S-only Omicron vaccine candidate

The **S-only Omicron vaccine candidate** is an experimental mRNA-based vaccine developed by researchers at the **University of Hong Kong** (HKU) to target the **SARS-CoV-2 Omicron variant** (specifically the BA.1 subvariant). Utilizing a lipid nanoparticle (LNP) delivery system, the vaccine encodes the full-length spike (S) protein of the Omicron variant. It was primarily developed as a research tool to evaluate the protective efficacy of spike-only antigens against the highly mutated Omicron variant, which has shown significant escape from immunity induced by original (ancestral) strain vaccines. In preclinical studies, including those published in *Nature Communications*, the S-only candidate was compared against a dual-antigen "S+N" (Spike and Nucleocapsid) vaccine. The results indicated that while the S-only vaccine could elicit high titers of neutralizing antibodies, it provided limited protection against upper respiratory tract infection and viral shedding in animal models, suggesting that broader antigenic coverage or mucosal delivery might be required for more effective control of Omicron transmission.

Other names

Omicron-specific spike-only mRNA vaccineHKU-S-Omicron