When Oregon health officials found themselves trapped on a road in a snowstorm, they walked car to car to administer leftover COVID-19 vaccine doses.

The staff and volunteers from Josephine County Public Health Department held a mass vaccination event at a high school Tuesday before getting trapped in the storm, they said.

"The team had six doses of COVID-19 vaccinations left to administer," but the doses would have expired before reaching their next destination, the department said.

"Not wanting to waste any doses, dedicated JCPH staff members began walking from car to car, offering stranded motorists a chance at receiving the vaccine," the department said. "In the end, all six doses were administered," including one to a sheriff’s office employee who had missed the mass vaccination event.

Andy Slavitt, a senior White House adviser for COVID-19, said Wednesday that any vaccine "stockpile that may have existed previously, no longer exists."

"We are taking action to increase supply and increase capacity. But even so, it will be months before everyone who wants a vaccine will be able to get one," Slavitt said. "Our practice is to maintain a rolling inventory of two to three days of supply that we can use to supplement any shortfalls in production and to ensure that we are making deliveries as committed. But we are passing doses directly along to states, very much in real time as they ordered them."

Jeff Zients, the new White House coordinator on COVID-19, said the U.S. Department of Health and Human Services will amend its rules to allow doctors and nurses who have recently retired to administer shots. They also plan to allow people licensed to vaccinate in their state to do so across state lines.

Over 23.5 million vaccine doses have been administered in the United States so far, according to the latest data from the Centers for Disease Control and Prevention.

ABC News’ Anne Flaherty and Sophie Tatum contributed to this report.

The United Kingdom now has the highest COVID-19 transmission and death rates of any country in the world, according to the World Health Organization's weekly epidemiological report released Wednesday.

With 383.1 new cases of COVID-19 per 100,000 residents, the U.K.'s transmission rate is higher than that of the United States, which decreased by 20% over the previous week to 380.6 new cases per 100,000 residents. But the UK appears to be moving in the right direction -- this week showed a 24% decrease in new cases confirmed from the previous week, the report said.

The U.K.'s COVID-19 death rate is also the world's highest, with 12.9 fatalities from the disease per 100,000 residents. The country -- which is made up of England, Scotland, Wales and Northern Ireland -- saw a 13% increase in new deaths over the previous week, according to the report.

In the U.S., the COVID-19 death rate went down by 7% to 6.5 fatalities per 100,000 residents, the report said.

As of Monday, 70 countries have detected cases of a new, more contagious variant of the novel coronavirus that was first identified in the U.K., while 31 nations have cases of another variant that first emerged in South Africa and eight countries have cases of a variant that was first identified in Brazil, according to the report.

ABC News’ Christine Theodorou contributed to this report.

Welsh authorities said Wednesday they are responding to "an ongoing incident" after a suspicious package was found at a key factory in the United Kingdom's supply chain for COVID-19 vaccines.

The plant, located in the Wrexham Industrial Estate in Wrexham, Wales, is owned by Indian biotechnology company Wockhardt, who have a partnership with British-Swedeish pharmaceutical giant AstraZeneca to manufacture its COVID-19 vaccine in the U.K.

"Wockhardt UK in Wrexham this morning received a suspicious package to site," the company said in a statement to ABC News. "All relevant authorities were immediately notified and engaged. Upon expert advice we have partially evacuated the site pending a full investigation. The safety of our employees and business continuity remain of paramount importance."

North Wales Police told ABC News in a statement: "We are currently dealing with an ongoing incident on the Wrexham Industrial Estate. The roads are currently closed and we would ask the public to avoid the area until further notice."

ABC News' Guy Davies contributed to this report.

As of Thursday, the city of Los Angeles had vaccinated 152,612 people against COVID-19 at five city-run vaccination sites. The problem, Los Angeles Mayor Eric Garcetti said, is supply. The city needs more vaccines.

Though California has said eligibility may go by age, Garcetti asked for flexibility Thursday so the city can get vaccines into communities where people are disproportionately dying -- specifically communities of color.

"The next group designated to be moved into receiving the vaccines in the coming weeks will be our workers in emergency services, as well as food and education and child care," Garcetti said.

The city has increased vaccine rollout by 17% since last week, Garcetti said, and its Dodger Stadium site is vaccinating 12,000 people per day. The entire county received 137,000 doses this week and expects 188,000 next week, according to Los Angeles County Public Health Director Dr. Barbara Ferrer.

"The city has distributed 81% of the doses that we have received," the mayor said. "This number is among the highest in the country, higher than many of our peer cities."

COVID-19 stats continue to improve in the hardest-hit county in America. Hospitalizations were down 3% and cases were down 3.4% from Wednesday, Garcetti said. However, Los Angeles County still reported 273 deaths from the disease on Thursday, crossing 16,000 total.

ABC News' Cammeron Parrish contributed to this report.