---
title: 'How mRNA Vaccines Work (Covid-19 Pfizer and Moderna)'
source: 'https://youtube.com/watch?v=fZLxvo21XDg'
video_id: 'fZLxvo21XDg'
date: 2026-06-13
duration_sec: 157
---

# How mRNA Vaccines Work (Covid-19 Pfizer and Moderna)

> Source: [How mRNA Vaccines Work (Covid-19 Pfizer and Moderna)](https://youtube.com/watch?v=fZLxvo21XDg)

## Summary

This video explains how mRNA vaccines, such as those developed by Pfizer/BioNTech and Moderna against COVID-19, work. It describes the central dogma of molecular biology (DNA to RNA to protein) and how the vaccine uses messenger RNA to instruct cells to produce the spike protein of SARS-CoV-2, triggering an immune response.

### Key Points

- **Central Dogma** [00:00] — Genetic information flows from DNA to RNA to proteins. mRNA vaccines focus on the RNA-to-protein step.
- **Spike Protein Target** [00:30] — SARS-CoV-2 has 29 proteins; the spike protein on its outer membrane is crucial for cell infection.
- **mRNA Isolation** [00:45] — Companies isolated the mRNA that encodes the spike protein from the virus's genetic makeup.
- **mRNA Structure** [01:15] — The mRNA has 5' and 3' UTRs, a coding region, and start/stop signals for ribosomes.
- **Lipid Nanoparticle Delivery** [01:30] — mRNA is packaged in a lipid nanoparticle to fuse with human cells and deliver the mRNA inside.
- **Protein Production** [01:45] — Ribosomes use the mRNA to produce spike protein using amino acids from the body.
- **Immune Response** [02:15] — Cells recognize the spike protein as foreign, triggering macrophages to destroy the cell and present the antigen to B and T cells.
- **Antibody Production** [02:45] — B cells produce antibodies against the spike protein; T cells remember the antigen for future infections.
- **Protection Mechanism** [03:00] — If infected later, antibodies bind to the spike protein on the virus, marking it for destruction by macrophages before it can infect cells.

### Conclusion

mRNA vaccines safely teach the immune system to recognize and neutralize the spike protein of SARS-CoV-2, providing protection without causing disease.

## Transcript

Our genetic information can be carried in 
three main ways. This first begins with DNA   that encodes the blueprints to make RNA that has 
the instructions to make proteins, which are then   going to function in every cell in our body. Now 
the Pfizer/BioNTec or Moderna vaccines against   coronavirus focus on the second branch of this 
pathway mRNA or messenger RNA. Now this has been   used in the past for gene therapy or for cancer 
treatment but is now being used for SARS-CoV-2.   And the coronavirus has 29 main proteins but 
the specific protein that's found on the outer   membrane is known as the spike protein, which is 
really important for it to infect a healthy cell.   Now what these companies did is they looked at 
the entire genetic makeup of SARS-CoV-2 and found   the single mRNA that encodes for the instructions 
to make the spike protein. They isolated out this   mRNA that can now be injected into us in the form 
of a vaccine to make one of these 29 proteins,   thus not giving us an actual coronavirus. Now this 
mRNA is important as it's been structured to have   a three prime and a five prime UTR, a coding 
region, and a place for the ribosome to start   and stop. It's then been packaged into a lipid 
nanoparticle which is critical for it to fuse   with our human cells thus allowing the vaccine or 
mRNA to now enter into our cells. This recruits   the ribosomes and initiation factors since this 
RNA looks just like endogenous RNA that we would   make ourselves. It will then use amino acids 
that we've consumed to build the spike protein.   Now that's when our cells begin to say wait 
a second we haven't seen this protein before.   So they elicit an immune response to bring in 
a macrophage to come and destroy this cell that   just got the vaccine. But, before the macrophage 
destroys this cell it's going to remember that   this spike protein was different. It was a foreign 
antigen that it's going to send the information to   our lymphatic system which is composed of B cells 
that are now going to make antibodies against this   antigen, and T cells which are now going to be 
on the lookout for this antigen in the future. So   if we are newly infected with SARS-CoV-2 
the antibodies that we've now produced are   going to bind with the antigen present on 
the outside of SARS-CoV-2 and direct the   coronavirus for destruction by macrophages 
before the coronavirus can infect our cells