Moderna’s coronavirus vaccine is on its way to the states after being officially approved for use in the general public under an emergency use authorization.

The Food and Drug Administration announced its approval late Friday, and roughly six million doses of the Moderna drug began shipping from warehouses on Sunday, Operation Warp Speed officials said. Pfizer’s vaccine received similar authorization seven days earlier, and was administered to prioritized frontline healthcare workers and nursing home residents starting last week. 

The FDA’s detailed analysis determined the Moderna vaccine has a “favorable safety profile.” But the drug shares a downside with the Pfizer vaccine. Although no safety concerns barred emergency authorization, side effects are common, the agency acknowledged. These include pain at the site of injection, fatigue, fever and headache.

The Pfizer and Moderna vaccines require two doses. They also have different compositions and recommended times between doses, so recipients should have the same firm’s vaccine for each shot. Both vaccines have demonstrated roughly similar effectiveness in older people, topping 90%.