Illustrations: Cleo Peng

The Bold Attempt to Grow a Covid-19 Vaccine in Plants

Scientists are finding that fields of crops might be easier to manage than vats of cells

Leslie Nemo
Future Human
Published in
8 min readOct 1, 2020

Most pharmaceutical companies currently pursuing a coronavirus vaccine are doing so with bioreactors — large, metal, temperature-controlled tanks holding millions of cells that are engineered to pump out viral bits that can protect people from Covid-19. But a few companies designing these vaccines are approaching their production differently. When they generate vaccine candidates, their scientists will tend to a bed of plants.

If all goes to plan, each rounded leaf sprouting from the bright green crops will fill up with proteins that elicit Covid-19 immunity, once extracted and packaged into a shot. These so-called plant-based vaccines are the product of 30 years of work from a handful of scientists determined to turn crops into tiny pharmaceutical factories. People outside this small circle of expertise used to wonder whether the protein-building equipment in plants could also assemble human virus particles.

“People had questions around, well, can the plant machinery really make the virus? Because the virus doesn’t normally replicate there, is the machinery adapted to do that?” Matthew Miller, PhD, an infectious disease researcher at McMaster University in Canada, asked Future Human. “Now we’re understanding that, by and large, it is.”

Canada-based Medicago and the U.S. company Kentucky BioProcessing each hope to develop a vaccine against SARS-CoV-2, the virus that causes Covid-19, using this technique. If either vaccine is proven safe and effective, it could become the first plant-based variety ever approved by the U.S. Food and Drug Administration. Medicago is already moving through phase 1 trials. Compared to traditional manufacturing methods, plant-powered vaccine production promises to be efficient and relatively worry-free. And, as concerns mount about the ability of manufacturers to meet international vaccine demands during a pandemic, its allure skyrockets. Those pursuing the greenhouse-based vaccine technique are now working quickly to overcome the final barriers to their success.

“Is the machinery adapted to do that? Now we’re understanding…