Single-Dose COVID-19 Vaccine Works in Mice

Single-Dose COVID-19 Vaccine Works in Mice


The COVID-19 pandemic, caused by the coronavirus SARS-CoV-2, is an ongoing global disruption. Large amounts of effective vaccines are urgently needed to fight the pandemic. The vaccines authorized so far require two doses to be effective, which can create problems with logistics and compliance. Vaccines that are effective after only a single dose would, thus, be useful. The primary target for COVID-19 vaccines is the spike protein, which is necessary for the virus’ entry into cells. The currently authorized mRNA vaccines cause human cells to temporarily produce the spike protein, triggering an immune response and antibody production.

Peter S. Kim, Stanford University and Chan Zuckerberg Biohub, San Francisco, both CA, USA, and colleagues have developed a nanoparticle vaccine that causes a virus-neutralizing antibody response in mice after only a single dose. The vaccine consists of multiple copies of the spike protein displayed on ferritin nanoparticles. Ferritin is an iron-storage protein found in many organisms that self-assembles into nanoparticles. The researchers combined spike protein and ferritin DNA and then expressed the resulting hybrid protein in mammalian cell cultures. The ferritin self-assembled into nanoparticles, each bearing eight copies of the spike protein.

The team purified the spike/ferritin particles and injected them into mice. After a single immunization, mice produced neutralizing antibody titers that were at least two times higher than those in convalescent plasma from COVID-19 patients, and significantly higher than those in mice immunized with the spike protein alone. According to the researchers, using spike/ferritin nanoparticles may be a viable strategy for single-dose vaccination against COVID-19. However, the results must be confirmed in human clinical trials.

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