British health authorities reported 41,385 new COVID-19 cases Monday, the highest daily rise since the pandemic began. Over the last seven days, 256,220 people tested positive, which is a 25.7% increase in positive tests since the week prior.

England's Chief Scientific Adviser Patrick Vallance said last week that the newly identified U.K. variant is more dominant and significantly more transmissible than the old coronavirus variant.

There’s no evidence the new variants are more deadly and it’s highly likely the vaccine will still work, experts said at a virtual Q&A hosted by the World Health Organization last week.

In total, the U.K. has reported 2,329,730 infections and 71,109 deaths from the virus.

-ABC News' Christine Theodorou contributed to this report.

One out of 17 Americans, a total of 19 million people, have tested positive for coronavirus, according to data from Johns Hopkins University. One in 1,000 have died from the virus.

Since some states don't report and others give incomplete updates over the holidays, last week's data doesn't provide an up-to-date picture of the U.S. outbreak. But even without those numbers, December's forecast remains grim, according to an ABC News analysis of data from The COVID Tracking Project.

Since Dec. 1, there has not been a single day with less than 1,000 COVID-19 related deaths reported, the data showed.

The United States logged more than 5.4 million COVID-19 cases in December, more than any month on record and roughly equivalent to 70 Americans testing positive for the virus every 30 seconds.

-ABC News' Arielle Mitropoulos contributed to this report.

New Jersey vaccinated its first nursing home resident, a 103-year-old resident of Roosevelt Care Center in Old Bridge Monday.

Mildred Clements, a Newark native who has lived through two pandemics, was met by a round of applause from the governor and state health commissioner after receiving her shot. Residents and staff at roughly 90 long-term care facilities in New Jersey are slated to start vaccinations Monday, according to the governor's office.

-ABC News' Aaron Katersky contributed to this report.

The Transportation Security Administration (TSA) on Sunday saw the highest number of people screened at the airport since the pandemic hit, a spokesperson tweeted Monday.

The 1,284,599 people screened at airports nationwide marks the sixth day in the last 10 with more than 1 million airline screenings. "If you choose to travel, please wear a mask," Lisa Farbstein, the TSA spokesperson, wrote on Twitter.

-ABC News' Michael Kreisel contributed to this report.

The Centers for Disease Control and Prevention updated its guidelines for people with underlying health conditions planning to take a COVID-19 vaccine.

They CDC said that adults with underlying medical conditions -- who are more at risk of becoming seriously ill from COVID-19 -- can receive a vaccine against the virus as long as they have not had a severe allergic reaction to any of the ingredients in it.

The new guidelines state that people with HIV and those with weakened immune systems due to other illnesses or medication should be aware that information about the safety of COVID-19 vaccines for their group is not yet available. While people with HIV were included in clinical trials, more data is required to provide safety guidelines regarding the effects a vaccine could have on them. The same is true for people with autoimmune conditions.

People who have previously had Guillain-Barre syndrome or Bell’s palsy may receive a COVID-19 vaccine, though experts are still acquiring more data about their groups as well.

The CDC added that people should continue to follow coronavirus health measures -- such as wearing a mask and staying 6 feet away from others -- after receiving the shot, as experts have more to learn about the protection that COVID-19 vaccines provide under real-life conditions.