u/Front_To_My_Back_

I wish I had a stool and I am as tall and lanky as Gianmarco Soresi to explain but anyway. Technically speaking, vaccines are peptides because they are proteins to begin with. Proteins in the most general sense are a collection of peptides, each peptides are composed of amino acids linked by a peptide bond between a carboxyl group and an amino group.

Since so many people nowadays are ordering peptides online without any regard for safety and efficacy, maybe it's time for the drug companies to get with the times and call vaccines as peptides?

• Recombinant Hep B: HBsAg is a protein in the surface of HBV
• RSV: recombinant F-protein subunit locked in the prefusion state using 2P mutation
• Flu: while most of the available vaccines are virion split, the dead virus contains the HA protein. Nowadays there's now recombinant HA vaccine I think
• Tetanus: it's definitely a protein, a toxoid to be precise
• Covid: While mRNA, mRNA once inside cells produce peptides of the spike
• Measles: while a live attenuated virus, its surface does contain proteins that are immunogenic

And many more vaccines...just my two cents