With the federal government possibly only weeks away from approving a coronavirus vaccine, Maine health officials are preparing to get the shots delivered, stored at hospitals and administered to those who will first receive the vaccine.

Pfizer Inc. officials said on Monday that a potential coronavirus vaccine is showing great promise, and has a potential 90 percent effectiveness rate according to late-stage research trials. A 90 percent effectiveness rate would be much better than annual influenza shots – which have a typical effectiveness range of between 40 and 60 percent – and more in line with highly effective childhood vaccinations, such as for varicella, polio and measles.

For Pfizer’s COVID-19 vaccine, the next step would be a Food and Drug Administration emergency use authorization – perhaps as soon as late November – followed by manufacturing 50 million doses by the end of 2020. The federal government signed an agreement with Pfizer this summer for the pharmaceutical company to distribute its first 100 million doses in the United States.

But the Pfizer vaccine – while showing encouraging effectiveness in studies – poses logistical challenges because it needs ultra-cold storage, Dr. Nirav Shah, director of the Maine Center for Disease Control and Prevention, said in a briefing with reporters Monday.

Other vaccines, such as a candidate being developed by Massachusetts-based Moderna, do not need super-cold storage. Moderna also is in late-stage development and could receive emergency use approval shortly after the Pfizer vaccine.

Shah said the Pfizer vaccine needs to be stored at minus 80 Celsius (minus 112 degrees Fahrenheit), so the Maine CDC is preparing in case the Pfizer vaccine is the first one across the finish line.

“We are working to expand the scope of ultra-cold storage we have in Maine,” Shah said. “It is definitely a logistics challenge, but this is what we do at the Maine CDC and DHHS. We take tough logistics challenges, and we take them head on.”

He said the CDC has been working with Maine hospitals on how to store the Pfizer vaccine and is purchasing one or two ultra-cold freezers to increase the state’s capacity.

The vaccine can be taken out of the deep freezers for several days before administering the shot, but Shah said getting the Pfizer vaccine to Mainers, especially in rural areas, would nevertheless be a big challenge.

And he said the need for cold storage may at least initially limit how the vaccine is administered, by having immunization clinics in more centralized locations, such as at hospitals.

“This is the type of vaccine where you bring the people to the vaccine rather than bringing the vaccine to the people,” Shah said.

He said the Moderna vaccine will likely be easier to administer to more Mainers because the cold storage requirements are minus 20 Celsius (minus 4 degrees Fahrenheit) compared to minus 80 Celsius for the Pfizer vaccine.

“The Moderna vaccine may be the one that has broader application,” Shah said.

He also cautioned that while Pfizer’s news release Monday was encouraging, he noted that the pharmaceutical company had not yet released the data from its research to support its claims, making it impossible to draw conclusions about the effectiveness of the vaccine.

In October, Maine sent a vaccine readiness plan to the U.S. Department of Health and Human Services. Among the first to be immunized would be health care workers in high-risk settings, nursing homes and other congregate care centers, and some essential workers. Next in line would be school staff, those with certain underlying health conditions, seniors and correctional centers.

Any vaccine approved in 2020 would not be widely available until well into 2021, in the late spring, summer, or even potentially early fall.

Maine says in its plan that it would have the capacity to vaccinate 80 percent of the state’s 1.3 million people within 12 weeks of when a vaccine becomes available.

When fully ramped up, Maine would be giving about 130,000 shots weekly, according to a plan released by the Department of Health and Human Services on Friday. Giving most Mainers their COVID-19 shot will be a massive undertaking that will involve thousands of health care workers, state agencies, all of Maine’s hospitals and health care networks, pharmacies, public health nurses, schools and workplaces.