Some side effects are common after vaccination. They are a result of your body responding to the vaccine (it's also OK if you don't have any side effects at all). Side effects happen within a day or two of vaccination and go away one to two days later. You may have:
Pain where you received the vaccine
Achy muscles and joints
Swelling in your armpit
If your symptoms don't go away or get worse, you may have been exposed to COVID-19 before your body had time to build the protection from the vaccine. Get tested if you think you may have COVID-19.
Serious adverse events
A serious adverse event is something that results in hospitalization or is life-threatening. Most adverse effects occur in the six weeks after getting a vaccine.
If you have a severe reaction, contact your health care provider. If it is an emergency, go to a hospital or call 911.
There have been reports of some serious allergic reactions or anaphylaxis, most occurring 15-30 minutes following vaccination. Allergic reactions like this are known to happen after taking medicines or getting vaccinated, but they are still very rare. Clinics are prepared to respond quickly to adverse reactions. You will be asked to wait 15-30 minutes after you have been vaccinated so that clinic staff can observe you.
Myocarditis and pericarditis
Some people who have received the Pfizer or Moderna COVID-19 vaccines have had rare cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining outside the heart). In most cases, symptoms began within seven days after the second dose of COVID-19 vaccine. Most cases of myocarditis and pericarditis have been in young men. The chance of having this occur is very low and is higher in people with COVID-19 disease than after vaccination. Seek medical attention right away if you have any of the following symptoms after receiving COVID-19 vaccine:
Shortness of breath
Feelings of having a fast-beating, fluttering, or pounding heart
For more information, visit CDC: Myocarditis and Pericarditis Following mRNA COVID-19 Vaccination.
A few people who have received the Johnson & Johnson COVID-19 have experienced Guillain-Barré Syndrome (GBS). GBS is a rare disorder where the body's immune system damages nerve cells, causing muscle weakness and sometimes paralysis. Most people fully recover from GBS, but some have permanent nerve damage. The benefits of vaccination outweigh the slight risk of this side effect and the chance of having this occur is very rare.
Symptoms of GBS have mostly been reported about two weeks after someone gets vaccinated and mostly in men ages 50-64 years of age. CDC will continue to monitor for and evaluate reports of GBS happening after COVID-19 vaccination and will share more information as it becomes available.
Seek medical attention right away if you have any of the following symptoms after receiving the Johnson & Johnson vaccine:
Weakness or tingling sensations, especially in the legs or arms, that's worsening and spreading to other parts of the body
Hard time walking
Hard time with moving your face, including speaking, chewing, or swallowing
Double vision or not being able to move eyes
Difficulty with bladder control or bowel function
Blood clotting issues (thrombosis with thrombocytopenia syndrome, TTS)
Some people who have received the Johnson & Johnson COVID-19 vaccine have developed blood clots involving blood vessels in the brain, abdomen, and legs along with low levels of platelets (blood cells that help your body stop bleeding). Most people who developed these blood clots and low levels of platelets were adult women younger than 50 years old. The chance of having this occur is very rare. For women 50 years and older and men of all ages, this adverse event is even more rare. For three weeks after receiving the Johnson & Johnson COVID-19 vaccine, be on the lookout for these symptoms:
Shortness of breath
Abdominal/stomach pain that doesn't go away
Severe headaches or headaches that won't go away
Easy bruising or tiny blood spots under the skin beyond the site of the injection
If you have any of these symptoms after getting the vaccine, you should seek medical attention right away. Tell the health care provider that you recently received the Johnson & Johnson vaccine.
If you got the Johnson & Johnson vaccine more than a month ago, you are unlikely to develop this condition.
People with a history of TTS following a COVID-19 vaccine should not get the Johnson & Johnson COVID-19 vaccine. These people should receive a dose of an mRNA COVID-19 vaccine (Pfizer or Moderna) as a booster at least 2 months following their dose of the Johnson & Johnson COVID-19 vaccine and after their clinical condition has stabilized. Learn more at CDC: Interim Clinical Considerations for Use of COVID-19 Vaccines: Considerations for Janssen COVID-19 Vaccine.