Everything You Want To Know About COVID-19 Vaccines The U.S. has been vaccinating people against COVID-19 for a little over a month. While there have been plenty of hiccups, over 20 million people in the country have received at least one dose of either the Pfizer-BioNTech or the Moderna shots. For the past few weeks, Science Friday has been collecting your questions about the COVID-19 vaccines on the SciFri VoxPop App—and we heard from a lot of listeners. The questions and concerns ranged from if people with antibodies should get vaccinated to if the vaccines are safe for pregnant women. Joining Ira to tackle these listener questions is Benhur Lee, professor of microbiology at the Icahn School of Medicine at Mount Sinai in New York City.   How Scientists Unravel The Mysteries Of The Placenta Here’s a fun fact for your next virtual trivia night: What’s the only organ that we can grow temporarily, and discard after it’s been used? The answer: the placenta. It may be a disposable organ, but scientists have a tricky time studying it: You can’t poke at it, sample it, or pull it out to see how it works while it’s doing its job of growing a human baby. In an effort to understand how this squishy, purplish, pancake-shaped organ performs some of its most important functions, researchers have had to turn to creative techniques. Ann-Charlotte Iverson, professor at the Norwegian University of Science and Technology, and Nicholas Heaton, assistant professor at Duke University, join Science Friday to discuss how the placenta protects a fetus from viral infection and inflammation, and what happens when something goes wrong.   A New President, A New Climate Policy When President Biden was running for office, he campaigned on re-entering the Paris climate accords his first day in the White House. He followed through shortly after being sworn in. But in the week that followed, the new President has also taken additional steps focused on reducing carbon emissions and adapting to the changing climate—like a push to move the government vehicle fleet to electric vehicles, establishing a White House Office of Domestic Climate Policy, and pausing oil and gas exploration leases on federal lands. Sophie Bushwick, technology editor at Scientific American, joins Ira to talk about Biden’s climate moves, as well as other stories from the week in science, including a study of global ice loss, a halt to Merck’s COVID-19 vaccine trials, and a question about the aquatic habits of an ancient dinosaur.