ACE2 and infection: The main target of many of the vaccines that have been designed is the spike (S) protein of SARS-CoV-2, which plays a central role in infection by interacting with angiotensin-converting enzyme 2 (ACE2) as a receptor for entry into host cells [3,4]; thus, most SARS-CoV-2 vaccines—whether they are genetic or protein vaccines—use part or all of the S protein [5].