How do COVID vaccines work?
COVID vaccines, like all vaccines, work by training your immune system to fight off harmful germs (pathogens) that attempt to invade your body. But what does that mean? First, we have to understand how your immune system fights off viruses, bacteria and other pathogens.
Adaptive immunity
Each pathogen has a unique part that your body recognizes as an invader, called an antigen. It’s like a distinctive birthmark or tattoo you look for to identify someone. In COVID-19, it’s a protein that sticks out all around the outside of the virus (the spike protein).
The first time an invader, like a virus or bacteria, enters your body, your immune system needs to look for the right tools (specific B-cells) to recognize the antigen and destroy the pathogen it belongs to. When your immune cells find the right tools, they make a lot of them to find and get rid of the infection. But this process can take some time.
You also have special cells that remember the pathogen (memory B-cells). Like taking a photo and putting it on a “wanted” poster, your immune cells can then patrol your body, looking for familiar pathogens. If they encounter one, they can destroy it much more quickly than the first time it infected you — often before it makes you sick at all. This is called adaptive immunity.
COVID vaccines aim to tell your body what SARS-CoV-2 looks like without actually getting an infection. Then your immune system can build up its tools and surveillance team, so when it sees the virus, it can fight it off quickly. For some people, this means they don’t get sick at all if they’re exposed to COVID. Other times, it makes their symptoms less severe and allows them to recover more quickly.
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What types of COVID vaccines are there?
There are currently three updated COVID-19 vaccines available in the U.S. They’re categorized based on the method they use to get your body to recognize the spike protein of SARS-CoV-2.
- mRNA vaccines (Moderna® and Pfizer-BioNTech®). These use the instructions for a part of the virus (mRNA) to train your immune system.
- Protein subunit vaccines (Novavax®). These use a part of the virus to train your immune system.
Viral vector vaccines (Johnson & Johnson/Janssen®) are no longer available in the U.S. These used a different, harmless virus and a small part of COVID’s genetic code (DNA) to train your immune system.
mRNA vaccines
mRNA vaccines don’t use a part of the virus to train your immune system. Instead, they give your body instructions that it uses to manufacture harmless proteins that look like parts of the virus (in the case of COVID, the spike protein). Moderna and Pfizer-BioNTech vaccines are mRNA vaccines. Your body uses the mRNA instructions to make the spike protein for your immune system to recognize.
Protein subunit vaccines
Protein subunit vaccines use a part of the virus to get an immune system response. The Novavax vaccine delivers the spike protein to your cells so they can recognize and be prepared to destroy it if they see it again. Since it’s just part of the virus and not the actual virus itself, it can’t make more copies of itself or hurt you.
How should I prepare for a COVID vaccine?
Before getting your COVID shot, you should:
- Make sure you have an appointment if you need one. Many places that give COVID vaccines in the U.S. require an appointment. You might also need to see if the cost of the shot is covered by your insurance (or federal programs that cover the cost) at that location.
- Bring your vaccination card with you. Make sure you get proof of vaccination if you need it for work, school or travel.
- Avoid taking ibuprofen (Advil®, Motrin®) or acetaminophen (Tylenol®) to prevent vaccine side effects (it’s okay to take them to treat side effects if they happen). It’s possible these medications could reduce your immune response to the vaccine. Talk to a healthcare provider before getting vaccinated if you regularly take these medications to treat another condition and are concerned about their effects on your immune response. You usually don’t have to stop taking them before getting vaccinated.
- Make sure you have enough time after your appointment to wait for 15 minutes before leaving.
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What happens when you get your COVID vaccine?
Healthcare providers give all COVID vaccines as injections (shots). In adults and children over 5, a provider gives you the injection into the muscle of your upper arm. In children under 5, the injection is in their thigh (though 3- and 4-year-olds sometimes get it in their arms).
A provider will clean the area with an alcohol swab and inject the vaccine with a needle. They’ll put a bandage over it. Sometimes they’ll put a small, round bandage (a pre-injection bandage, or an Inject-Safe™ barrier bandage) on first and inject the needle into your skin through the bandage.
Your provider may ask you to wait at least 15 minutes before leaving to make sure you don’t have an immediate allergic reaction.
How long does the COVID vaccine last?
Studies suggest COVID vaccines are most effective in the first few months following your shot. That’s why when health experts recommend boosters or updated doses, they’re usually given three to four months after your last COVID shot.
