mRNA Vaccines to Protect Against Diseases.

Infectious diseases are a leading cause of death worldwide, and vaccines are the cheapest and efficient approach to preventing diseases. Use of conventional vaccination strategies such as live, attenuated, and subunit has limitations as it does not fully provide protection against many infectious diseases. Hence, there was a need for the development of a new vaccination strategy. Use of nucleic acids-DNA and RNA-has emerged as promising alternative to conventional vaccine approaches. Knowledge of mRNA biology, chemistry, and delivery systems in recent years have enabled mRNA to become a promising vaccine candidate. One of the advantages of a mRNA vaccine is that clinical batches can be generated after the availability of a sequence encoding the immunogen. The process is cell-free and scalable. mRNA is a noninfectious, nonintegrating molecule and there is no potential risk of infection or mutagenesis. mRNA is degraded by normal cellular processes, and its in vivo half-life can be regulated by different modifications and delivery methods. The efficacy can be increased by modifications of the nucleosides that can make mRNA more stable and highly translatable. Efficient in vivo delivery can be achieved by formulating mRNA into carrier molecules, allowing rapid uptake and expression in the cytoplasm. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in late 2019 and spread globally, prompting an international effort to accelerate development of a vaccine. The spike (S) glycoprotein mediates host cell attachment and is required for viral entry; it is the primary vaccine target for many candidate SARS-CoV-2 vaccines. Development of a lipid nanoparticle encapsulated mRNA vaccine that encodes the SARS-CoV-2 S glycoprotein stabilized in its prefusion conformation conferred 95% protection against Covid-19.