1 INTRODUCTION
The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus (SARS‐CoV‐2), has persisted for more than three years1, and numerous variants have emerged globally. In early December 2022, China lifted its COVID-zero policy, followed shortly by the quick spread of the SARS-CoV-2 Omicron variant across most parts of the country.2 Although vaccination with wild-type SARS-CoV-2 vaccines did not appear to provide significant protection against Omicron in Beijing, most people only experienced influenza-like symptoms. By February 2023, only sporadic COVID cases were reported each day, indicating that herd immunity against Omicron variants was achieved in a relatively short period in China. However, concerns remain regarding the effectiveness of this immunity against future spillovers of SARS-CoV-2-like viruses.
To address this issue, we analyzed the neutralizing antibodies in sera from wild-type SARS-CoV-2 vaccine recipients who recovered from Omicron BF.7 variant infection by performing viral neutralizing assays with a SARS-CoV-2-related pangolin coronavirus GX_P2V3. The differences between SARS-CoV-2 and GX_P2V primarily lie in the spike glycoprotein (S), a primary target for neutralizing antibody (Figure S1). However, compared to SARS-CoV-2, the spike protein of pangolin-CoV GX_P2V has a comparable binding affinity to human ACE2 but has a distinct receptor binding domain (RBD)4 (Figure 1A), making it a practical model for testing neutralizing antibodies against unpredictable SARS-CoV-2 related viruses.