##1. Structural Limitations of Linear mRNA and the Emergence of Next-Generation Platforms Current linear mRNA vaccines possess a 5' cap and a 3' poly‑A tail, rendering them highly susceptible to degradation by intracellular exonucleases. Consequently, protein expression is short‑lived, necessitating frequent booster administrations and imposing stringent cold‑chain logistics. To overcome these limitations, circular RNA (circRNA), which lacks free termini and adopts a closed‑loop configuration, has emerged rapidly as a next‑generation gene‑delivery platform.

##2. The Magic of the Ring Structure: Nuclease Resistance and Extended Protein Expression Because circRNA lacks free ends, it is resistant to the primary nucleases that degrade linear mRNA. Recent molecular analyses demonstrate that, in animal models, circRNA exhibits a markedly longer half‑life than linear mRNA and sustains protein production for several days. Theoretically, this permits sufficient antigen exposure with a lower RNA dose, providing a technical foundation for dramatically improving vaccine manufacturing efficiency and logistical convenience.

##3. Discrepancy Between Stability and Immunogenic Efficacy: An Unresolved Clinical Challenge However, studies have uncovered an "efficacy paradox" whereby the physical stability of circRNA does not necessarily translate into a robust immune response. Despite prolonged antigen production, neutralizing antibody titers and T‑cell response magnitudes are reported to be comparable to—or even lower than—those elicited by conventional linear mRNA. This suggests that the innate immune sensors (e.g., TLRs, RIG‑I) recognize circRNA differently and that translation efficiency requires further optimization.

##4. Why it Matters: Cold‑Chain‑Free Vaccines and a Shift in Immunization Paradigms The study is pivotal because it suggests a shift in vaccine performance metrics from short‑term, high‑dose antigen production toward sustained, long‑term immune homeostasis. If the high thermal stability of circRNA can be linked to genuine protective efficacy, it could eliminate the most formidable barrier to global vaccine distribution—the cold‑chain infrastructure. Moreover, a single administration that confers months‑long protection would inaugurate a "long‑acting" vaccine era, substantially reducing the economic burden of pandemic response and maximizing vaccination convenience.