Who could have predicted on Jan. 1, 2020, that a coronavirus invisible to the human eye would change life for nearly every person on the planet and kill more than a million people? Viruses do not catch God by surprise, but SARS-CoV-2 surprised the world, spreading quietly and rapidly. Its incubation period (up to 14 days) and tendency to infect some people asymptomatically while causing severe COVID-19 or death in others made the virus especially difficult to contain.

The United States’ northern neighbors should start getting immunized against the coronavirus within days, and the United Kingdom began rolling out the shots this week. The U.S. Food and Drug Administration’s independent advisers plan to meet Thursday to debate whether Pfizer and its partner BioNTech have presented sufficient evidence of the vaccine’s safety and effectiveness to grant emergency use authorization. If they approve it as expected, distribution could begin within days.

On average, more than 2,200 Americans per day are dying from the coronavirus, reaching April’s high levels. More than 200,000 test positive for the virus daily, and cases are rising in all states. Much of Southern California has imposed stringent new lockdowns this week as COVID-19 patients fill ICU beds.

British Health Secretary Matt Hancock dubbed Tuesday “V-Day” in the fight against the pandemic, harkening back to the final days of World War II. This time, the V stands for “vaccine,” instead of “victory.” The country authorized widespread use of Pfizer and BioNTech’s COVID-19 vaccine and 90-year-old Margaret Keenan received the first dose today. The vaccine will go to nursing home workers and older people first—most will have to wait until after the new year to get the shot.

The president-elect has previously pushed for a nationwide mask mandate to stop the spread of the coronavirus. But on Thursday, Joe Biden stopped short of that, saying his first act as president would be asking Americans to commit to wear face coverings for his first 100 days in office.

Dr. Robert Redfield, head of the U.S. Centers for Disease Control and Prevention, said Wednesday that December and January could “be the most difficult time in the public health history of this nation.” More than 3,100 Americans died of the coronavirus on Wednesday, more than the previous high of 2,603 set on April 15, according to Johns Hopkins University. The COVID Tracking project reported that the number of U.S. hospitalizations passed 100,000 for the first time.

Americans who choose to travel for Christmas should consider getting tested for the coronavirus a few days before leaving and after coming back, the U.S. Centers for Disease Control and Prevention said Wednesday. But the agency also repeated what it said about Thanksgiving: The best way to slow the spread of the virus is to stay home. Nearly 1.2 million Americans passed through U.S. airports on Sunday anyway.