Testing of the COVID-19 vaccine, which uses tobacco leaves, initially began in 2020, with the next round of human trials due in the spring.

The low-nicotine Australian tobacco variety is different to the kind used in cigarettes.

Researchers say the speed at which it grows means it can be turned from a seed into a vaccine within a month and the technology is highly adaptable.

"It takes only 10 days for us to produce a prototype and... no more than three weeks to test whether that prototype works or not," assistant professor Dr Suthira Taychakhoonavudh, chief executive of Baiya Phytopharm, told Sky News.

"For example, right now, we are already working on the Omicron strains. We have the prototype and we're testing it right now."

The harvested leaves are used as a host to produce proteins which mimic the COVID-19 virus.

The leaves are blended and the protein is extracted.

When the resulting vaccine is injected into humans it stimulates antibodies which our bodies can use to fight the real virus in the future.

The earliest the vaccine would be cleared for use is late 2022.

Even though other COVID-19 vaccinations are already available, developers say it's important to continue the project for future health security.

"COVID-19 is not going to be the last one, right? You're going to have so many emerging diseases and if we can develop the vaccine ourselves, then we don't have to rely on vaccines from other countries," explained co-founder and chief technology officer Dr Waranyoo Phoolcharoen.

The team say the benefit of the tobacco plants, particularly for low-income countries, is that you can grow them almost anywhere in the world at low cost.

The clinical trials are still ongoing so growing conditions in the Bangkok lab are tightly controlled and monitored, with researchers dressed in protective clothing.

The facility at Chulalongkorn University is the first of its kind in Asia making tobacco-based vaccines for human use.

If successful, they hope to produce 60 million doses a year and, once perfected, the tobacco-based technology is versatile.

"We can use it to produce other drugs. So we can use it to produce anti-cancer, anti-rabies, anti-venoms and those we will focus on more. [For example] Tropical diseases that normally multinational pharmaceutical companies might not be interested in," said Dr Taychakhoonavudh.

In early December, Canadian drug developer Medicago said its plant-based COVID-19 vaccine candidate, enhanced by GlaxoSmithKline's booster, was 75.3% effective against the Delta variant of the virus in a late-stage study.

They said the vaccine's overall efficacy rate against all variants of the coronavirus was 71%, except Omicron, which was not in circulation when the study was underway.

The Thai project still has two more sets of trials to complete and needs regulator approval before it can be used by the public but the scientists say plant-based vaccines offer a growing number of opportunities for countries like Thailand to develop their own weapons to fight deadly diseases.