COVID-19 updates: Anti-vaccine protesters halt vaccinations at Dodger Stadium

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.

American biotechnology company Regeneron Pharmaceuticals announced Wednesday that its cocktail of two monoclonal antibodies held up in laboratory experiments against new variants of the novel coronavirus first identified in the United Kingdom and South Africa.

Monoclonal antibodies are synthetic versions of our natural antibody defense to infection. They are being studied as a way to both treat and prevent COVID-19 infection, with promising results. But unlike vaccines, which are thought to offer broader protection, some scientists have been worried that this type of therapy would be less effective against newly emerging variants of the virus.

Wednesday's announcement is good news for Regeneron's monoclonal antibody treatment, REGEN-COV, though the data is still preliminary and currently under peer review.

Regeneron scientists as well as researchers at Columbia University in New York City have each independently confirmed that the casirivimab and imdevimab antibody cocktail successfully neutralized both the U.K. and South Africa variants when tested against them, according to a company press release.

REGEN-COV has not yet been tested against another variant that was first identified in Brazil. However, Regeneron said the two-antibody cocktail "is expected to remain similarly potent" based on some resemblance which the Brazil variant bears to the South Africa strain. The company said it is pursuing further confirmatory research.

It's the latest piece of promising news about the efficacy of monoclonal antibodies as treatment for COVID-19. On Tuesday, American pharmaceutical firm Eli Lilly and Company announced that a combination of two monoclonal antibodies, bamlanivimab and etesevimab, was found to be effective in COVID-19 patients at high risk of severe infection, reducing the risk of hospitalization and death by 70%, according to the results of a final-stage trial.

That same day, Regeneron announced its antibody cocktail had shown positive initial results in prophylactic use -- that is, helping ward off COVID-19 in those who may have been exposed to the virus. Regeneron’s chief scientific officer, Dr. George Yancopoulos, said he hopes the drug "may be able to help break this chain" of active infection and transmission.

Last Thursday, Eli Lilly released data showing bamlanivimab may help prevent disease and stop outbreaks among residents and staff of long-term care facilities.

ABC News' Sasha Pezenik contributed to this report.