A single-dose mRNA vaccine provides a long-term protection for hACE2 transgenic mice from SARS-CoV-2

The rapid expansion of the COVID-19 pandemic has made the development of a SARS-CoV-2 vaccine a global health and economic priority. Taking advantage of versatility and rapid development, three SARS-CoV-2 mRNA vaccine candidates have entered clinical trials with a two-dose immunization regimen. However, the waning antibody response in convalescent patients after SARS-CoV-2 infection and the emergence of human re-infection have raised widespread concerns about a possible short duration of SARS-CoV-2 vaccine protection. Here, we developed a nucleoside-modified mRNA vaccine in lipid-encapsulated form that encoded the SARS-CoV-2 RBD, termed as mRNA-RBD. A single immunization of mRNA-RBD elicited both robust neutralizing antibody and cellular responses, and conferred a near-complete protection against wild SARS-CoV-2 infection in the lungs of hACE2 transgenic mice. Noticeably, the high levels of neutralizing antibodies in BALB/c mice induced by mRNA-RBD vaccination were maintained for at least 6.5 months and conferred a long-term notable protection for hACE2 transgenic mice against SARS-CoV-2 infection in a sera transfer study. These data demonstrated that a single dose of mRNA-RBD provided long-term protection against SARS-CoV-2 challenge. Several mRNA-based vaccines for SARS-CoV-2 are in late phase clinical development. Here, the authors show that a single immunization with a mRNA vaccine expressing SARS-CoV-2 spike RBD induces neutralizing antibodies that are maintained for at least 6.5 months and confer protection in a sera transfer study in mice.

Automated summary

A nucleoside-modified mRNA vaccine encoding SARS-CoV-2 RBD, termed mRNA-RBD, provides long-term protection with a single immunization, inducing robust immune responses. Animal studies demonstrate that neutralizing antibodies induced by mRNA vaccine can be maintained for at least 6.5 months, providing protection in transfer studies.