Although there are already multiple coronavirus vaccines on the market, the latest contender — a vaccine developed in a collaboration between Canadian biotechnology company, Medicago and pharmaceutical company, GlaxoSmithKline—has one unique quality: it’s plant-based.

If approved, the two-dose COVID-19 vaccine would become the first plant-based vaccine authorised for use in humans, according to a statement released by Medicago, a private company held by Japan’s Mitsubishi Tanabe Pharma Corporation and a subsidiary of Big Tobacco giant Philip Morris International. Not only that, but results from its phase 3 trial are promising: it was 71 percent effective at protecting against COVID-19.

Here’s what it means for a vaccine to be plant-based, how plant-based vaccines work, and the potential benefits of this new technology.

What is a plant-based vaccine?

While plant-based vaccines may sound like the latest iteration of veganism, that’s not the case. In fact, when it comes to immunisation, “plant-based” simply means researchers recruited plants to produce part of the vaccine, Brian Ward, MD, Medical Officer at Medicago tells Health. The exact plant researchers use is Nicotiana Benthmiana, a close relative of tobacco.

What makes this plant so appealing is its susceptibility to infection from a variety of pathogens, including COVID-19. This means researchers can use the leafy organism as a vessel for producing antigens, a key component of vaccines. Antigens are the part of viruses (and vaccines) that spur our immune systems into action, according to the National Institute of Allergy and Infectious Diseases.

In the case of COVID, the spike protein acts as the antigen. Therefore, that’s the area of the virus vaccines try to replicate, Amesh Adalja, MD, an infectious disease physician and senior scholar at the John’s Hopkins School of Medicine, tells Health. However, each vaccine has its own unique approach for doing so, he says. For example, some—like Johnson and Johnson/Janssen’s vaccine—use a modified virus to introduce the spike protein to our cells. Others, like the Pfizer-BioNTech and Moderna vaccines, carry a genetic code for the spike protein, which our bodies then make and destroy, kind of like a practice run.

Medicago’s vaccine method is different—it starts by introducing the genetic code for making the spike protein into plants, not humans. This code acts like an instruction manual: the plant cells read it and then use the information to start pumping out spike proteins in surplus, Dr Ward says.

All of these spike proteins then start clumping together in groups of three, which then clump together even more, forming molecules that look like viruses. These molecules—called virus-like particles (VLPs)—form in the leaves of the plant over the course of four days and are the antigen in Medicago’s vaccine.

“These VLPs are very complex molecular structures that look like a virus — same size, same organisation — except they have no genetic information inside so they’re non-infectious,” Dr Ward explains. Once injected into the body, these “pseudo viruses” trick the immune system into action, Dr Adalja says. But, unlike actual viruses, they cannot replicate or make us sick.

Other than VLPs, Medicago’s vaccine has one other key component: an adjuvant made by GlaxoSmithKline. Adjuvants are ingredients found in some, but not all, vaccines, which generate a more robust immune response, according to the Centers for Disease Control and Prevention (CDC). Whereas VLPs are the intruders the immune system attacks, adjuvants are like concerned neighbours, alerting the body’s defence system that it’s been breached.

“Use of an adjuvant can be of particular importance in a pandemic situation as it may boost the immune response and reduce the amount of antigen required per dose,” Dr Ward explains. “[This] allows more vaccine doses to be produced and, therefore, contributing to protect more people.”

How did the new-technology perform in trials?

plant based vaccine
Image Credit: Mufid Majnun/Unsplash

Medicago’s plant-based vaccine had an overall efficacy rate of 71 percent during phase 3 trials, which included 24,000 adult participants across six countries.

“That’s against any symptomatic COVID, so if someone developed a single symptom compatible with the disease, we would test them. If it was positive, we counted that as a case,” Dr Ward says, noting they will soon be able to determine if the vaccine prevented people from getting asymptomatic COVID, too.

It’s impossible to compare the efficacy rate of this vaccine to others on the market as each was tested in unique circumstances. Even so, Dr Ward says they do know that the plant-based vaccine produces a stronger immune response than other types of vaccines, thanks to VLPs.

According to Dr Ward, VLPs maintain their structure as they travel through our blood—think of them like flowers drifting in a rapidly moving stream, he says. In comparison, other vaccines use singular spike proteins, which are like individual flower petals that quickly disperse in our bloodstream.

“[Since] VLPs get delivered as a bundle — and a bundle looks more like a virus to the immune system — the immune system reacts more strongly,” Dr Ward says, noting this may be one reason why the vaccine performed so well in a 100 percent variant environment. In fact, the plant-based vaccine was 75.3 percent effective against the now dominant Delta strain and almost 89 percent effective against the Gamma strain.

“That’s pretty cool because Gamma is known to be an immunoinvasive variant, meaning it’s able to infect people who were previously vaccinated,” Dr Ward says. “So we’re pretty excited about the results.”

Currently, there is no data on how the plant-based vaccine performs against Omicron, since the variant wasn’t circulating at the time of the phase 3 trial.

However, Dr Adalja says it’s way too early to tell if one vaccine approach is better than another in combatting COVID: “We don’t have enough data to say that.”

Does the vaccine cause side effects?

So far, the plant-based vaccine has been well-tolerated in trial participants, and no serious adverse events have been reported in the vaccine group, according to Medicago’s press release.

However, like most vaccines, it did appear to cause some side effects—mostly mild to moderate symptoms that resolved within 1-3 days.

plant based vaccine
Image Credit: Adrian Swancar/Unsplash

The most common side effect was a sore arm, Dr Ward says, and between 40 percent and 50 percent of participants reported some sort of systemic reaction like fatigue, muscle aches, or headaches. Less than 10 percent of subjects experienced a mild fever.

However, these side effects are just a result of our immune system doing its job: “An annoyed immune system is an alert immune system,” Dr Ward says. “It basically sends a signal to the rest of the body [that] something is going on here that we don’t like…and stimulates a strong immune response.”

When will the vaccine be made available?

Right now, the plant-based vaccine is not available, but Medicago plans on seeking approval from Health Canada “imminently,” according to their press release.

While Medicago did not disclose exactly how much of the vaccine they are able to produce, Dr Ward says they are scaling their production capacity and “are committed to fulfilling our order with the Government of Canada.”

While the company hasn’t announced plans for when it might seek approval from the US Food and Drug Administration (FDA), the vaccine has already been granted Fast Track Authorization in America, per reporting from VeryWell Health. This means once Medicago applies for authorisation, the process will be expedited, according to the FDA’s website.

In the meantime, the best way to protect yourself against COVID is to get inoculated with one of the vaccines already on the market, Dr Adalja says, stressing that people should not wait for approval of the plant-based vaccine.

Instead, get the first vaccine available to you, whether it’s the single shot from Johnson and Johnson or either of the two-dose regimens made by Pfizer-BioNTech or Moderna. Meanwhile, those who were considered fully vaccinated at least six months ago should get their COVID booster shot, per the CDC’s recommendations.

What are the benefits of plant-based vaccines?

If approved, plant-based vaccines may have many benefits. First and foremost, they would provide people with another vaccine option against COVID—and it’s always good to have a variety of options when battling a pandemic, Dr Ward says. That’s because certain vaccines may be easier to transport or administer in specific locations, Dr Adalja adds.

For example, Pfizer‘s vaccine has to be stored at temperatures between -25°C to -15°C, according to their website. “It’s difficult to keep vaccines that cold in many parts of the world or in rural areas,” Dr Adalja says. In contrast, Medicago’s plant-based vaccine can be stored at the same temperatures found in most refrigerators, per the press release.

Additionally, plant-based vaccines can be produced in greater amounts, according to the World Health Organization (WHO). That’s because other vaccines, which use yeast, insect, or mammalian cells, have to be stored in large glass containers called bioreactors: “Our bioreactors are, in fact, just cute little plants,” Dr Ward says.

One benefit of using plants as bioreactors is that they can thrive in a greenhouse with very few materials such as light, water, and some sort of substrate to grow in, Dr Ward points out. Greenhouses also mean the vaccines can be produced on both very small scales, like for a specific region or state, or on very-large scales, like the global facility Medicago is currently building in Quebec City, Dr Ward says.

“So, potentially over the long-term, this might be a very attractive platform to have dispersed vaccine manufacturing capacity, which has been such a problem during this outbreak,” Dr Ward says.

The WHO also says plant-based vaccines are cheaper to produce.

Medicago declined to disclose the cost of their product. Instead, the company stated it is priced fairly and in-line with other vaccines.

Mostly though, plant-based vaccines are beneficial simply because they’re a new technology, meaning it can be adapted to other vaccine candidates in the future: “Irrespective of whether a COVID vaccine is successful using this platform, the technology is important for advancing vaccines in general,” Dr Adalja says.

This story first appeared on

(Main and Feature Image Credit: Getty Images)

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