Viral vaccine vector for immunization against a betacoronavirus

An immunogenic construct of a betacoronavirus, comprising

• (i) the spike receptor binding domain (RBD) of a betacoronavirus, wherein the RBD preferably comprises SEQ ID NO:
• 1 or a variant of SEQ ID NO:
• 1 being with increasing preference at least 80%, at least 85%, at least 90% and at least 95% identical to SEQ ID NO:
• 1, and C-terminally thereof;
• (ii) a transmembrane anchor being derived from the stem of a rhabodovirus glycoprotein, and preferably derived from members of the Lyssavirus genus, more preferably derived from the rabies (RABV) vaccine strain SAD B19 (molecular clone SAD L16), and most preferably comprising or consisting of the membrane proximal part of the G ectodomain, the trans-membrane and the cytoplasmic tail of the RABV SAD L16 G protein;
• and
• (iii) at the N-terminus a signal peptide that promotes high-level translation into the endoplasmatic reticulum.