Moderna's COVID-19 vaccine received emergency use authorization from the Food and Drug Administration, the agency announced Friday night, paving the way for distribution across the country.

About 20 million doses will be delivered to the U.S. by the end of the month, according to Moderna. It will be delivered to 3,285 locations, Operation Warp Speed officials said.

The authorization of the Moderna vaccine will result in more rural communities and nursing homes beginning to see shipments of the immunization, Army Gen. Gustave Perna, COO of Operation Warp Speed, said Wednesday.

The manufacturing of the Moderna vaccine will take place in the U.S., according to Perna.

"Because of ... the planning and what was available, we were able to send out more Moderna on the first dose than we were able to send out on Pfizer — almost double," Perna said.

The Army Corps of Engineers has worked with Moderna to increase the company's manufacturing capacity for the vaccine, Health and Human Services Secretary Alex M. Azar said in a press conference Wednesday.

The distribution of coronavirus vaccines began with the Pfizer vaccine last week. Packing occurred Dec. 12, relocation occurred Dec. 13 and the first deliveries took place Dec. 14.

"Now we're starting our drumbeat of continuous execution of vaccine," Perna said in a press conference Monday.

The distribution of Moderna's vaccine will be similar to Pfizer's, according to Perna, who said distribution would "hit initial sites on Monday, follow on Tuesday and Wednesday, and then by the end of the week we're just in a routine cadence of execution."

Unlike Pfizer, Moderna will work through McKesson for distribution rather than going directly from manufacturing sites to immunization locations using FedEx and UPS. So, vaccines will move from Moderna's manufacturing facilities to McKesson distribution centers, where the filled and finished products will be packed and the addresses of the final delivery location will be added. FedEx and UPS will then handle final delivery.

The temperature requirements are the main point of differentiation between the manufacturers' vaccines, with Moderna's presenting fewer cold chain hurdles than Pfizer's.

Perna said the distribution of vaccines will take a break on Christmas Day. Packing will then resume the following Sunday.