An overview of protein-based SARS-CoV-2 vaccines

SARS-CoV-2 resulted in the COVID-19 pandemic which, to date, has resulted in an estimated loss of over 15 million human lives globally and continues to have negative social, and economic implications worldwide. Vaccine platforms that can be quickly updated to counter newly emerging SARS-CoV-2 variants are critical in combating the COVID-19 pandemic. Messenger RNA-based SARS-CoV-2 vaccines can be easily updated and have shown superior efficacy over other vaccine types, yet their high cost, reactogenicity, and stringent need for ultracold storage limit their accessibility. Global access to economic, safe, and effective SARS-CoV-2 vaccines is a critical step toward reducing COVID-19-associated mortality and ending the pandemic. Several protein-based SARS-CoV-2 vaccines targeting the spike protein (or its receptor-binding domain) have demonstrated safety and efficacy in clinical studies. Moreover, protein-based vaccines can be updated to immunize against new virus variants. Protein-based vaccines do not contain live viruses and are safe to use in immunocompromised and elderly populations, and can be optimized to improve the immune outcome in these poorly immunoresponsive individuals by using adjuvants. SARS-CoV-2 shows high genetic variability, similar to other RNA viruses, and protein-based vaccines are an economically feasible vaccine platform that can be used to design new vaccines with durable protective immunity, in addition to expanding the vaccine coverage.