Understanding How Covid Vaccines Work

George J. Ziogas

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Your immune system fights germs, known as pathogens, to help keep you from getting contagious diseases. Covid vaccines help give you immunity without contracting the disease and possibly spreading it to other people. The Covid vaccines use different technology, known as mRNA and viral vector technology, then most vaccines created in the past.

Your Immune System

The Covid vaccines allow your body to build antibodies against the Covid pathogen without first getting sick from the disease. Suppose you've had the disease and recovered. In that case, your body remembers the pathogen, so the next time you are exposed, your immune system immediately recognizes it and begins to fight against it.

Most previous vaccines use a weakened or inactivated virus to create immunity. Your immune system is exposed, but the pathogen used won't give you the disease. Covid vaccines don't use the actual virus to develop immunity. Instead, they use mRNA and viral vector technology, so you're not exposed to the pathogen itself.

mRNA Vaccines

Scientists began studying mRNA over 30 years ago. The previous process of creating a vaccine was time-consuming and required testing at each stage of development. The goal of mRNA vaccines was to develop a framework that could be used repeatedly for different pathogens and shorten the time it takes to create a vaccine. mRNA vaccines use a modified RNA molecule to deliver instructions to your immune system to build immunity.

RNA is a messenger in your body that can move from cell to cell. According to a study in the journal Nature, mRNA can be coded to instruct your immune cells against a specific pathogen.

The Covid pathogen is a virus that carries a protein on its surface. Your immune system can recognize the protein as being from the pathogen. mRNA Covid vaccines are coded to tell your cells to create the protein. By itself, the protein can't give you Covid, but your immune system thinks you've been exposed and begins to build immunity. The Pfizer and Moderna Covid vaccines are mRNA vaccines.

Viral Vector Vaccines

Like mRNA vaccines, a viral vector doesn't use the pathogen itself to create the vaccine. Instead, a different, non-harmful virus is used to expose you to the Covid virus protein. The non-harmful virus is known as a vector.

Once your body recognizes the Covid protein, it begins to build immunity to the pathogen. The Johnson and Johnson Covid vaccine is a viral vector vaccine.


The Covid mRNA vaccines require two doses. The viral vector Covid vaccine requires one. According to information published in the journal Young Scientists, it is not uncommon for a vaccine to need two doses for complete immunity. The first dose teaches your cells to recognize the pathogen, while the second dose boosts the immune response.

According to researchers at Ochsner Health, a single-dose vaccine does not mean it is less effective than a two-dose vaccine. The number of doses is determined during clinical trials. In the Pfizer Covid vaccine clinical trial, one dose was 52% effective at preventing disease, while a second dose raised the effectiveness to 95%.

Storage and Handling

According to the Centers for Disease Control (CDC), none of the Covid vaccines contain preservatives. Because of this, the Covid vaccines need to be shipped and stored under controlled temperatures and are not effective if they have been at room temperature for more than a few hours.

The amount of time is different among vaccines, so staff giving the vaccines must monitor each vaccine type's storage temperature and discard it when the allotted time has expired.

Emergency Use Authorization

All current Covid vaccines are being used under an Emergency Use Authorization from the United States Food and Drug Administration (FDA). Each vaccine was tested in large-scale clinical trials for safety and effectiveness for the Emergency Use Authorization was granted. Scientists continue to study the Covid vaccines as more people are vaccinated to monitor safety and effectiveness.

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