BEIJING– SINOVAC Biotech Ltd. (NASDAQ: SVA) (“Sinovac” or the “Company”), a leading provider of biopharmaceutical products in China, announced a paper, titled “A third dose of inactivated vaccine augments the potency, breadth, and duration of anamnestic responses against SARS-CoV-2,” is available on medRxiv. The findings suggest a third dose of CoronaVac® can induce a better neutralization breadth to variants of concern (“VOCs”), including the Delta variant, a rapid immunological memory response, and a long-lasting humoral response. Having a third dose of inactivated COVID-19 vaccine is more effective for COVID-19 prevention.
This study includes an in-depth exploration of the immunogenic profiles of antibodies from three and two-dose CoronaVac® recipients and convalescents. The findings indicate that three-dose vaccinees demonstrated better neutralization breadth to VOCs, expeditious recall, and long-lasting humoral immune response. Analysis of 171 complex structures of neutralizing antibodies identified structure-activity correlation and revealed ultrapotent, VOCs-resistant, and broad-spectrum patches.
As part of this study, researchers also constructed immunogenic and mutational heat maps, which revealed a direct relationship between “hot” immunogenic sites and areas with high mutation frequencies. Prolonged and repeated antigen stimulation can induce ongoing antibody somatic mutation, memory B cell clonal turnover, and antigen composition changes in B cell repertoire, which result in the development of monoclonal antibodies with enhanced neutralizing potency and breadth.
The above research provides a theoretical basis for a third dose of inactivated COVID-19 vaccine.