This COVID-19 Vaccine Is the First Plant-based Vaccine for Humans

Although there are multiple COVID-19 vaccines on the market, a vaccine developed in collaboration with Canadian biotechnology company Medicago and pharmaceutical company GlaxoSmithKline has one unique quality: It's plant-based.

This two-dose COVID-19 vaccine is the first plant-based vaccine authorized for use in humans, according to this study from June 2022 in The New England Journal of Medicine. Not only that, but results from the study show that the vaccine was 78.8% effective at protecting against moderate-to-severe infections of 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 immunization, "plant-based" simply means researchers recruited plants to produce part of the vaccine, Brian Ward, MD, Medical Officer at Medicago, said. The exact plant they use is called Nicotiana Benthmiana, a close relative of tobacco, according to a June 2022 study in The New England Journal of Medicine.

What makes this plant so appealing is its susceptibility to infection from a variety of pathogens, according to an article from 2015 in Plant Physiology. 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 World Health Organization (WHO). When our bodies have a new antigen, they make antibodies. Together, the antibodies and antigens fight off pathogens (viruses, bacteria, parasites, or fungi).

How Is the Plant-based COVID-19 Vaccine Different?

In the case of COVID-19, the spike protein acts as the antigen, according to the Centers for Disease Control and Prevention (CDC). That's the area the virus vaccines try to replicate, said Amesh Adalja, MD, an infectious disease physician and senior scholar at the Johns Hopkins School of Medicine. However, each vaccine has its own unique approach to doing so, Dr. Adalja said.

For example, some—like the Johnson & Johnson vaccine—use a modified virus to introduce the spike protein to our cells, according to the CDC. 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, according to the CDC.

Medicago's vaccine method is different—it starts by introducing the genetic code for making the spike protein into plants, not humans, according to the June 2022 study in The New England Journal of Medicine. 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 said.

Using Virus-like Particles

All of these spike proteins then start clumping together to form molecules that look like viruses, according to the same June 2022 study. These molecules, called virus-like particles (VLPs), form in the leaves of the plant and are the antigen in Medicago's vaccine.

The spike protein portion of the Coronavirus genome is introduced into the plant so that the plant's cellular machinery can synthesize multiple spike proteins, according to an article from February 2022 in Cellular and Molecular Immunology. The spike proteins form together, three at a time, to form trimers. These proteins travel to the plant's cell membrane, spontaneously assemble, and use a piece of the membrane to 'bud off' as a viral-like particle (VLP).

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

Adding an Adjuvant

Other than VLPs, Medicago's vaccine has one other key component: an adjuvant made by GlaxoSmithKline, according to the June 2022 study. Adjuvants are ingredients found in some, but not all, vaccines, which generate a more robust immune response, according to the CDC. Whereas VLPs are the intruders the immune system attacks, adjuvants are like concerned neighbors, alerting the body's defense 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 explained. "[This] allows more vaccine doses to be produced and, therefore, contributes to protecting more people."

Dr. Ward said 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, Dr. Ward said. 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 said, noting this may be one reason why the vaccine performed so well in a 100% variant environment.

How Effective Is It?

According to the June 2022 study, Medicago's plant-based vaccine had an overall efficacy rate of 69.5%, which included 24,141 participants across 6 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 said.

Does the Vaccine Cause Side Effects?

The plant-based vaccine was well-tolerated in trial participants, and no serious adverse events have been reported in the vaccine group, according to the same June 2022 study. However, like most vaccines, it did appear to cause some side effects—mostly mild to moderate symptoms such as:

• Fever
• Muscle aches
• Fatigue
• Headache

However, these side effects are just a result of the immune system doing its job: "An annoyed immune system is an alert immune system," Dr. Ward said. "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."

What Are the Benefits of Plant-based Vaccines?

Plant-based vaccines may have many benefits. First and foremost, they provide people with another vaccine option against COVID-19—and it's always good to have various options when battling a pandemic, Dr. Ward said. That's because certain vaccines may be easier to transport or administer in specific locations, Dr. Adalja added.

Stored at Refrigerator Temperature

For example, Pfizer's vaccine has to be stored at temperatures between -130 and -76 F, according to the CDC. "It's difficult to keep vaccines that cold in many parts of the world or in rural areas," Dr. Adalja said. In contrast, Medicago's plant-based vaccine can be stored at temperatures found in most refrigerators, according to the June 2022 study.

More Can Be Produced

Additionally, plant-based vaccines can be produced in greater amounts, according to the 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 said.

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, as Dr. Ward pointed 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 built in Quebec City, Dr. Ward said.

"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 [the COVID-19] outbreak," Dr. Ward said.

Cost Effective

The WHO also said plant-based vaccines are cheaper to produce. Medicago declined to disclose the cost of its product. Instead, the company stated it is priced fairly and in line with other vaccines.

Adaptable

Mostly though, plant-based vaccines are beneficial simply because they're a new technology, meaning they 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 said.

When Should You Get the Vaccine?

Get the first vaccine available to you—whether it's the plant-based vaccine, the single shot from Johnson & Johnson, or either of the two-dose regimens made by Pfizer-BioNTech or Moderna. And if you were considered fully vaccinated at least six months ago, you should get a COVID-19 booster shot (if you haven't already) per the CDC's recommendations.

A Quick Review

The first plant-based vaccine was created in response to the COVID-19 pandemic. This new technology is efficient, reliable, and works similarly to other vaccines. There are countless benefits to plant-based vaccines. But regardless, you should consider getting a vaccine to protect yourself from COVID-19.