Dr. Soumya Swaminathan, chief scientist at the World Health Organization, urged people to keep practicing public health measures like mask wearing and social distancing while COVID-19 vaccine production scales up enough to reach billions of people worldwide.

"So, we have to be here a little bit patient, the vaccines are going to come, they're going to go to all countries but meanwhile we mustn't forget there are measures that work," Swaminathan said.

People around the world will need to keep practicing fundamental public health measures at least "for the rest of this year at least," according to Swaminathan.

"Even as vaccines start protecting the most vulnerable, we're not going to achieve any levels of population immunity, or herd immunity in 2021," she added.

-ABC News' Christine Theodorou contributed to this report.

President-elect Joe Biden got his second dose of the two-dose Pfizer/BioNTech vaccine on Monday in Newark, Delaware.

After two doses, the Pfizer vaccine is 95% effective.

U.S. Rep. Bonnie Watson Coleman, D-N.J. announced Monday that she has received a positive result for COVID-19 from a rapid antigen test and is awaiting results from a polymerase chain reaction (PCR) test.

Coleman said she was forced to shelter in place with unmasked colleagues last week when a mob of President Donald Trump's supporters stormed the U.S. Capitol building in Washington, D.C.

"Following the events of Wednesday, including sheltering with several colleagues who refused to wear masks, I decided to take a Covid test," Coleman, 75, wrote on Twitter. "I have tested positive."

The congresswoman, who previously received one dose of the Pfizer/BioNTech vaccine, said she is experiencing mild, cold-like symptoms and is isolating at home.

-ABC News' Mariam Khan contributed to this report.

Japan has identified a new variant of COVID-19, Dr. Tedros Adhanom Ghebreyesus, director-general of the World Health Organization, said during a Monday news conference.

Japanese health officials alerted the WHO of the new variant, which is different than COVID-19 variants first identified in the U.K. and in South Africa, over the weekend. High transmission of the virus in much of the world is giving it more chances to mutate and evolve into new variants.

"Most notably, transmissibility of some variants of the virus appears to be increasing," Tedros said. "This can drive a surge of cases and hospitalizations, which is highly problematic for health workers and hospitals already close to breaking point," he added.

"At present, the variants do not seem to show increased severity of disease," Tedros said.

-ABC News' Christine Theodorou contributed to this report.

Researchers at Ohio State University's Wexner Medical Center said Wednesday that they've have identified two new variants of the virus that causes COVID-19.

The first variant, which was found in just one person, contains a mutation that's similar to a mutation seen in the variants from the U.K. and South Africa, but it arose independently in the U.S., the researchers said. It is not known if it is more easily transmissible.

The second newly identified variant was found in about 20 patients in Columbus and also arose independently in the U.S., the researchers said. It does not contain any mutations in common with variants identified in the U.K. or South Africa, they said. Scientists said they found cases of this variant with increased frequency during late December, which could imply that it's more easily transmissible, but they emphasized that more studies are needed.

Peter Mohler, a co-author of the study and chief scientific officer at the Wexner Medical Center, said Wednesday, "we’re not ready to overreact," stressing, "this is very normal for a virus to mutate."

ABC News' Sony Salzman contributed to this report.