Same target, different cargo
The virus and the mRNA vaccine both get into our cells, but they bring very different instructions. The virus brings its whole genome, while the vaccine brings the code for one harmless part: the spike protein.
The virus invades
SARS-CoV-2 uses its spike proteins to latch onto ACE2 receptors and enter a cell. Then it releases its full RNA genome inside.
The virus multiplies
The cell's ribosomes are hijacked to build complete new viruses. Each infected cell releases many copies that spread the infection, and that is what makes you sick.
The vaccine delivers a recipe
The vaccine is a lipid bubble carrying mRNA for the spike protein only. It contains no virus and cannot cause COVID.
Only spikes are made
Ribosomes read the mRNA and make spike proteins, which appear on the cell surface. The mRNA never enters the nucleus and is broken down within days, so no new viruses can form.
The immune system learns
Immune cells see the spike, make antibodies against it and keep memory cells. Killer T cells learn to recognize infected cells too.
Ready for the real virus
If the real virus arrives later, antibodies block its spikes and T cells destroy infected cells quickly. The infection is stopped early or stays mild.