immune response, so if you ever come in contact with the real COVID-19, your body will already have the antibodies to fight it off.
Pfizer’s mRNA vaccine contains no live virus, so experts say you can't get COVID-19 from the shot.
Moderna’s vaccine also uses mRNA. The pharmaceutical company is also seeking emergency use authorization from the FDA.
Early results from Pfizer and Moderna’s clinical trials have shown their vaccines are 95% effective in preventing symptoms of COVID-19.
What we don’t know is how long that immunity lasts.
Although Pfizer and Moderna are the furthest along in their clinical trials, there are more than 300 vaccine candidates being worked on all over the world. A total of 11 are in clinical trials in the U.S.