| Summary: | Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a worldwide viral pandemic leading to global efforts to produce and distribute effective vaccines that prevent coronavirus virus disease 2019 (COVID-19) (1). The Spike protein and, more specifically, its receptor-binding domain (RBD) on the virus surface are responsible for binding to human angiotensin-converting enzyme 2 (hACE2) on the host cell. Hence, because of their central role in viral entry, the Spike and the RBD are established immunogens in SARS-CoV-2 vaccines (2, 3). mRNA-based and viral-vectored vaccines encoding the Spike protein have gained regulatory approvals and are being massively deployed presently. Despite their excellent protective efficacy against SARS-CoV-2, mRNA vaccines have well-known limited thermostability, and thus, global distribution is complicated by the requirement of ultracold freezing storage temperatures (4). As COVID-19 vaccines are needed worldwide to immunize sufficient populations to induce global herd immunity, including in low- and middle-income countries, there is more demand for vaccine doses than at any other time in history (5). A potent vaccine that is effective with a lower amount of antigen per dose would increase manufacturing and distribution capacity, facilitating the supply of global needs during the pandemic.
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