mRNA vaccine

mRNA vaccines work by introducing a synthetic mRNA sequence encoding a target antigen into host cells. The mRNA is delivered via lipid nanoparticles (LNPs) that facilitate cellular uptake. Once inside the cytoplasm, the mRNA is translated by ribosomes into the antigen protein, which is then processed and presented on the cell surface, triggering both humoral and cellular immune responses.¹ The mRNA itself is inherently unstable and does not integrate into the host genome, as it is degraded after translation.²

The concept of mRNA vaccines dates back to the early 1990s, when in vitro transcribed mRNA was shown to be expressed in mice.³ However, initial challenges included mRNA instability and innate immune activation. Key advances in nucleoside modification, such as the use of pseudouridine, were pioneered by Katalin Karikó and Drew Weissman, reducing immunogenicity and increasing translation efficiency.⁴ The first mRNA vaccines were authorized for emergency use against COVID-19 in December 2020, developed by Pfizer–BioNTech and Moderna, achieving over 90% efficacy in clinical trials.⁵

mRNA vaccines offer several advantages: rapid production, as they can be synthesized in weeks once the antigen sequence is known; flexibility to target multiple antigens; and a non-infectious platform that does not require cell culture. They have been used successfully against COVID-19, and are being investigated for other infectious diseases such as influenza, Zika, and rabies, as well as for cancer immunotherapy. The platform also allows for rapid adaptation to new variants, as seen with updated COVID-19 boosters.

Despite their promise, mRNA vaccines face challenges including cold-chain storage requirements, potential for rare adverse effects like myocarditis, and the need for lipid nanoparticle delivery systems. Early mRNA vaccines required storage at −70°C, though formulations have improved to allow refrigerator storage. Additionally, the technology is relatively new, and long-term durability of immune responses is still being studied.⁶

Beyond COVID-19, mRNA vaccines are being explored for personalized cancer vaccines, where mRNA encoding tumor-specific neoantigens is tailored to an individual's tumor mutations. Another niche application is in allergy immunotherapy, where mRNA encoding allergens could induce tolerance. The technology also has potential for therapeutic protein replacement, such as producing enzymes in vivo. Notably, the 2023 Nobel Prize in Physiology or Medicine was awarded to Katalin Karikó and Drew Weissman for their nucleoside base modifications that enabled the development of effective mRNA vaccines.⁷

Lipid nanoparticle (LNP)

A delivery vehicle composed of lipids that encapsulates mRNA to protect it and facilitate cellular uptake.

Pseudouridine

A modified nucleoside that reduces innate immune activation and increases mRNA translation.

Neoantigen

A tumor-specific antigen derived from mutations, used in personalized cancer vaccines.