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
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…