Abstract: Compositions are disclosed that include alum and a SARS-CoV-2 Spike (S) glycoprotein variant covalently bound to the alum via at least one linker having 2-12 phosphoserine residues, where the S glycoprotein variant includes a receptor binding domain (RBD) having a mutation of at least one amino acid residue in an angiotensin-converting enzyme 2 (ACE2) receptor binding motif (RBM) relative to a wild-type RBD, where the residue is (i) hydrophobic; and (ii) within an aggregation-prone region of about 3-15 amino acid residues, and the mutation is a substitution of the hydrophobic residue with a different amino acid residue; as are compositions and vaccines including the compositions, and methods for their use.