California's regional stay-at-home order has been extended for Southern California and San Joaquin Valley, officials announced Tuesday.

Driving the news: The expected move came as the ICU capacity in both regions remained at 0%, the state health department said. Southern California and San Joaquin Valley have been under the order since Dec. 6.

Colorado's health department discovered the new variant of the coronavirus that may be more transmissible, Gov. Jared Polis announced on Tuesday.

Why it matters: It's the first known U.S. case of the variant, which was initially discovered in the United Kingdom.

The European Union began on Sunday a coordinated rollout of coronavirus vaccinations across its 27 member states in a drive to inoculate some 450 million people.

Why it matters: Several European countries have tightened restrictions as cases, deaths and hospitalizations surge. EU countries have recorded at least 16 million COVID-19 cases and 336,000 deaths since the pandemic began, per AP.

Mexico became the first Latin American country to begin coronavirus vaccinations, amid a surge in cases, the New York Times reports.

Why it matters: The serum arrives as Mexico's hospitals reach a breaking point. The country tallies over 1.3 million COVID-19 cases and 120,000 deaths, per John Hopkins University data, though actual numbers are believed to be much higher.

2020 will go down in infamy for all the obvious reasons, but history shows it doesn't actually rank among humanity's worst years.

Why it matters: The past is a foreign country, and that goes doubly so the deeper we dig. Understanding just how far we've come from the years when life was nasty, brutal and short can help us put the pain of 2020 in perspective, and appreciate the progress we need to defend.

You've received a coronavirus vaccination — but can you prove it? The answer to that question will help determine how the global economy functions for the next few years.

Why it matters: The federal government will probably neither mandate nor encourage digital immunity passports or other proofs of vaccination. But privately-operated digital certificates are already being developed — and U.S. law means that anybody who gets vaccinated here should be able to obtain the proof they need.

San Francisco will enforce a travel quarantine effective Friday as California struggles to combat rising COVID-19 deaths and hospitalization rates.

Driving the news: Anyone “traveling, moving or returning to San Francisco from anywhere outside the Bay Area” will have to remain isolated for 10 days, Mayor London Breed announced on Thursday. The order will remain in place through at least Jan. 4.

There were nearly 12,000 more deaths than expected among young adults between March and July, according to new research published Wednesday in JAMA.

Why it matters: Only 38% of deaths in this age group were attributed directly to COVID-19, which suggests that COVID-19–related mortality may have been under-detected.

Pfizer vaccine vials contain extra doses that could boost America's supply by up to 40%, the Food and Drug Administration announced on Wednesday.

Driving the news: The U.S. has 100 million doses of the Pfizer-BioNTech vaccine to inoculate 50 million people but declined to buy more doses earlier this year. The vaccine is first being administrated to frontline health care workers and nursing home residents and staff.

A western Kansas mayor submitted a letter of resignation Tuesday after receiving threats to her wellbeing for her public support of a face mask mandate.

Why it matters: Public officials have received increasing backlash and threats for actions taken to curb the spread of COVID-19.