MORRISVILLE, N.C. — President Trump and Vice President Pence hit the road on Monday to highlight progress on the development of a vaccine for COVID-19, seeking to project optimism about the administration's response to a pandemic that has killed more than 145,000 people in the U.S.

Trump visited a biotech facility here to boast of the rapid progress on finding a vaccine to combat the pandemic, claiming his administration’s work through its vaccine development effort, Operation Warp Speed, had reduced the wait time by “years.” 

He hailed the project as a “historic initiative to develop, test, manufacture and deliver a vaccine in record time.”

Trump kicked off his remarks by noting that Moderna had officially entered phase three of clinical trials. The president, wearing a mask, also took a tour of the Fujifilm Diosynth Biotechnologies Innovation Center on Monday afternoon.

The trip to North Carolina was brief — he spent roughly an hour inside the biotech facility in total — but remained closely on message. Trump spoke optimistically of the prospects for a vaccine that experts have cautioned may not be widely available for another year, and he made scant mention of the rising number of cases most states are seeing.

Trump took an extremely abbreviated tour of the lab, appearing in front of reporters for roughly five minutes. He wore a mask for that portion of the visit, just the second time he’s done so in front of press cameras months after health officials urged the widespread use of face coverings to slow the spread of the virus.

While Trump was in North Carolina, Pence traveled to Florida to mark the start of phase three trials for a coronavirus vaccine. The vice president visited the University of Miami. The university's school of medicine is taking part in a 30,000-person study for one of the vaccine candidates being developed by Moderna.

Florida has emerged in recent weeks as the new epicenter of the pandemic in the United States, with the state reporting more than 432,000 infections total and setting records for daily infections.

The Trump administration has struggled to get a handle on the pandemic amid mixed messaging from Trump and spikes in cases around the country in recent weeks. More than 4.2 million Americans in total have been infected with COVID-19. The situation hit home for the White House on Monday when it was revealed that national security adviser Robert O'Brien had tested positive for the virus, the highest-ranking official to test positive to date. 

Trump last week resumed giving regular briefings on the coronavirus after a roughly two-month hiatus. The president signaled that the briefings would focus specifically on therapeutics and vaccine development as the White House attempts to reassert Trump as the face of the government response.

The White House halted the briefings in late April after they repeatedly got off track, with Trump sparring with reporters, bashing state leaders and musing at one point about the use of disinfectants to treat the virus.

Trump has pinned his hopes for a quick economic bounceback and return to normalcy from the pandemic on the rapid development of a vaccine. Experts have expressed optimism about the chances of having more than one approved vaccine by early 2021, citing the volume of vaccines being developed worldwide and the influx of resources from the federal government through Operation Warp Speed.

Trump, as he has previously, said Monday that he believed a vaccine could be available by the end of the year. 

"I heard very positive things, but by the end of the year, we think we're in very good shape to be doing that," the president told reporters during a briefing at the Morrisville facility. 

Pence told reporters at a separate briefing in Miami that he expected the first doses to go to the most vulnerable members of the U.S. population, specifically mentioning senior citizens. 

The administration has already invested billions of dollars into several different companies in hopes of having a successful vaccine, including Moderna, AstraZeneca and Johnson & Johnson. Earlier this month, the administration announced it would pay the small Maryland-based company Novavax $1.6 billion for its COVID-19 vaccine.

The government announced a roughly $2 billion deal last week with Pfizer and a smaller German biotechnology company for doses and distribution of a coronavirus vaccine.

But Anthony Fauci, the government's top infectious diseases expert, and other public health officials have cautioned that a successful vaccine may not be widely available until several months into 2021.

Morgan Chalfant contributed.