COVID-19 mRNA vaccine
Comirnaty is BioNTech's mRNA vaccine for the prevention of coronavirus disease 2019 (COVID-19). As SARS-CoV-2 keeps evolving, Comirnaty has been adapted to target the most recent strains of the virus.
This page is based on the EMA medicine record, the EMA product information and the current FDA-approved label (DailyMed) for Comirnaty; the mechanism is explained in plain language, and analogies are used only where they stay accurate.
How it works
Explains what the medicine does in the body, not dosing, side effects, or safety.
An analogy
Rather than showing the immune system a weakened virus, this vaccine hands over an instruction sheet - a piece of mRNA describing one coronavirus protein. Local cells read the instructions and briefly display that protein, and the immune system trains against it. The vaccine does not contain the virus itself and cannot cause COVID-19; the trained defenders remain, ready to recognise the real virus on sight.
In simple terms
Comirnaty is an mRNA vaccine. It contains nucleoside-modified messenger RNA encoding the viral spike (S) protein of SARS-CoV-2, embedded in lipid nanoparticles. After injection, the nanoparticles enable delivery of the non-replicating RNA into host cells, which then produce the spike antigen. The vaccine elicits an immune response to this antigen, which protects against COVID-19. If the vaccinated person later encounters SARS-CoV-2, those responses help protect against the disease. Only the spike protein is made - the vaccine does not contain the virus itself and cannot cause COVID-19.
In depth
The nucleoside-modified messenger RNA in Comirnaty is formulated in lipid nanoparticles, which enable delivery of the non-replicating RNA into host cells to direct transient expression of the SARS-CoV-2 S antigen. The mRNA codes for membrane-anchored, full-length S with two point mutations within the central helix; mutation of these two amino acids to proline locks S in an antigenically preferred prefusion conformation. The vaccine elicits both neutralising antibody and cellular immune responses to the spike (S) antigen, which may contribute to protection against COVID-19. As SARS-CoV-2 keeps evolving, Comirnaty has been adapted to target the most recent strains of the virus: the EMA record now lists versions named Comirnaty JN.1, Comirnaty KP.2, Comirnaty LP.8.1 and Comirnaty XFG. The JN.1 version contains bretovameran and the KP.2 version contains cemivameran, each a single-stranded, 5’-capped messenger RNA produced using a cell-free in vitro transcription from the corresponding DNA templates, encoding the viral spike (S) protein of SARS-CoV-2 of the corresponding Omicron subvariant; the LP.8.1 and XFG versions are described in the same product information as the mRNA encoding LP.8.1 and the mRNA encoding XFG. The first version, authorised on 21/12/2020, encoded the viral spike (S) glycoprotein of the Wuhan-Hu-1 strain (Original) and carried the name tozinameran, a pairing still visible in EMA's own safety documents from that period. In the United States the current label names the product COMIRNATY (COVID-19 Vaccine, mRNA) and describes each 0.3 mL dose of the 2025-2026 Formula as containing 30 mcg of a nucleoside-modified messenger RNA (modRNA) encoding the viral spike (S) glycoprotein of SARS-CoV-2 Omicron variant sublineage LP.8.1.
See it in motion
A schematic animation of the mechanism — simplified for clarity, not drawn to scale.
How mRNA vaccines teach the immune system to recognise a pathogen
- The vaccine delivers mRNA wrapped in a lipid particle into muscle cells near the injection site.
- The cells read the mRNA and make an optimized, non-infectious version of the virus's full-length surface spike protein.
- Immune cells spot that protein, learn its shape and build antibodies and T cells against it.
- If the real pathogen arrives later, the immune system neutralises it before it can cause illness.
Target: SARS-CoV-2 spike glycoprotein
The spike (S) protein of SARS-CoV-2. The vaccine's mRNA carries the instructions for producing this antigen, so cells produce it and the vaccine elicits an immune response to it.
Approved uses
Approved uses differ by country and change over time. Always follow your local prescribing information.
Approved uses in European Union
EMA- Active immunisation to prevent coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 in individuals 6 months of age and older
Official sources
The statements on this page trace back to these records.
- EMA Comirnaty product information (SmPC and PIL)
European Medicines Agency
- DailyMed label: COMIRNATY (COVID-19 Vaccine, mRNA), SPL v21 (2025-2026 Formula, LP.8.1)
DailyMed, U.S. National Library of Medicine
- National Cancer Institute: tozinameran
National Cancer Institute
This page explains how the medicine works — it isn’t the patient leaflet. For anything that applies to you, read the leaflet that came with your medicine or ask your pharmacist.
MedUnfold provides educational content and is not medical advice. Always follow your local prescribing information and healthcare professional.