World's first plant-based Covid vaccine Medicago could be approved after trial in Aberdeen

More than 24,000 participants in Canada, Brazil, Mexico, Argentina, the US and UK are taking part in the study, including 55 in Aberdeen, where Dr Roy Soiza, a consultant physician specialising in geriatric medicine, was the lead investigator.

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Dr Soiza said: "This is a completely different type of vaccine so that in itself is quite exciting.

"The ability to use plants to produce vaccines is only a few year old, but one of the advantages is that it can produce quite large amounts of vaccine in a relatively short space of time.

"So for example if there is a new variant of concern - which of course there happens to be now - it would be possible to change the plant model and scale up production in a short space of time, maybe three to four weeks, which is a lot shorter than other types of production.

"I know they are planning to produce a second generation of their own vaccine for Omicron and the other variants which are more prevalent now."

Dr Roy Soiza (inset) led the Aberdeen arm of the clinical trial, which had 55 participants

The technique, developed by Quebec-based pharmaceutical firm Medicago, uses Nicotiana benthamiana plants as "bioreactors" which are first submerged in liquid saturated with bacteria containing a synthesised version of the virus code.

These bacteria are then absorbed into the plant cells and the plants transferred to a greenhouse where, after around four days, they begin to release virus-like particles which can trick the body's immune system into mounting a defence without actually exposing it to an infectious pathogen.

These VLPs are produced rapidly and in large quantities by the plants, which are harvested and blended into a solution to create the pure vaccine.

Dr Soiza said: "Quite why this plant [produces VLPs], nobody knows, but it can be manipulated to express whatever protein you need on its surface.

"For this particular vaccine it's the SARS-Cov-2 spike protein on the surface of the virus-like particle."

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As well as offering a means of producing large amounts of vaccine quickly and comparatively cheaply which can be adapted as the Covid spike protein evolves - the Omicron variant has 30 mutations compared to the original Wuhan strain - plant-based vaccines are expected to be more appealing to some vaccine hesitant individuals who perceive them as more natural or who worry about use of eggs or animal-derived substances in development.

"It was noticeable that this idea of it being a plant-based vaccine was appealing to a number of our volunteers for various reasons," said Dr Soiza.

"Some are vegans, some prefer plants on environmental grounds."

Phase Two clinical trials showed that participants given two doses of the Medicago vaccine 21 days apart developed a strong antibody response - around 10 times higher than those seen in people recovered from Covid - and the Phase Three stage also showed protection of around 88% against infections caused by the Gamma variant common in Brazil.

No serious adverse events were reported and mild side effects were also rare, with fewer than 10% of participants experiencing fever after the second dose.

Medicago, which previously developed a plant-based swine flu vaccine, is now seeking immediate approval from Canadian regulators and is also filing applications for use with UK and US regulators and the World Health Organisation.

The vaccine does not have to be frozen and can be kept refrigerated at 2-8°C, making a potential candidate for use in the developing world.

Takashi Nagao, CEO and President of Medicago, said: “This is an incredible moment for Medicago and for novel vaccine platforms. The results of our clinical trials show the power of plant-based vaccine manufacturing technology.

"If approved, we will be contributing to the world’s fight against the COVID-19 pandemic with the world’s first plantbased vaccine for use in humans.”

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Heather Morgan, a 37-year-old university lecturer who lives near Stonehaven in Aberdeenshire, is among those who took part in the Scottish arm of the trial after seeing advert in April 2020 seeking volunteers aged 18 to 40.

By the time the trial began in May this year, however, the UK's vaccination drive was well advanced - making recruiting and retaining participants increasingly challenging.

However, Ms Morgan said she wanted to support an "alternative approach" and is determined to stick with the trial in spite of rising Covid rates and the emergence of the Omicron variant.

She will not find out until next year whether she received the placebo or the vaccine, but has so far never tested positive for Covid.

She said: "I just felt a sense of responsibility that I should take part because I was eligible and I was thinking at the time that we're going to need more and different types of vaccines and it just seemed that supporting an alternative approach was quite important.

Heather Morgan (inset) is one of the Aberdeen-based trial participants

"I actually had a bit of a wobble around August when everything was opening up again and I didn't know whether or not I should be doing stuff, but I do daily lateral flow tests and I've been away on holiday with friends, I've been into work, I've gone into cafes and pubs, and done all those things according to the regulations.

"I'm not saying it totally reassures me, but I do want to stay in the trial."