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.

Sputnik V, a COVID-19 vaccine developed by Russia, has been registered by the Palestinian Ministry of Health for emergency use in Palestinian self-ruled territory, Russia's sovereign wealth fund announced Monday.

The first shipment of doses is expected to arrive next month, according to a press release from the Russian Direct Investment Fund (RDIF), which is responsible for worldwide marketing of the vaccine.

The RDIF didn't say how many doses would be shipped to the Palestinian Authority -- which governs parts of the West Bank under interim peace deals with Israel -- but that supplies would be facilitated by manufacturing partners in India, China, South Korea and other countries.

As of Jan. 5, the World Health Organization had recorded more than 157,000 confirmed cases of COVID-19 in the occupied Palestinian territories, including at least 1,578 deaths.

ABC News' Patrick Reevell contributed to this report.