The first COVID-19 vaccine that’s likely to go into any American arms is Pfizer’s mRNA vaccine, which was designed and developed by the German biotech company BioNTech. Here, we give a rundown of basic facts about the vaccine and an overview of how it works.

Vaccine name: BNT162b2; Design type: mRNA; Dose number: 2, 21 days apart

Efficacy: 95% efficacy in preventing symptomatic COVID-19 in adults without prior evidence of infection a week or more after receipt of the second dose.

Safety: No serious safety concerns reported. The shots, however, routinely elicit a fairly strong temporary reaction in many people that can include injection site pain, fatigue, headache and chills.

Expected dose availability: Worldwide, up to 50 million doses, or enough for approximately 25 million people, by the end of 2020, with up to 1.3 billion doses expected in 2021.

Expected timeline: First doses not available in U.S. until at least a few days after Dec. 10, when an advisory committee is meeting to review the company’s emergency use authorization submission to the Food and Drug Administration.

Operation Warp Speed involvement: No support for the trials or research and development, but the U.S. government inked a $1.95 billion deal in July as part of OWS to buy 100 million doses, with the potential to acquire up to 500 million more, assuming the vaccine is authorized.

Storage considerations: -70°C (-94°F) for long-term storage; after thawing, vaccine vials can be stored at refrigerator temperatures for up to five days.