The first COVID-19 vaccines to hit the market in the U.S., from Pfizer and Moderna, use mRNA — a molecule that can teach your body how to fight a disease.
But how do the vaccines work?
When you encounter a virus like the common cold, it hijacks your cells and replicates itself. The virus spreads.
You have an army to protect you: your immune system. T-cells, B-cells and antibodies (which are shaped like a capital "Y") learn how the virus works so you can fight it off.
After they fight a virus, they usually remember the enemy. But your body has never encountered COVID-19.
That is why you need a vaccine, which will give your cells instructions on how to fight the intruder.
Common vaccines, like the flu vaccine, are made by growing live viruses in chicken eggs. With a worldwide pandemic, this method would take too long.
So scientists made a different type of vaccine in a test tube with a single-stranded molecule called messenger RNA.
Our cells naturally make mRNA. The cells copy a part of our DNA onto the mRNA. Then the cell uses mRNA as instructions to create proteins for things like digesting food.
Scientists discovered they could send in new mRNA with instructions to create a protein that looks like part of the coronavirus. It's like a blueprint, telling your cells what to do.
mRNA has not been used for mass vaccinations before. But scientists have been developing mRNA vaccines for Zika, the flu and cancer for years. So, they were able to quickly adapt it to attack the coronavirus.
It aced the same rigorous safety checks all other vaccines go through and was approved in record time thanks to the intense focus of the science community.
Now, imagine it's your turn to get vaccinated.
You get a shot and the mRNA in that syringe makes its way into your cells.
Your cells follow the mRNA instructions and create a special protein, called a spike protein. This spike protein is not the coronavirus, it just looks like part of one.
The mRNA cannot enter the cells' nuclei, where your DNA is stored. It cannot change your DNA.
Within a few minutes, the mRNA dissolves and the cell places the spike protein on the outside of its membrane.
And sure enough, your antibodies start attacking the spike proteins.
After the shot, you might feel rundown. You could develop a slight fever — which is a sign your body is learning to fight.
Your antibodies wait for a COVID-19 attack, but as the weeks go on, they sort of forget the lessons they learned.
Three to four weeks later, you go back for your second dose of the vaccination.
But this time, more cells join the fight.
Now, all the fighters in your immune system know how to handle a novel coronavirus infection.
These two vaccines are about 95% effective. We don’t know if you can still carry the disease, so you’ll still need to wear a mask and social distance to protect others.
Infectious disease physician, Rutgers New Jersey Medical School
Rutgers vice chancellor for translational medicine and science
Stat News, published November 10, 2020
What to Expect at Your Appointment to Get Vaccinated for COVID-19
Centers for Disease Control, updated January 22, 2021
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Published February 22, 2021