Sens. Bernie Sanders (Vt.) and Elizabeth Warren (Mass.) have been reluctant to go after each other when sharing the debate stage; in fact, they frequently end up agreeing with and supporting each other. The pair had a significant disagreement on Thursday night, though, when Warren swung a question about gun control around to announce her stance on the Senate filibuster.

"We have a Congress that's beholden to the gun industry," Warren said. "And unless we're willing to address that head on and roll back the filibuster, we're not going to get anything done on guns." Her campaign quickly took up the talking point on Twitter to reinforce it:

Sanders was asked afterward if he would support abolishing the filibuster as well. "No," the senator said bluntly. Sanders has said in the past that "Donald Trump supports the ending of the filibuster so you should be a little bit nervous if Donald Trump supports it," and argued that he has other ways to work the Senate rules.

But The New York Times' Astead Herndon observed that Warren coming out against the filibuster was strategic in that it "force[s] Bernie into a rare place of being an institutionalist." It seemed like people were listening, too; "filibuster" spiked 4,000 percent on Google during the debate. Jeva Lange

Researchers at the University of Oxford are looking for 64 healthy people between the ages of 18 and 30 who have recovered from COVID-19. In a new, first-of-its kind study, the volunteers will be reinfected with the original strain of the coronavirus first identified in Wuhan, China, under controlled, quarantined conditions for 17 days, the university said Monday.

The main goal of the challenge trial is to discover what levels and types of immunity are needed to prevent reinfection, which could aid vaccine developers going forward. So far, natural infections and vaccines appear to provide strong protection against reinfection for the most part, but it's unclear how long that will last. The study may also reveal how much virus it takes to reinfect a recovered patient.

While Oxford is excited about the study's potential, challenge trials have their critics, who argue that deliberately infecting someone is unethical, regardless of the circumstances. Read more at Bloomberg. Tim O'Donnell

While some countries are on an individual path out of the coronavirus pandemic thanks to their vaccination drives, that's not the norm. In fact, the world is coming off its worst ever week for COVID-19 infections, Bloomberg reports.

India and Brazil, two of the world's most populous nations, are both experiencing surges, which is contributing to the record-breaking numbers.

Analysts have warned for some time that unequal vaccine distribution would lead to these types of discrepancies. Bloomberg's David Fickling argues that the increase in cases is reflecting the varying trends around the world, though he clarifies that it actually appears to be middle-income countries, in which about two-thirds of the world's population resides, that are really falling behind on vaccinations.

Higher-income countries, like the United States, tend to have a surplus of doses, while low-income countries are receiving a significant amount on a per capita basis, as well, thanks to concentrated efforts like the COVAX, a global bulk-buying vaccine program. But the middle-income countries, including India and China, have low coverage area rates, suggesting it will still be some time before vaccinations tick up, which means the pandemic is likely far from over. Tim O'Donnell

And now, here is yet another new guest host of Jeopardy!

CNN's Anderson Cooper on Monday will step in to host Jeopardy! for two weeks, the latest in a series of guest hosts the show has brought in since Alex Trebek's death. In an interview prior to his debut, Cooper described himself as a huge fan of the show and acknowledged being "nervous" about his stint. He also honored Trebek as someone who was an "integral part of my entire youth and growing up," something he told the man himself last year.

"I got a call from him probably about a month or two before he died," Cooper said. "He was asking me about some other stuff, but I used it as an opportunity just to say to him how much I appreciated him, and what he had brought to my life and to the life of so many people. So I was really glad I got the chance to do that."

Trebek died in November 2020 following a battle with cancer, and the show since January has been temporarily hosted by former champion Ken Jennings, Jeopardy producer Mike Richards, journalist Katie Couric, TV host Dr. Oz, and quarterback Aaron Rodgers. It still hasn't been announced who will replace Trebek permanently, though Cooper has been seen as a potential contender.

"Whoever leads this show forward, there's certainly big shoes to fill," Cooper said in his interview. "And I know whoever becomes the host of this show, they're going to carry on Alex's legacy."

Jennings has also been a major fan favorite to take over the permanent role, while Rogers has said he'd like to be considered. Meanwhile, calls for LeVar Burton to at least get brought in as a guest host continue to fall on deaf ears. Brendan Morrow

The early returns on COVID-19 vaccinations have largely been positive in the United States and elsewhere. There have certainly been so-called "breakthrough" cases, in which fully vaccinated people have been infected, but The New York Times' David Leonhardt notes that statistics so far indicate the chances of that happening are about one in 11,000, and the rate dwindles even further when it comes to the chances of developing anything worse than a mild infection.

Still, many people who have been vaccinated remain nervous. This is understandable, Leonhardt writes, given the novelty of the virus and the toll it's taken. The risk of dying from COVID-19 post-vaccination is probably more akin to "high profile," but "extremely rare dangers" like plane crashes, lightning strikes, or shark attacks. Getting in a car, on the other hand, is a "bigger threat," Leonhardt writes.

FiveThirtyEight's Nate Silver and data scientist David Shor also made this point, and Shor noted that the "per hour risk of killing somebody driving sober is at least 33 times higher than the per hour risk of killing somebody from [COVID-19] hanging out maskless post-vaccination."

That's where sociologist Zeynep Tufekci jumped in. Tufekci generally agrees that COVID-19 vaccination leads to a "dramatic risk reduction." She does, however, think the risks of driving and doing certain activities while vaccinated are not completely comparable. That's because car accidents are generally more individualized, while spreading COVID-19 can lead to a transmission chain, which is why Tufekci thinks government agencies need to be explicit about how effectively the vaccines curb transmission to determine what the true risk factor is. Tim O'Donnell

At this point, Natalie Shure writes in The New Republic, the "ongoing ubiquity" of outdoor masking has turned into "meaningless political theater," even as the coronavirus pandemic continues.

The Atlantic's Derek Thompson seems to concur, writing that "mandating outdoor masks and closing public areas makes a show of 'taking the virus seriously,' while doing nothing to reduce indoor spread,'" adding that such rules may actually backfire in that they force people to gather inside, which is much riskier. Slate's Shannon Palus joined Shure and Thompson in arguing that outdoor masking makes little sense anymore, given how much more information there is about COVID-19 transmission these days.

Shure, Thompson, and Palus were quick to clarify that they're still very much in favor of wearing masks indoors, but they all pointed to several studies that found the risk of passing on the virus outdoors to be very small. The rare cases that do occur tend to "involve considerable close contact," as opposed to, say, "passing someone maskless on the street or in the park," Shure writes.

The counterargument is that wearing masks outdoors reinforces the idea that people should wear them indoors, but Thompson notes that Julia Marcus, a Harvard Medical School epidemiologist, found through some anecdotal interviews with mask skeptics that people became more open to adhering to indoor mandates when they learned outdoor masking wasn't as important. "The purpose of mask wearing isn't to send a message," Shure writes. "If it were we could just iron whatever slogan we wanted to onto a T-shirt. The point of mask-wearing is to reduce infection, and there's simply no reason to believe that wearing a mask while walking to the grocery store accomplishes this." Read more at The Atlantic, The New Republic, and Slate. Tim O'Donnell

Meet the latest addition to Earth's mightiest heroes.

Marvel Studios on Monday debuted the teaser trailer for Shang-Chi and the Legend of the Ten Rings, its very first superhero movie centered around an Asian lead.

Simu Liu stars as the titular Marvel superhero. In the film, Shang-Chi is living in America after training to become an assassin under his father but walking away from it all, "only to find himself sucked back into his father's sinister domain," Entertainment Weekly writes.

Director Destin Daniel Cretton explained to Entertainment Weekly that the film tells a story about Asian identity and that its crew was a "big mix of Asian cultures coming together," while star Awkwafina added that she saw a "level of Asian representation that I haven't seen" while working on it. Liu also told Entertainment Weekly that although Shang-Chi draws from Marvel's comics, it avoids some aspects of the character's portrayal dating back to the 1970s that "could feel a little stereotypical."

For Liu, it's surely a bit surreal debuting as the character after tweeting at Marvel calling for an Asian superhero all the way back in 2014 — only to himself become the very hero he was looking for. Besides, today just so happens to be Liu's birthday. As far as birthday presents go, this was surely a pretty good one, and Liu could hardly contain his excitement as he tweeted, "THIS IS THE BEST BIRTHDAY EVER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"

Shang-Chi and the Legend of the Ten Rings is set to hit theaters in September. Brendan Morrow