The U.S. Food and Drug Administration (FDA) issued an Emergency Use Authorization (EUA) for Moderna's COVID-19 vaccine, as expected after a government-mandated independent panel recommended its approval earlier this week. This is the second vaccine after the Pfizer that is now EUA approved in the US -BioNTech vaccine was approved last week.
According to Dr. Anthony Fauci, speaking in a new interview on NBC's Today show, the Moderna vaccine could be given to Americans "Monday or Tuesday". This is in line with the deadlines between the Pfizer EEA and the first patients who actually received the vaccine last week.
Like Pfizer's vaccine, Modernas is an mRNA therapy. That means it doesn't contain an actual virus – just genetic instructions that tell a person's body to make a specific protein. This protein is more or less identical to the one that SARS-CoV-2, the virus that causes COVID-19, uses to attach to a host's cells and replicate. Moderna's vaccine causes a person to make only the protein that is harmless on its own, and then their natural defenses through their immune system react to it and develop a method to fight it off. This defense system is “remembered” by the body, while even after a short period of time the vaccine naturally breaks down, leaving a person with immunity, but nothing else.
The Oxford AstraZeneca The vaccine, which is not yet approved for use in the US, uses a weakened and modified cold virus that does not spread in humans to produce the spike protein in recipients, causing the body to generate its own immune response generated. This is a well-established method of making a vaccine, but both Moderna and Pfizer's mRNA therapies have proven very effective in preliminary data from their large Phase 3 clinical trials.