Three days after the first presidential debate last week, Trump announced he had tested positive for Covid-19, raising questions about whether he might have exposed Biden when they met in Cleveland. The two candidates did not shake hands and were on opposite sides of the stage, and Biden has consistently tested negative, including on Tuesday.

Guidelines from the Centers for Disease Control and Prevention say that because of Pence’s proximity to the president and exposure to the virus, he should quarantine for another week. However, with Pence testing negative for the virus, his advisers say that not only will he go forward with the in-person face-off, but that any dividers are not medically necessary because the candidates will be 12 feet apart.

Plexiglass dividers are one tool to prevent transmission of the virus, but are typically used in combination with other measures, like maintaining a 6-foot social distance and requiring masks. The demand for barriers in the vice presidential debate was among a larger list of Biden campaign conditions, which included testing, face coverings and a larger distance between the candidates.

The debate over the debate is bound to have an effect beyond Wednesday, since the vice presidential debate will likely serve as a trial run for the final two match-ups between Trump and Biden in the run-up to Election Day. But even if plexiglass barriers are used in the remaining debates, their protective benefits are far from proven when it comes to the coronavirus.

Dr. Saskia Popescu, an infectious disease epidemiologist at the University of Arizona, said it wasn’t entirely clear how effective plexiglass barriers are at preventing the transmission of Covid-19. The dividers are not “a substitute for any of the efforts we know work,” she said.

“Ultimately, this debate should be virtual as Vice President Pence should be quarantining,” Popescu said. “If that’s not an option, every and all safety measures should be taken, which should include masks, distancing, avoiding any additional people in the space who don’t need to be, trying to do it outdoors, cleaning.”

“Plexiglass dividers,” she added, “can be helpful against larger droplets, but there are concerns for efficacy against smaller aerosols, which should reinforce the use of masks as source control.”

Nonetheless, such dividers — often used in grocery stores, classrooms and gyms — have gained popularity in political debates over the past week. In South Carolina, Democrat Jamie Harrison brought his own plexiglass shield to debate Sen. Lindsay Graham (R-N.C.). Harrison addressed the divider early in the debate, saying it served as a safety measure and a symbol of how he takes the virus seriously.

“We shouldn’t blame anybody for the inception of this disease,” Harrison said. “Where blame should come is how we handled this disease, whether or not we took it seriously. Tonight I am taking it seriously. That’s why I put this plexiglass up. It’s not just about me, it’s about the people in my life that I have to take care of.”

In the race between incumbent Sen. Ed Markey (D-Mass.) and his Republican challenger, Kevin O’Connor, Trump’s illness led to a last-minute change to the format of the debate. Moderators Jim Braude and Margery Eagan, hosts on the public radio station WGBH, were separated by plexiglass.

The candidates took things a step further and debated from separate studios, which Markey welcomed but O’Connor took issue with. The resulting split-screen was at times reminiscent of a heated cable news segment, with some crosstalk and interruptions. But it also kept the candidates at a safe social distance.

“Our view is the world changed on Friday and we tried to change with it,” Braude said, referring to the day Trump was diagnosed with Covid-19. “Our goal was to make things as safe for both of you and us as possible.”

After his own socially distant showdown, Markey said he thought Trump and Biden should continue their debates ahead of the November election. If Trump is still ill or otherwise tests positive for the virus, Markey said, the pair should find a creative way to debate safely.

“I think that conditions can be constructed that would make it safe for both of them to debate,” Markey said. “If there’s another alternative that can be constructed, even if the president does not test negative, such as we had tonight, then yes, these debates should go on.”