COVID-19: Vaccine safety and side effects

This type of vaccine helps your cells make a coronavirus protein. This protein will trigger an immune response that will help protect you against COVID-19. Once triggered, your body makes antibodies. These antibodies help you fight the infection if the real virus does enter your body in the future.

mRNA vaccines don't use a live virus to trigger an immune response. You can't get COVID-19 from the vaccine and it doesn't interact with your DNA or change it in any way.

Learn more about mRNA vaccines

This type of vaccine uses a harmless virus (in this case, an adenovirus) as a delivery system. This delivery system helps your cells to make a coronavirus protein.

The protein will trigger an immune response that will help protect you against COVID-19. The adenovirus isn't the virus that causes COVID-19. You can't get COVID-19 from the vaccine.

Learn more about viral vector vaccines

Protein subunit vaccines contain harmless and purified pieces (proteins) of the virus, which have been specifically selected for their ability to trigger immunity. Once vaccinated, your immune system triggers an immune response that will help protect you against COVID-19.

Protein subunit vaccines are already used to protect against other diseases, such as hepatitis B. They can't cause COVID-19 because they only contain small purified pieces of proteins and not the virus itself.

Learn more about protein subunit vaccines

This type of vaccine uses plant-based technology. The virus' genetic code is delivered to the leaf cells of the plant using harmless bacteria. The plant's natural cell process is used to produce a non-infectious virus-like particle that mimics the spike virus that causes COVID-19. Your body's immune system then responds to it in the same way it would if it encountered the real virus.

Through this process, your body can mount a strong immune response without exposing you to the virus that causes COVID-19.

Learn more about plant-based vaccines

You can take over-the-counter medicine after your vaccination to help with any pain or to lower a fever.

For pain where the needle was given, you can:

• apply a clean, cool, wet washcloth over the area that received the injection
• gently use or stretch your arm

Contact a health care provider if:

• you have questions about how to manage any symptoms
• you're concerned about any symptoms you're experiencing after vaccination

It's possible for most people who experienced an allergic reaction to a COVID-19 vaccine to safely receive future doses of that same vaccine. This includes with an mRNA vaccine.

The National Advisory Committee on Immunization has recommendations for people who experienced a severe immediate allergic reaction after a first dose of an mRNA COVID-19 vaccine. People with a history of a severe immediate allergic reaction after a first dose of an mRNA COVID-19 vaccine should:

• consult with an allergist or another appropriate health care provider before receiving future doses of an mRNA COVID-19 vaccine
• receive future doses of an mRNA COVID-19 vaccine in a controlled setting with someone who is experienced in managing anaphylaxis
• be observed for at least 30 minutes after vaccination
  • the normal observation period for people who haven't experienced a severe immediate allergic reaction after vaccination is 15 minutes

If you know you're allergic to a component of an mRNA COVID-19 vaccine, consult with an allergist or your health care provider. It may still be possible for you to receive these vaccines.

Rare reactions have been reported following vaccination with mRNA COVID-19 vaccines related to:

• myocarditis (inflammation of the heart muscle)
• pericarditis (inflammation of the lining around the outside of the heart)

Seek immediate medical attention if you experience any of the following symptoms after getting a vaccine:

• chest pain or pressure
• irregular heartbeat or rhythm, including too quick, too slow or an irregular pattern of heartbeat
• shortness of breath

Myocarditis and pericarditis seem to be occurring more often than expected in some populations and situations, such as:

• in adolescents and young adults
• in males
• following the second dose
• typically occurring within 7 days after vaccination

In the majority of cases, symptoms of myocarditis or pericarditis resolve quickly after seeking medical care.

Additional doses and booster doses

In most cases, someone who has had myocarditis or pericarditis after an mRNA vaccine should defer receiving another dose.

The rates of these conditions after the booster dose with an mRNA vaccine appear to be somewhat lower than after the second dose. Some people with confirmed myocarditis or pericarditis may choose to receive another dose after discussing the risks and benefits with their health care provider.

We've seen a small number of reports of people developing this rare disorder after receiving a COVID-19 mRNA vaccine.

Bell's palsy is an episode of facial muscle weakness or paralysis. Symptoms appear suddenly and generally start to improve after a few weeks. This condition generally affects nerves on one side of the face.

In the majority of cases, it's temporary. However, in very rare cases, Bell's palsy can be permanent.

Contact your health care provider if you have any of these symptoms:

• mild weakness to total paralysis on one side of the face, affecting facial muscle movement, such as:
  • smiling
  • squinting
  • blinking or closing the eyelid, which may result in tearing from the eye
• headache
• loss of feeling in the face
• hypersensitivity to sound in the affected ear
• loss of the sense of taste on the front two-thirds of the tongue

The symptoms of Bell's palsy may look like other conditions or medical problems. Always see your health care provider for a diagnosis.

Blood clots with low levels of blood platelets that occur after vaccination with viral vector vaccines (AstraZeneca Vaxzevria/COVISHIELD and Janssen Jcovden) are rare but serious.

These serious side effects have been reported to begin up to about a month after vaccination. Quick diagnosis and treatment is critical to reduce the risk of negative outcomes.

Seek immediate medical attention if you experience any of the following symptoms:

• shortness of breath
• chest pain
• persistent abdominal pain
• blurred vision
• confusion or seizures
• severe, persistent or worsening headache
• skin bruising or tiny blood spots under the skin (sometimes away from the part of your body the needle went in)

About the condition

Scientists and doctors are still working to understand this condition involving blood clots (thrombosis) with low platelets (thrombocytopenia). The condition is being referred to as thrombosis with thrombocytopenia syndrome (TTS).

If blood tests are positive for antibodies that affect platelets, this condition is also being called vaccine-induced immune thrombotic thrombocytopenia (VITT).

Thrombosis with thrombocytopenia syndrome is different from more common blood clotting issues, such as deep vein thrombosis or pulmonary embolism.

With thrombosis with thrombocytopenia syndrome, blood clots can form in different parts of the body, including the brain (called cerebral venous sinus thrombosis) and in the abdomen.

Thrombosis

This is a blood clot, which prevents blood from flowing normally.

Thrombocytopenia

This is a condition in which you have a low blood platelet count.

Platelets (thrombocytes) are blood cells that help blood clot. Platelets stop bleeding by clumping and forming plugs in injured blood vessels. Low platelets may lead to the bruising, which can be seen with thrombosis with thrombocytopenia syndrome.

Learn more about:

• Causality assessment findings: Thrombosis with thrombocytopenia syndrome

A very small number of reports of this rare condition have been reported following vaccination with the AstraZeneca Vaxzevria/COVISHIELD and the Janssen Jcovden vaccine. Some of the reports reviewed were in individuals who have had this condition previously.

Capillary leak syndrome is very rare, but can be serious. The condition causes fluid leakage from small blood vessels (capillaries). This can result in:

• low blood pressure
• swelling, mainly in the arms and legs
• sudden weight gain

If you have any of the above symptoms in the days after vaccination, you should seek medical attention immediately. You shouldn't get the AstraZeneca Vaxzevria/COVISHIELD or the Janssen Jcovden viral vector vaccine if you've previously experienced capillary leak syndrome.

There are a small number of reports of people who have developed this rare disorder after receiving the COVID-19 viral vector vaccine.

Guillain-Barré syndrome is a rare neurological disorder that causes the body's immune system to damage nerve cells. This can result in:

• pain
• numbness
• muscle weakness, progressing to paralysis in the most severe cases

Most people fully recover from the disorder. Seek medical attention right away if you have any of these symptoms after getting vaccinated. Symptoms can start between 3 and 25 days after vaccination.