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You can keep building your STEM skills at Brilliant.org/SciShow with 20% off an annual premium subscription! As we humans try to reduce our impact on the planet, all sorts of products are going plant-based, from burgers and meatballs to shoes.

And now, even vaccines are following suit. Scientists are developing vaccines that can be grown in plants instead of animal cells. In 2006, the first plant-based vaccine was approved in the U.

S. for chickens. And while this technology is still not widely used, it gives us an idea where vaccines might be headed, and why we might want them to go the way of the Beyond Burger. Now, traditionally, vaccines are grown in eggs or animal cell cultures.

That’s because, to produce a vaccine the traditional way, you need a bunch of copies of a virus. And if you inject a virus into animal cells, it will grow and replicate itself. For instance, one way to manufacture the flu vaccine is in the cells of fertilized chicken eggs.

Other vaccines, like the ones for polio and measles, are grown in cultures of animal cells that have been propagated in labs. Once these viruses are grown, they’re extracted and then typically weakened or killed before getting injected into people, or chickens, to give them immunity. But this isn’t the only way to do things.

It’s also possible to grow vaccines in plants. It just works a little differently. Instead of growing a whole virus in the plant’s cells, genetic engineers transfer certain genes from the virus into the plant’s genome.

Those genes make viral proteins that appear in the plant’s tissues or seeds. And then just eating the plant could provide immunity. No need for a shot.

For example, scientists have successfully grown a common protein found in the flu virus in a tiny flowering plant called duckweed. This means that an animal like a chicken could eat this duckweed and boom—vaccinate itself against the flu. But even if the plant that grew the vaccine can’t be eaten directly, the viral proteins could be extracted from the plant and mixed with foods.

And again, the vaccine could be eaten. Which would just be so much more convenient than having to vaccinate a population with shots. These vaccines come with other benefits, too.

Like, since plant-based vaccines are produced in plant tissues, they can be stored at room temperature, like the seeds or dried leaves of any other plant. That’s way easier than handling other vaccines, which typically have to be transported and stored at precise temperatures, sometimes well below freezing. Plant-based vaccines are also quicker and cheaper to manufacture.

Because when you’re making a vaccine in animal cells, you have to go to great lengths to make sure they don’t get contaminated with pathogens, but that’s typically not a worry when you’re making a vaccine in plants. So you might be wondering why anyone is still getting shots instead of just popping an edible, plant-based vaccine. And the answer is that, for now, scientists still don’t know how to make oral vaccines as effective as injected ones.

For one, it’s a lot easier for the viral proteins in a vaccine to survive in the bloodstream than in an organism’s stomach. Your digestive system is in fact very good at breaking down proteins. That’s kind of the point of eating.

So the challenge is getting these viral proteins to survive long enough for the body to identify them and mount an immune response, and remember the experience later if it encounters the real pathogen. And scientists haven’t completely cracked that yet. There's also a problem called oral tolerance.

In mammals in particular, the gut sometimes ignores viral proteins rather than mount a massive inflammatory response. This can be helpful, because mammals often encounter harmless viruses in their food that they don’t need to waste energy fighting off. But when the point of a vaccine is specifically to introduce the body to an intruder so it can learn to fight it off in the future… oral tolerance can be a problem.

Fortunately, for reasons that aren’t completely understood, oral tolerance isn’t such a big problem among chickens. So, scientists are especially interested in applying these methods to vaccinate chickens against viruses like avian influenza, which can wreak all sorts of havoc. These diseases can kill off chickens and cause huge spikes in the price of eggs and meat.

But on top of that, bird flu can sometimes jump to people, and some strains can be deadly. So, scientists, farmers, and ordinary people have good reasons for wanting to vaccinate chickens en masse, and edible vaccines could be a huge improvement over current methods. I mean, today’s methods typically involve bringing a qualified person out to a farm to individually vaccinate thousands of birds.

If you have 20,000 chickens, that’s 20,000 syringes or eyedroppers, not to mention 20,000 anxious birds. On the other hand, you could toss them some vaccine-spiked plants and they could vaccinate themselves while they eat. This technology still has a ways to go, but plant-based vaccines may play a more important role in our lives in the future.

Halting the spread of bird flu and other poultry viruses depends on getting vaccines made, transported, and distributed fast. And it’s starting to look like plant-based oral vaccines may be a good way to do that. Vaccine development and distribution is an ongoing problem that a lot of people are trying to solve.

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