Like all medicines, COVID-19 vaccines can cause side effects. Most do not last long. Not everyone gets side effects.
If you are concerned about side effects, contact your GP for advice.
Serious side effects, like a severe allergic reaction, are extremely rare. Your vaccinator is trained to treat allergic reactions.
Side effects of COVID-19 vaccines
The COVID-19 vaccine recommended for most people in Ireland is the Pfizer/BioNTech vaccine. It is a mRNA vaccine.
Most side effects from COVID-19 vaccination do not last long.
Fever after COVID-19 vaccines
It’s common to develop a fever (temperature of 38 degrees Celsius or above) after COVID-19 vaccination. This usually happens within 48 hours of getting a vaccine.
If you feel uncomfortable, take paracetamol or ibuprofen following the instructions on the box or leaflet.
Pfizer/BioNTech vaccine side effects
The Pfizer/BioNTech COVID-19 vaccine is called Comirnaty.
You can get some side effects with this vaccine.
Very common side effects
Very common side effects may affect more than 1 in 10 people.
These include:
- tenderness or swelling in your arm where you had the vaccine
- feeling tired
- headache
- muscle pain
- joint pain
- diarrhoea
- fever (temperature of 38 degrees Celsius or above)
- chills
Some of these side effects were slightly more frequent in young people age 12 to 15 than in adults.
In children age 2 to 4, the most common side effects include:
In children age 6 to 23 months, the most common side effects include:
- irritability
- sleepiness
- loss of appetite
- tenderness or redness at the injection site
- fever (temperature of 38 degrees Celsius or above)
Common side effects
Common side effects may affect up to 1 in 10 people.
These include:
- nausea
- vomiting
- redness in your arm where you had the vaccine
- swelling of the lymph glands
For children age 6 months to under 2 years, common side effects includes:
Uncommon side effects
Uncommon side effects may affect up to 1 in 100 people.
These include:
- feeling unwell
- pain in the arm where you had the vaccine
- sleeplessness
- itchiness where the vaccine was given
- allergic reactions like rash or itchiness in general
- a rash
- excessive sweating
- night sweats
- decreased appetite
- lethargy, asthenia (lack of energy) and malaise (feeling unwell)
- dizziness
Rare side effects
Rare side effects may affect up to 1 in 1,000 people.
These include:
- an allergic reaction that can cause hives or swelling of the face
- weakness in the muscles on one side of your face (that may cause it to droop temporarily)
Very rare side effects
Very rare side effects may affect up to 1 in 10,000 people.
These include:
Myocarditis and pericarditis are inflammatory heart conditions.
The risk of these very rare conditions is higher in young men.
These conditions are more likely to happen after the second dose of the primary course of the vaccine. They have mostly been seen within 14 days of getting the vaccine.
The risk of myocarditis is lower after a booster dose.
Symptoms of myocarditis and pericarditis
Get urgent medical help if you get any of these symptoms in the weeks after the Pfizer/BioNTech vaccine:
- breathlessness
- palpitations (a forceful heartbeat that may be irregular)
- chest pain
Signs of myocarditis in younger children may be more general including:
- irritability
- vomiting
- difficulty feeding
- rapid and shallow breathing
- fatigue
Extremely rare side effects
We do not know yet how many people are affected by extremely rare side effects. There is not enough data available at this time.
Extremely rare side effects include:
- a severe allergic reaction (anaphylaxis)
- extensive swelling of the limb where you got your vaccine
- tingling or prickling sensation, or loss of sensation in some part of the body
- people who have had facial fillers may develop swelling of their face
- erythema multiforme - a skin reaction that causes red spots or patches on the skin. It may look like a target or 'bulls-eye' with a dark red centre surrounded by paler red ring
- heavy menstrual bleeding (periods)
Ingredients of Pfizer/BioNTech COVID-19 vaccine
The Pfizer/BioNTech COVID-19 vaccine does not contain eggs, preservatives or latex.
You can read more about the vaccine ingredients on the European Medicine Agency's website.
Comirnaty (Pfizer/BioNTech) COVID-19 vaccine - ema.europa.eu
Who should not get this vaccine
Most people can safely get the Pfizer/BioNTech mRNA COVID-19 vaccine.
Who should not get the Pfizer/BioNTech COVID-19 vaccine
This vaccine is not recommended if you:
- had a severe allergic reaction to a previous dose of this vaccine or another mRNA vaccine
- had a severe allergic reaction to any of the ingredients in this vaccine - including polyethylene glycol or PEG
- were told by a doctor that you should not get an mRNA vaccine
- have had a severe allergic reaction to Trometamol (one of the contents in contrast dye used in MRI radiological studies)
Talk to your doctor before getting this vaccine if you:
- had a severe allergic reaction (anaphylaxis) in the past, including to any other vaccine or medicine
- had myocarditis or pericarditis (inflammation of the heart muscle) after a previous dose of any COVID-19 vaccine
- have mastocytosis
- have a child with a history of multisystem inflammatory syndrome (MIS-C), also known as PIMS
Other COVID-19 vaccines
The Pfizer/BioNTech COVID-19 vaccine is an mRNA vaccine. Some people may not be able to get an mRNA vaccine or chose not to get one. In this case, the Nuvaxovid (Novavax) vaccine is usually recommended.
Nuvaxovid (Novavax) vaccine
The Nuvaxovid (Novavax) vaccine is currently not available in Ireland.
We are trying to get supplies of the vaccine but we do not know if or when it will become available.
You can call HSELive at freephone 1800 700 700 and ask to be contacted when the Nuvaxovid (Novavax) vaccine becomes available.
Vaccines previously offered
Side effects of COVID-19 vaccines previously offered in Ireland.
Reporting side effects
If you think you or your child have had a side effect after receiving a vaccine, you can report it to the Health Products Regulatory Authority (HPRA).
Your GP, nurse, pharmacist or a family member can also report the side effect to the HPRA.
COVID-19 vaccine adverse reaction report - hpra.ie
When reporting a side effect
Give as much information as possible. Include the vaccine batch number if you have it. You'll find this on your vaccine record card.
The HPRA cannot provide clinical advice on individual cases. Talk to your doctor or pharmacist about any medical concerns you may have.
Mpox vaccine
If you recently had the mpox vaccine, wait 4 weeks before you get vaccinated with any COVID-19 vaccine. This is a precaution because of the unknown possible risk of myocarditis.
This content was fact checked by vaccine experts working in Ireland.