PROS1 and COVID-19: The SpFN COVID-19 vaccine, developed by the US Army Medical Research and Development Command (USA), which is undergoing phase 1 clinical trials (NCT04784767), is represented by Helicobacter pylori ferritin nanoparticles containing the S protein ectodomain region (amino acid residues 12–1158), modified by the introduction of two proline residues (K986P and V987P) and the furin-cleavage site replacement (682-RRAR-685 -> GSAS).