The latest leg of a massive vaccination effort took place in a distribution center in Olive Branch, Miss. There, vials with the nation’s second coronavirus vaccine were loaded into boxes, ready to head out across the country to help states gripped by the surging pandemic.

Shipments of the second vaccine, developed by Massachusetts biotechnology company Moderna in partnership with the National Institute of Allergy and Infectious Diseases, are set to arrive in states beginning on Monday. The Food and Drug Administration gave emergency authorization to Moderna’s shot Friday, one week after granting emergency authorization to the first vaccine by Pfizer and BioNTech.

The vials will provide another tool in the fight against the pandemic that has killed more than 316,000 people in the United States — a death toll that is precipitously rising, as some states report unnerving numbers and set daily records. The vaccine is another two-shot regimen and will be easier to transport because it can be stored at normal freezer temperatures, while Pfizer’s shots need to be kept at ultracold temperatures

But officials warn the nation is still reeling from infections seeded over Thanksgiving and worry about additional surges that could follow the December holidays.

“Unfortunately, it will get worse,” Moncef Slaoui, chief science adviser to the White House’s effort to develop a vaccine, said in an interview on CNN’s “State of the Union.” “There will be a continuing surge. Exactly what the numbers may be, I don’t know. But, unfortunately, they’re going to be higher than what they are today, most likely.”

But, Slaoui added: “There is light at the end of tunnel.”

He said he expected the first shot of the latest vaccine to be doled out on Monday, as 7.9 million total doses of the Moderna and Pfizer vaccines are set to be shipped this week.

Adm. Brett Giroir, assistant secretary of health and human services, urged Americans to continue to take precautions ahead of the holidays.

“Really, the lives of tens of thousands of Americans depend on what we do. And you know what to do,” he said during an interview on ABC News’s “This Week.” “It’s wearing a mask when you’re in public, physically distancing, washing your hands. If you’re having holiday gatherings, please do them safely. Try to limit them to your immediate household. And if you don’t, wear masks inside, improve the ventilation.”

He said while widespread vaccination will eventually end the pandemic, “we’ve got a lot of work to do, or it’s going to be an even darker winter.”

President-elect Joe Biden and his wife, Jill, will receive the vaccine on Monday. Vice President-elect Kamala D. Harris and her husband, Doug Emhoff, will get their first vaccine shots the following week. Vice President Pence, as well as numerous congressional leaders, received their shots on Friday.

Vice President Pence and second lady Karen Pence received the Pfizer-BioNTech coronavirus vaccine on Dec. 18 at the Eisenhower Executive Office Building. (The Washington Post)

President Trump has not announced vaccination plans. In a tweet on Dec. 13, he said, “I am not scheduled to take the vaccine, but look forward to doing so at the appropriate time.”

Giroir suggested the president’s vaccination would encourage his supporters to get their shots as well.

“I would encourage the president to get a vaccine for his own health and safety and also to generate more confidence among the people who follow him so closely,” Giroir said.

Surgeon General Jerome M. Adams, in an interview on CBS News’s “Face the Nation,” cited the antibody treatment Trump received after contracting the coronavirus earlier this year as a reason the president has not yet received a vaccine.

“From a scientific point of view, I will remind people that the president has had covid within the last 90 days,” Adams said. “He received the monoclonal antibodies. And that is actually one scenario where we tell people maybe you should hold off on getting the vaccine, talk to your health provider to find out the right time.”

The White House did not immediately respond to an inquiry about whether the president has made plans to get a coronavirus vaccine.

During his interview on CNN, Slaoui said it is “appropriate” for people who have already been infected with the virus to get vaccinated. “It’s safe,” he said, adding that being infected with the virus “doesn’t induce a very strong immune response and it wanes over time.”

Trump administration officials have eyed a midyear timeline for when a large proportion of the population could be vaccinated. Giroir expressed confidence on Sunday that by June, “anyone in America who wants to have a vaccine will have that opportunity to have a vaccine.”

Biden’s surgeon general pick, Vivek H. Murthy, who served in the role during the Obama administration, warned a late Spring timetable for mass vaccination may be too optimistic.

“If everything goes well, then we may see a circumstance where by late spring, you know, people who are in lower-risk categories can get this vaccine, but that would really require everything to go exactly on schedule,” Murthy said on NBC News’s “Meet the Press.” “I think it’s more realistic to assume that it may be closer to midsummer or early fall when this vaccine makes its way to the general population. So, we want to be optimistic, but we want to be cautious as well.”

Joseph Marks contributed to this report.