Nanoparticle Image
A schematic visualization of the ferritin nanoparticle with shortened coronavirus spike proteins, which is the basis of a SARS-CoV-2 vaccine candidate from Stanford. (Credit: Duo Xu)

A single-shot vaccine that does not require a cold-chain for storage or transport contains nanoparticles studded with the same proteins that comprise the COVID-19 virus’s distinctive surface spikes.

Initial tests in mice suggest that the Stanford nanoparticle vaccine could produce COVID-19 immunity after just one dose. The researchers are also hopeful that it could be stored at room temperature and are investigating whether it could be shipped and stored in a freeze-dried, powder form. By comparison, the vaccines that are farthest along in development in the United States all need to be stored at cold temperatures, ranging from approximately 8–70 °C (46–94 °F).

After a single dose, the two nanoparticle vaccine candidates both resulted in neutralizing antibody levels at least twice as high as those seen in people who have had COVID-19, and the shortened spike nanoparticle vaccine produced a significantly higher neutralizing response than the binding spike or the full spike (non-nanoparticle) vaccines. After a second dose, mice that had received the shortened spike nanoparticle vaccine had the highest levels of neutralizing antibodies.