How COVID-19 Vaccines Protect You

Updated June 30, 2022

COVID-19 vaccines protect you from getting sick

Local, regional, and national health experts recommend taking a vaccine against COVID-19. Right now, there are 3 vaccines authorized in the U.S.: Pfizer, Moderna and Johnson & Johnson. 

After looking more closely at the vaccines, national experts have decided that mRNA vaccines are preferred over Johnson & Johnson. People can still get the single dose J&J if they are unable to take a different kind of vaccine. Talk to your doctor if you have specific questions. 

Getting fully vaccinated and boosted is our best defense against COVID-19.

Medical experts are still learning how long the vaccines protect you and if they stop you from spreading COVID-19. It will take some time before enough people have the vaccine that we can stop using everyday prevention. 

What they do 

Both types of COVID-19 vaccines teach your body to recognize and fight the coronavirus. 

• The Pfizer and Moderna vaccines contain messenger RNA (mRNA). mRNA is like an instruction manual. It teaches your body how to make a harmless protein that looks like a protein on this coronavirus. Your body responds to the protein and creates disease-fighting cells and antibodies that can recognize and fight this coronavirus.
• The Johnson & Johnson vaccine is a viral vector vaccine. It contains a harmless adenovirus, from a family of viruses that causes the common cold. The adenovirus in the vaccine carries a gene from the spike protein of the coronavirus. This teaches your body how to recognize and fight the coronavirus that causes COVID-19.
• No matter what type of vaccine you get, your body will be ready to protect you if it sees this coronavirus in the future.

What they don’t do 

• They do not contain coronavirus and can’t give you COVID-19.
• They do not change your DNA or genetic material. 
• They do not cause infertility.

What’s in the COVID-19 vaccines? 

• The Pfizer and Moderna vaccines have mRNA and ingredients to help mRNA work in your body: fats, potassium, organic compounds to protect mRNA from too much acid, salt, and sugar. 

• The Johnson & Johnson vaccines have a modified adenovirus with information from the coronavirus on it. They also contain ingredients that help keep the vaccines stable: salts, sugars and other organic compounds.

• The vaccines do not contain eggs, preservatives, latex, pork or other animal products, or fetal cells.

Who can get these vaccines?

• Anyone 6 months - 17 must get Pfizer or Moderna.
• Adults 18 years and older can get any of the authorized vaccines. mRNA vaccines (Pfizer and Moderna) are preferred to the Johnson & Johnson vaccine. 

Talk with your doctor or clinic if you have any serious allergies.

Side effects

Many people experience mild side effects after getting the vaccine. This is a sign that your body is doing what it is supposed to do: building protection against the disease. 

• Common side effects include soreness or redness where you got the vaccine, a headache, tiredness, and/or low fever (less than 100.4). These symptoms are more common after the second dose. 
• These symptoms usually go away on their own within a few days. If they don’t, call your doctor or clinic. 

Rare, but serious, problems

Allergic reactions

It is rare, but some people have had a severe allergic reaction to the vaccine. All of these people received medical help right away. 

• Everyone who gets these vaccines must wait for at least 15 minutes afterwards, so medical staff can help them if they have a reaction. 
• If you’ve had a severe allergic reaction in the past, talk with your doctor or clinic.

Blood Clots

The Johnson & Johnson vaccine is linked to a rare, but serious, blood clotting problem. While people of any age or gender could experience blood clots following J&J, women ages 18-49 should be sure to understand the increased risk.
 
If you get the Johnson & Johnson vaccine, monitor yourself for these symptoms for three weeks after your shot:

• a severe headache or a headache that won’t go away 
• blurred vision 
• chest or severe belly pain 
• leg swelling or pain 
• trouble breathing 
• easy bruising or tiny blood spots under your skin outside of where you got your shot

 
If you have any of these symptoms, call 911 or seek medical attention.  It is important to tell the medical provider that you got the Johnson & Johnson vaccine so they can take care of you in the right way.

Symptoms of blood clots generally show up 1-2 weeks after vaccination. Anyone whose last J&J was at least 3 weeks ago no longer needs to watch for symptoms of a blood clot. 

Guillain-Barré Syndrome

Guillain-Barré syndrome (GBS) is a medical condition that affects the nervous system. Some people have gotten GBS in the 6 weeks after the J&J vaccine, but it is very rare.  

You should seek medical attention right away if you get any of the following symptoms after receiving the J&J vaccine: 

• • Weakness or tingling sensations, especially in the legs or arms
• • Difficulty walking 
• • Difficulty with facial movements, including speaking, chewing, or swallowing 
• • Double vision or inability to move eyes 
• • Difficulty with bladder control or bowel function  

Myocarditis or Pericarditis

Rarely, myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining outside the heart) have occurred in some people (mostly men aged 16 - 30 yrs) who have taken the Pfizer-BioNTech or Moderna COVID-19 vaccine. 

In most of these people, symptoms began a few days after the second dose of the vaccine. The chance of having this occur is very low — less than 1 in 10,000 people. Most cases are mild and get better on their own.

Seek medical attention right away if you have any of the following symptoms after receiving the vaccine:

• Chest pain 
• Shortness of breath 
• Feelings of having a fast-beating, fluttering, or pounding heart.

If you have any of these symptoms, call 911 or seek medical attention. It is important to tell the medical provider that you got the Johnson & Johnson vaccine so they can take care of you in the right way.