(CNN)Republicans on the House Judiciary Committee deleted a tweet Friday morning that spread disinformation about Covid-19 booster shots.

The false tweet from the House Judiciary Committee Republicans' official account, which was posted Thursday afternoon, read: "If the booster shots work, why don't they work?" The tweet received a wave of backlash before it was taken down and came at a time when Covid cases are spiking across the US following the Omicron variant's emergence, and public health experts are encouraging people to get boosted to protect themselves and others.

While most Republicans have said they support Covid-19 vaccines but oppose mandates, many members of the GOP -- especially those on the far-right -- have continued to spread disinformation, conspiracy theories and anti-vaccine sentiments. Elected Republicans have crusaded against mandates as part of their resistance to the Biden administration's pandemic response efforts.

According to CNN's latest polling, a 65% majority of Republicans and Republican-leaning independents report having received at least one dose of a Covid vaccine. (By contrast, only about one-quarter see vaccination requirements as an acceptable way to increase the vaccination rate.)

WASHINGTON, Dec 30 (Reuters) - U.S. health experts on Thursday urged Americans to prepare for severe disruptions in coming weeks as the rising wave of COVID-19 cases led by the Omicron variant threatened hospitals, schools and other sectors impacting their daily lives.

The warning came as the United States reached a record high in COVID-19 cases, while federal officials issued more travel warnings and reportedly prepared to authorize booster shots for 12 to 15-year-olds next week.

For the second day in a row, the United States had a record number of new reported cases based on the seven-day average, with more than 290,000 new infections reported each day, a Reuters tally showed.

At least 18 states and Puerto Rico have set pandemic records for new cases, according to the tally. Maryland, Ohio and Washington, D.C., also saw record hospitalizations as overall U.S. COVID-19 hospitalizations rose 27%.

NEW YORK, Dec 30 (Reuters) - U.S. prosecutors decided to end their criminal case against two Manhattan jail guards who admitted to falsifying records on the night the financier Jeffrey Epstein killed himself on their watch.

In a Thursday filing in Manhattan federal court, prosecutors asked a judge to dismiss claims against Tova Noel and Michael Thomas, after both complied with the six-month deferred prosecution agreements they agreed to in May.

Epstein was found hanging in his cell at the Metropolitan Correctional Center on Aug. 10, 2019, while awaiting trial for sex trafficking, in what New York City's medical examiner called a suicide.

Noel and Thomas were accused of falling asleep and surfing the internet that night rather than checking on Epstein every 30 minutes.

Amtrak said Thursday that it will reduce its schedule between New Year’s Eve and Jan. 6 as it battles bad weather in some parts of the country and a surge in coronavirus cases among its employees.

About two dozen trains on both its Northeast Corridor and long-distance routes will be affected.

“Amtrak regrets any inconvenience,” the railroad said in a statement. “We are continuing to monitor changing conditions and will make any further adjustments as required.”

Amtrak says 97 percent of its workforce is vaccinated against the coronavirus, but it has seen an increase in positive cases in line with the surge around the country. The railroad had said this week the surge wasn’t leading to cancellations.

UW Medicine will soon start limiting its COVID-19 testing appointments to include only those with symptoms or known exposures because of an “astronomically high” positivity rate that’s slowing the testing process, the health care system announced Thursday.

Of UW Medicine’s 12 community testing sites, nine will soon start limiting appointments. Three, however, including in Ballard, and at Seattle City Hall and Lake Sammamish State Park, will close temporarily.

The high positivity rate — measuring more than 40% at some South King County testing sites — is creating a challenge in UW Medicine’s testing process and slowing scientists’ ability to parse out which samples are actually positive, Dr. Geoff Baird, chair of laboratory medicine and pathology at UW Medicine, said in a news briefing Thursday morning.

UW scientists normally opt for a “pool testing” system — common throughout the country — to speed up the testing process, which means they take four or five samples from testing sites, extract a small portion of each, then mix them together in one vial for testing.

Another round of snow and continued pandemic-induced staffing problems brought an unwanted distinction to Seattle-Tacoma International Airport: for the second day in a row, the airport had more cancelled flights than any other airport on the planet.

As of 10 a.m. Thursday, airlines had canceled 289 arrivals and departures at Sea-Tac Airport — more than a quarter of all of Thursday’s scheduled flights, and the highest number of any airport in the world — according to the website FlightAware.com.

The cancellations, which scrapped 148 departures and 141 arrivals, bring Sea-Tac’s cancellation total to more than 1,450 since Sunday, when heavy snow on top of ongoing staffing issues began snarling domestic air travel, according to the flight tracking site.

Thursday’s cancellations brought more frustration for many travelers who had already been hit by cancellations that were starting to surge even before Christmas.