JOHN DANKOSKY: This is Science Friday. I’m John Dankosky, Ira Flatow is away. Later this hour we’ll take a look at the water crisis in Jackson, Mississippi, and we’ll dive into the reproductive lives of sharks.

But first, President Biden made his first prime-time address last night, just a day after he signed the $1.9 trillion American Rescue Plan. In his speech, Biden called for all adults to be eligible for the COVID-19 vaccine earlier than expected.

PRESIDENT BIDEN: I’m announcing that I will direct all states, tribes, and territories to make all adults– people 18 and over– eligible to be vaccinated no later than May 1. Let me say that again. All adult Americans will be eligible to get a vaccine no later than May 1.

JOHN DANKOSKY: Biden stressed that that doesn’t mean everyone in the country will have the shots by then, but he wants everyone to be able to get in line. Sophie Bushwick is here to fill us in on Biden’s plan, new CDC guidelines, and other news of the week. She’s the technology editor at Scientific American and she’s based out of New York. Sophie, welcome back to Science Friday. Thanks so much for being here.

SOPHIE BUSHWICK: Thank you.

JOHN DANKOSKY: So how does President Biden plan to speed up this vaccination process?

SOPHIE BUSHWICK: President Biden has been giving estimates of how much vaccination would be available since the beginning of his term. He pledged to have 100 million vaccinations in the first 100 days and is on track to achieve that goal. So the latest goal seems to be that all adult Americans will be eligible to receive their vaccines by May 1st. And he has said previously that by May there will be enough vaccines in existence having been produced for every American adult who wants one.

JOHN DANKOSKY: Given the fact that states are vaccinating at different rates right now, they’ve all got different priority groups, does this seem attainable?

SOPHIE BUSHWICK: Well, I think changing the eligibility might be attainable, but I think the speed with which those shots will get into arms is going to depend on a lot of factors. Like you said, the vaccination plans vary from state to state and the infrastructure in place to give people vaccines also differs. So I think cautious optimism is probably good. I don’t think people should expect that, as of May 1st they’ll be able to have an appointment to get their shot. But I think that we can hope that very soon afterwards people will be able to start making those appointments.

JOHN DANKOSKY: Anything else in his speech about the pandemic that stuck out to you?

SOPHIE BUSHWICK: The idea that Americans might be able to celebrate the 4th of July together in groups, in larger gatherings than we’ve been having for over a year is a pretty inspiring goal. Again, that’s a goal. I can’t read the future. But it is definitely something to aspire to.

JOHN DANKOSKY: All right, we’ll make those barbecue plans, I suppose. Also this week, the Centers for Disease Control and Prevention released guidelines for people who have been fully vaccinated. What are those guidelines proposed?

SOPHIE BUSHWICK: So, those guidelines suggest that people who have been vaccinated have more freedom than they might have had since the beginning of the pandemic but that they shouldn’t throw all caution to the winds yet. So people who have been vaccinated can gather indoors with other vaccinated people without masks and without maintaining social distancing.

Also, the CDC suggests that if you’ve been vaccinated you can meet with unvaccinated people as long as those people are from a single household and everyone in that household is at low risk of severe COVID-19. So you might be able to gather with a single family, grandparents might be able to visit their grandchildren, but they’re not necessarily saying, go to a giant party filled with unvaccinated friends.

And the other thing is that they still suggest, for things like travel, that you avoid unnecessary travel. They still suggest that you avoid large groups, and those types of precautions, and that you wear a mask and maintain distancing with people who are unvaccinated still. So it’s not complete normalcy but it’s starting to move in that direction.

JOHN DANKOSKY: Do we still know any more about whether vaccinated people can transmit the virus?

SOPHIE BUSHWICK: There is some preliminary data that suggests that transmission goes down a lot with people who have been vaccinated but that is still preliminary. And there are even differences from different epidemiologists and infectious disease specialists about what it’s safe to do. Some have said go ahead, and it should be OK to eat in restaurants indoors and to travel as long as you’re wearing a mask and trying to maintain distancing. While others have said, well, don’t jump into it yet, let’s give it a little bit more time and get more results. So there are different levels of caution depending on who you speak with.

JOHN DANKOSKY: There was a study out by the CDC looking at the effectiveness of these mask mandates. What did it find?

SOPHIE BUSHWICK: The CDC found that in states and counties that had mask mandates the rate of transmission of COVID-19 and the rate of deaths from COVID-19 went down starting about 20 days after the mandate was put in place.

JOHN DANKOSKY: So that means that mask mandates still work. There’s been a lot of push back, though, on some of what the CDC has said. I know people in the restaurant industry are worried that there’s a message getting out there that gathering in restaurants might still be a cause of spread?

SOPHIE BUSHWICK: Right, so in the same report where the CDC looked at mask mandates they also looked at indoor dining. And they found that in counties that had opened their indoor dining, they saw an increase in the rate of transmission of COVID-19 about 40 days after the restaurants were allowed to open. And then another 20 days after that, an increase in the death rate. And so their findings indicate that indoor dining could be a cause of spread.

And yes, the restaurant industry has pushed back against that conclusion. This is sort of more of the same of what we’ve seen throughout the pandemic, where the CDC and some other public health professionals have encouraged people to be more cautious and to lean towards not opening things like indoor dining and towards having mask mandates, while often, on the other side, businesses have kind of pushed back through worries that they are going to suffer economically from conclusions like that.

JOHN DANKOSKY: So let’s move on to some other non-COVID science news this week, because we have a lot of it. Your next story looks at smart devices that are being used to monitor health. A team of researchers looking at kind of hacking smart speakers for this? Tell us more.

SOPHIE BUSHWICK: Right, so your smart speaker does a lot for you, maybe it can measure your heart rate as well. Just the way that bats use echolocation to notice where things are in space, this study rests on similar physics rules. They have a smart speaker release an inaudible sound, and when that sound bounces back to the speaker it can detect objects nearby. And the idea is that because there’s multiple microphones on a speaker pointing around, it can actually sense small changes, including the changes caused by a heartbeat on a person’s chest.

So for this study, they had people sit just a couple of feet from a smart speaker and the smart speaker could detect their heart rate. And even if there was an irregular heart rate the smart speaker was also capable of detecting that. Which is pretty exciting because irregular heart rate can cause a stroke, it can cause other physical problems, so being able to detect it early without having someone required to go into a doctor’s office is a pretty interesting application.

JOHN DANKOSKY: So that is pretty cool. As with anything with smart speakers, a little bit scary, but these are early days, right? This isn’t going to start happening pretty soon?

SOPHIE BUSHWICK: Right. Again, the person had to be sitting in front of the smart speaker, this is a very specific application. But the researchers have suggested that maybe if they continue to develop this line of work you can have the smart speaker monitoring your heart rate while you’re sleeping, maybe it could pick up whether you’ve got some sleep apnea. There have been studies in recent years that use a lot of surveillance for health and they use clues about changes in your environment to see how healthy you are, but also what you’re doing.

So on the one hand, this seems like it could be a privacy disaster if it is implemented in an incautious way. But on the other hand, it does seem to have some implications for monitoring someone’s health without requiring– you don’t have to have anything touching you, don’t have to be in a doctor’s office, so it does have some potential to keep an eye on.

JOHN DANKOSKY: That’s so cool. All right, I want to make sure we have time for this last story. Let’s talk about the headless sea slug. You got to tell us about this, what’s happening with sea slugs losing their heads?

SOPHIE BUSHWICK: Two species of sea slug can completely lose their head. In fact, it seems like they themselves sever their own heads from their bodies and then they regrow an entire body from the neck down.

JOHN DANKOSKY: What? So hold it, they purposely take their own heads off, the head survives and the body survives?

SOPHIE BUSHWICK: That’s right. So the body itself survives for a pretty long time, for weeks, but it does eventually die. The head can survive and also, within a few weeks, it regrows its body, a new body identical to its old one. And then it goes on its merry way.

JOHN DANKOSKY: Well first of all, why would it want to detach its own head? I mean what would be the reason to get rid of a perfectly good body?

SOPHIE BUSHWICK: So, one reason might be to evade predators. We do see other animal species that are able to regrow limbs or tails when they lose them to predators. And the scientists think that in those cases, if a bigger animal bites you or is trying to grab you, the ability to ditch one of your limbs or even ditch your entire body and then regrow it could help your survival. And another possibility is parasites. If a slugs body is just filled with parasites it might say, ugh, this body is so messed up, I need to get a new one. And then it just severs its own head, regrows the body, and it has a fresh, parasite free body to keep going on with.

JOHN DANKOSKY: How long does this process take to regrow an entire body?

SOPHIE BUSHWICK: The body was regrown in about three weeks. But this only seems to work with younger slugs. When the slugs get older, they seem to lose the ability to do this.

JOHN DANKOSKY: As it’s regrowing its body, though, how does it eat? I mean, how does it stay alive? It doesn’t have any way to take in food, right?

SOPHIE BUSHWICK: Now this is really cool, the slug actually steals the parts of plants that allow them to gain energy through photosynthesis. It has the ability to power itself through photosynthesis for the first few days while its wound heals and then researchers think it does eat a little bit to help it gain the energy it needs to regrow that body.

JOHN DANKOSKY: So, OK, this is fascinating. Are there any other animals that we found that are able to do this particular thing, regrow an entire body? And how is it doing this, what allows the slug to regrow in this way?

SOPHIE BUSHWICK: As far as we know, this is the only animal that can regrow its full body. We do know that other animals like starfish can regrow limbs, there’s animals that can ditch their tails, but regrowing the whole body– this is about 80% of its total mass that it’s regrowing– this is the only feat of its kind that we’ve seen. And we think that they’re doing it through stem cells. So stem cells are cells that can become any other type of cell, and the researchers at the moment suggest that that could be the mechanism that they’re using. But they have to study it more to learn exactly what’s going on.

JOHN DANKOSKY: That is so cool. I have to say, though, I saw one of the pictures on your site of the head crawling around the body and it kind of creeped me out.

SOPHIE BUSHWICK: I can’t look at that video clip, my shoulders go right up around my ears. There’s something about the way the head bumps into the body that it used to be attached to and then moves away that just freaks me out.

JOHN DANKOSKY: Yeah, don’t look at that right before you go to bed, that’s all I have to say. That’s all the time we have. Thanks so much, Sophie.

SOPHIE BUSHWICK: Thanks for having me.

JOHN DANKOSKY: Sophie Bushwick is the technology editor at Scientific American.