The Feasibility of Developing a Universal SARS-CoV-2 Vaccine.

As SARS-CoV-2 continues to evolve with increased transmissibility and immune evasion, the need for vaccines that provide broader and more durable protection has become increasingly urgent. The extensive research spurred by the pandemic has accelerated the development of diverse vaccine platforms, including mRNA, DNA, virus-like particles (VLPs), recombinant proteins, and mosaic mono- and polyvalent vaccines. While several of these platforms have reached regulatory approval and widespread clinical employment, others remain under evaluation or in various stages of clinical development. These vaccines have significantly reduced infection rates, severe disease, and hospitalizations, particularly among high-risk group. Nevertheless, the ongoing emergence of novel variants and subvariants has challenged the efficacy of both existing and newly developed vaccines. This evolving landscape underscores the urgent need for a universal SARS-CoV-2 vaccine platform capable of providing comprehensive and long-lasting immunity. In this review, we evaluate current and emerging strategies for SARS-CoV-2 universal vaccine development, with a focus on antigen design, breadth of immune protection, and clinical feasibility. Attention is given to various universal vaccine platforms such as the mosaic polyvalent spike construct, multi-epitope vaccines targeting the receptor-binding domain (RBD), and approaches centered on the conserved S2 subunit of the spike protein. We also discuss strategies leveraging additional conserved viral proteins and T helper (Th) and cytotoxic T lymphocyte (CTL) epitopes from across coronaviruses. By highlighting the advances in these areas, this review provides a framework to guide the rational design of next-generation universal vaccines capable of delivering broad and durable protection against SARS-CoV-2 variants.