New self-amplifying RNA vaccine safe in humans, boasts advantages

British researchers have developed a new type of RNA vaccine for COVID-19 that requires such a low dosage that one liter of the material could produce 1 million doses.

The jab, which was recently found to be safe in humans, uses self-amplifying genetic material, or saRNA, and works in a similar way to the highly effective mRNA COVID-19 vaccine, while utilizing far fewer resources.

The mRNA vaccines from Moderna and Pfizer use 100 micrograms and 30 micrograms of genetic material respectively in each dose, whereas Imperial College London scientists believe that the ideal dosage for their saRNA vaccine lies between 0.1 and 10 micrograms.

Such a low dosage means that the treatment would be cheaper and easier to mass produce. Robin Shattock, who leads Imperial College London's COVID-19 vaccine project, says that the vaccine could be used to combat emerging variants of the novel coronavirus, and the technology has the potential for application against other diseases, including Ebola, rabies, malaria, and types of cancers.

"The approach is emerging as one of the great scientific advances of the pandemic, with the ultra-low dose offering three key advantages. The first is the potential to manufacture a huge amount－one liter of reaction material can produce up to one million doses," Shattock said.

He said that another advantage is that a lower dose reduces the likelihood of side effects.

"Finally, a low-dose vaccine opens up the possibility of combining the COVID-19 vaccine with other vaccines," he added. "We may now need annual vaccines against COVID-19, and a lower dose makes combination with other vaccines, such as the flu vaccine, more feasible."

In a recently released preprint study in The Lancet, the treatment was shown to be safe with no serious side effects in early trials involving 192 participants. Researchers said that the vaccine induced a good immune response among some people, while others had a limited response. The team is now modifying the vaccine in order to enhance its efficacy.

"Global demand for COVID-19 vaccines will remain high in the coming decade, given the emergence of lethal SARS-CoV-2 escape-variants, and expected requirement for booster vaccination," Shattock said. "We have shown the saRNA technology is safe and can generate an immune response. We are now refining the Imperial saRNA platform to develop vaccines for a variety of other infectious diseases."

The saRNA vaccine instructs the immune system to produce antibodies against the virus, much in the same way as the mRNA vaccine. The key difference is, when delivered to the injection site, saRNA also instructs the body to make copies of itself, so-called self-amplification, meaning far less of the material is needed in the initial dosage.

Low-dosage vaccines are particularly advantageous for inoculation campaigns that require billions of doses, including those for COVID-19 and malaria. In February this year, Yale University researchers filed a patent application for a saRNA malaria vaccine which has shown promising results in animal testing. If the vaccine is successful, it could help solve one of the largest public health problems in the world; according to the World Health Organization, there were 229 million malaria infections and 409,000 deaths in 2019.