Margaret Keenan, the 91-year-old grandmother in the United Kingdom who was the first in the world (outside of clinical trials) to get the Pfizer vaccine, got her second dose on Tuesday.

Keenan, then 90, received her first dose on Dec. 8.

ABC News’ Rashid Haddou contributed to this report.

Dr. Anthony Fauci says the pandemic has “gotten out of control” and warned that January may be worse than December.

“That is what we're concerned about,” Fauci told CNN. “That in addition to the surge, we're going to have an increase … which could make January even worse than December. I hope not, I hope that doesn't happen, but it certainly is possible.”

“I think we just have to assume that it’s gonna get worse,” he said.

In terms of vaccines administered so far, Fauci said, “We certainly are not at the numbers that we wanted to be at the end of December.”

Over 11.4 million vaccine doses have been distributed and 2,127,143 Americans have received their first vaccine dose, according to the CDC.

Fauci said he believes there’ll be “an increase in the momentum” of vaccinations in January.

“Not being responsible myself for the rollout, I can't personally guarantee that we’re gonna catch up,” Fauci said. “I hope we do.”

Assistant Secretary for Health Adm. Brett Giroir said the data on people vaccinated is delayed.

“We know that’s underreported because there’s a three to seven-day delay. But we expect that to ramp up,” Giroir told MSNBC Tuesday..

ABC News’ Brian Hartman contributed to this report.

A preliminary analysis from Public Health England found that the new COVID-19 variant detected in the United Kingdom isn’t more deadly than the prior dominant variant.

It’s still likely that the new variant is more easily transmissible, because of the speed at which it has outpaced the prior variant.

This new variant now accounts for over half of the new positive cases in the U.K., the study said.

The variants are all the same virus, no matter their small genetic differences. SARS-COV-2 is a respiratory virus, meaning it is transmitted through droplets, so masks and social distancing still work to slow transmission, no matter the variant.

In addition to several European nations, the variant has also been reported in North America and Asia.

ABC News’ Ian Pannell, Sony Salzman and Christine Theodorou contributed to this report.

Russian Deputy Prime Minister Tatiana Golikova told reporters Monday that Russia’s total number of deaths from all causes during the pandemic has risen by 13.8% between January and November compared to the same period last year.

Of those excess deaths, Golikova said 81% of them were caused by COVID-19.

Data released by Russia’s state statistics agency shows that Russia has recorded 230,000 more deaths this year compared to 2019. If 81% of those are COVID-19 related, then the country’s total COVID-19 death toll is 186,000.

That is three times more than the official death toll published by the country’s health authorities (54,000).

A total of 186,000 fatalities would bring Russia’s death toll to the third worst in the world behind the U.S. and Brazil.

ABC News’ Patrick Reevell contributed to this report.

Public Health England does not recommend mixing COVID-19 vaccines from different suppliers, according to the agency's head of immunizations, Dr. Mary Ramsay.

"We do not recommend mixing the COVID-19 vaccines -- if your first dose is the Pfizer vaccine you should not be given the AstraZeneca vaccine for your second dose and vice versa," Ramsay said in a statement Saturday. "There may be extremely rare occasions where the same vaccine is not available, or where it is not known what vaccine the patient received. Every effort should be made to give them the same vaccine, but where this is not possible it is better to give a second dose of another vaccine than not at all."

The clarification comes amid questions over the British government's updated guidance on COVID-19 vaccines, which now says that if individuals who received the first shot go to an immunization site where that same vaccine is not available for a second shot, or if the first vaccine received is unknown, "it is reasonable to offer one dose of the locally available product to complete the schedule."

"This option is preferred if the individual is likely to be at immediate high risk or is considered unlikely to attend again," the guidance adds.

The guidance, which was updated Thursday, also notes that "there is no evidence on the interchangeability of the COVID-19 vaccines although studies are underway," and thus "every effort should be made to determine which vaccine the individual received and to complete with the same vaccine."

Next week, the United Kingdom is set to begin distribution of a COVID-19 vaccine developed by England's University of Oxford and manufactured by British-Swedish pharmaceutical giant AstraZeneca, after the drug was approved Wednesday for emergency supply. Another COVID-19 vaccine developed by U.S. pharmaceutical giant Pfizer and its German partner BioNTech was approved in the U.K. on Dec. 2 and rollout began a week later.

ABC News' Zoe Magee contributed to this report.