According to available data, the receptor-binding domain (RBD) of the viral spike (S) protein confers a transmission advantage through two key mechanisms [2]: first, by improving its binding affinity to the host angiotensin-converting enzyme 2 (ACE2), which increases infectivity; and second, by promoting immune evasion, which weakens immunity gained from prior infection or immunization by decreasing the effectiveness of neutralizing antibodies (NAbs). Here, ACE2 is linked to infection.