The World Health Organization has added another version of the novel coronavirus to its list of "variants of interest" amid concerns it may mutate to the point of evading the immunity people have developed from vaccination or past infection.

The so-called mu variant, also known as B.1.621, was added to the list on Monday after it was detected in 39 countries around the world.

"The Mu variant has a constellation of mutations that indicate potential properties of immune escape," the WHO said in its COVID-19 weekly epidemiological update published Tuesday. "Preliminary data presented to the Virus Evolution Working Group show a reduction in neutralization capacity of convalescent and vaccinee sera similar to that seen for the Beta variant, but this needs to be confirmed by further studies."

American drugmaker Moderna and its Japanese distribution partner Takeda Pharmaceutical Co. announced Wednesday that they are planning to recall three suspended lots of COVID-19 vaccine doses in Japan after an investigation discovered stainless steel contaminants.

Last week, the Japanese government suspended use of the batches, containing about 1.63 million doses of Moderna's COVID-19 vaccine, following reports of foreign substances in some unused vials at multiple inoculation sites. Moderna told ABC News that one of the three lots received "several complaints of particulate matter" in its vials, while the two other adjacent lots were put on hold out of "an abundance of caution" and for continued assurance of quality.

An analysis confirmed the contaminants to be high-grade stainless steel, commonly used in manufacturing and food processing. The most probable cause of contamination was related to friction between two pieces of metal installed in the stoppering module of the production line due to an incorrect set-up. The contamination only impacted the lots that were included in the suspension, according to a joint press release from Moderna and Takeda.

The investigation was conducted by Moderna in partnership with Takeda and ROVI, the Spanish manufacturer that operates the production plant where the contamination occurred.

Japan's Ministry of Health, Labor and Wealth said in a statement Wednesday that, based on the companies' investigation, it is unlikely the stainless steel particles pose any additional health risk.

The contamination raised further concern after two men, aged 30 and 38, died in Japan within days of receiving their second doses of the Moderna vaccine from one of the suspended lots. The cause of death in both cases remains under investigation.

Moderna and Takeda said there is currently no evidence that the fatalities were caused by the vaccine.

"The relationship is currently considered to be coincidental," the companies said in a joint statement Wednesday.

The World Health Organization opened a center in Berlin on Wednesday that will gather, assess and share information internationally to help prepare for the next global health crisis.

The so-called "WHO Hub for Pandemic and Epidemic Intelligence" is receiving an initial investment of $100 million from Germany and will be led by Dr. Chikwe Ihekweazu, director-general of Nigeria's Center for Disease Control. The facility "will harness broad and diverse partnerships across many professional disciplines, and the latest technology, to link the data, tools and communities of practice so that actionable data and intelligence are shared for the common good," according to a press release from the WHO.

"The world needs to be able to detect new events with pandemic potential and to monitor disease control measures on a real-time basis to create effective pandemic and epidemic risk management," Dr. Tedros Adhanom Ghebreyesus, director-general of the WHO, said in a statement Wednesday. "This Hub will be key to that effort, leveraging innovations in data science for public health surveillance and response, and creating systems whereby we can share and expand expertise in this area globally."

"All the work that goes into pandemic and epidemic preparedness must occur before an outbreak starts," Tedros added. "Data linkage and analysis, and the ability to better detect and assess risks of disease events in their earliest stages before they amplify and cause death and societal disruption, is what the WHO Hub will focus on."

The ongoing coronavirus pandemic was the impetus for the hub's creation.

"Despite decades of investment, COVID-19 has revealed the great gaps that exist in the world’s ability to forecast, detect, assess and respond to outbreaks that threaten people worldwide," Dr. Michael Ryan, executive director of the WHO’s Health Emergency Program, said in a statement Wednesday. “The WHO Hub for Pandemic and Epidemic Intelligence is designed to develop the data access, analytic tools and communities of practice to fill these very gaps, promote collaboration and sharing, and protect the world from such crises in the future.”

On average, approximately 12,200 Americans are being admitted to the hospital each day with COVID-19. The forecast models used by the CDC suggest that by Sept. 27, that number could surge to as high as 22,400 a day.

The lower end of the forecast puts the daily hospital admissions at around 6,400.

There are signs the rate of hospital admission nationwide may be slowing, with the U.S. Centers for Disease Control and Prevention reporting hospital admissions will likely "remain stable or have an uncertain trend over the next 4 weeks."

Kentucky currently tops the list of states expected to see the most hospital admissions, per capita, in the next two weeks, followed by Florida and Georgia.

-ABC News' Arielle Mitropoulous

A new study by the U.S. Centers for Disease Control and Prevention estimates that roughly 83% of blood donors in the nation have either been vaccinated against COVID-19 or were previously infected with the virus.

This, however, does not mean that more than 80% of Americans are immune from infection. That's because neither vaccination nor prior infection provides 100% protection -- antibodies are just one part of the overall immune response, and immunity wanes over time. The analysis also may overestimate the portion of people with antibodies because blood donors may be more likely to be vaccinated or have previously been infected.

The study, posted online Tuesday by JAMA Network Open, a monthly open access medical journal published by the American Medical Association, took a snapshot of the presence of antibodies from COVID-19 vaccination or prior infection in about 1.4 million donated blood samples from across the United States. The repeated cross-sectional analysis was conducted each month during July 2020 through May 2021, before delta became the predominant variant of the novel coronavirus in the U.S.

The study shows that the number of blood donors who tested positive for antibodies, indicating either vaccination or prior infection, has gone up over time, from 3.5% in July 2020 to 20.2% for infection-induced antibodies and 83.3% for both infection- and vaccine-induced antibodies in May 2021.

Being vaccinated offers better protection compared to prior infection, and it's recommended that people who have previously contracted COVID-19 should still get inoculated.

-ABC News' Katie Bosland and Sony Salzman