Scientists have developed a new protein-based vaccine candidate for COVID-19 that they say is much easier to produce and does not need refrigeration.

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The research team at Boston Children's Hospital, US, noted that currently, available COVID vaccines require cold storage and sophisticated manufacturing capacity, which makes it difficult to produce and distribute them widely, especially in less developed countries.

They said the new vaccine design, described in the PNAS journal, could help fill global vaccination gaps and could be applied to vaccines against other diseases. The new vaccine candidate elicited strong immune responses against SARS-CoV-2, the virus that causes COVID-19, and its variants, the researchers said.

The vaccine was successfully freeze-dried and later reconstituted without losing efficacy, they said, adding it remained stable and potent for at least seven days at room temperature. The new experimental COVID-19 vaccine is completely protein-based, making it easy for many facilities to manufacture, according to the researchers.

It has two components: antibodies derived from alpacas, known as nanobodies, and the portion of the virus's spike protein that it uses to enter the human cells, they said. "We could also attach the whole spike protein or other parts of the virus," said study first author Novalia Pishesha.

"And we can change the vaccine for SARS-CoV-2 variants quickly and easily", Pishesha said. In experiments, the vaccine-elicited robust humoral immunity against SARS-CoV-2, stimulating high amounts of neutralising antibodies against the spike protein fragment.

It also elicited strong cellular immunity, stimulating the T helper cells that rally other immune defences, the researchers said. Because the vaccine is a protein, rather than a messenger RNA like the Pfizer/BioNTech and Moderna vaccines, it lends itself much more to large-scale manufacturing, they said.

"We don't need a lot of the fancy technology and expertise that you need to make an mRNA vaccine," said Thibault Harmand, co-first author of the study. "Skilled workers are currently a bottleneck for production of the COVID vaccine, whereas biopharma has a lot of experience producing protein-based therapeutics at scale," Harmand explained.

The new technology could potentially enable the production of the vaccine at many sites around the world, close to where it would be used, the researchers said. They have filed a patent on their technology, and hope to engage biotech or pharmaceutical companies to take their work into further testing and, eventually, a clinical trial.