What are examples of mRNA (messenger ribonucleic acid) vaccines?

mRNA Vaccines: Current Examples and Characteristics

The mRNA vaccines currently available are Pfizer-BioNTech (Comirnaty) and Moderna (Spikevax) COVID-19 vaccines, which are both lipid nanoparticle-encapsulated, nucleoside-modified mRNA vaccines encoding the SARS-CoV-2 spike protein. 1

What Makes a Vaccine an mRNA Vaccine?

mRNA vaccines represent a revolutionary approach in vaccine technology with distinct characteristics:

• Composition: mRNA vaccines contain messenger RNA encapsulated in lipid nanoparticles (LNPs)
• Mechanism: They deliver genetic instructions to cells to produce a specific protein (antigen) that triggers an immune response
• No live virus: Unlike some traditional vaccines, mRNA vaccines do not contain any live virus components

Currently Available mRNA Vaccines

According to the Advisory Committee on Immunization Practices (ACIP) and CDC guidance, the following are confirmed mRNA vaccines:

1. Pfizer-BioNTech (Comirnaty)

   • Contains nucleoside-modified mRNA (modRNA) encoding the SARS-CoV-2 spike glycoprotein
   • Formulated as lipid nanoparticles (LNPs)
   • Initially administered as a 2-dose primary series, 21 days apart 1

2. Moderna (Spikevax)

   • Contains nucleoside-modified mRNA (modRNA) encoding the SARS-CoV-2 spike glycoprotein
   • Formulated as lipid nanoparticles (LNPs)
   • Initially administered as a 2-dose primary series, 28 days apart 1, 2

How mRNA Vaccines Differ from Other COVID-19 Vaccines

For context, the following COVID-19 vaccines use different technologies:

• Janssen (Johnson & Johnson): Adenovirus vector-based vaccine 1
• Novavax: Adjuvanted, protein subunit-based vaccine 1, 3

Technical Characteristics of mRNA Vaccines

mRNA vaccines have several distinguishing technical features:

• They contain messenger RNA encoding viral proteins (specifically the spike protein for COVID-19 vaccines)
• The mRNA is encapsulated in lipid nanoparticles to protect it from degradation
• For COVID-19 bivalent boosters, the vaccines contain equal amounts of spike mRNA from both ancestral and Omicron variant strains 1
• The mRNA is modified (nucleoside-modified) to improve stability and reduce inflammatory responses 2

Clinical Significance

mRNA vaccines have demonstrated high efficacy in clinical trials:

• Pfizer-BioNTech: 95% efficacy in preventing symptomatic COVID-19 4
• Moderna: 94.1% efficacy in preventing symptomatic COVID-19 4

Important Considerations

• mRNA vaccines require special storage conditions due to their molecular composition
• They do not integrate into the host cell's DNA
• They are rapidly degraded after protein production, leaving no permanent genetic material
• The technology allows for rapid development and modification to address new variants 5, 6

The development of mRNA vaccine technology represents a significant advancement in vaccinology, with potential applications beyond COVID-19 for other infectious diseases and even therapeutic applications for conditions like cancer and genetic disorders 5, 6.