Side effects - AstraZeneca COVID-19 vaccine

Like all medicines, vaccines can cause side effects. Most of these are mild to moderate and short-term. Not everyone gets side effects.

If you are concerned about side effects, phone your GP for advice.

The official name of AstraZeneca's COVID-19 vaccine is 'Vaxzevria'. But most people call it 'AstraZeneca'.

Common side effects

The common side effects after the AstraZeneca vaccine are more likely after the first dose of the vaccine.

People aged 65 and older are less likely to experience common side effects.

More than 1 in 10 people may experience:

  • feeling tired
  • tenderness, bruising, pain or itching in the arm where you had the vaccine injection
  • headache
  • muscle pain
  • joint pain
  • nausea
  • fever (temperature of 38 degrees Celsius or above)

More than 1 in 100 people may have:

  • redness or swelling where you had the injection
  • diarrhoea
  • vomiting
  • a low platelet count (that doesn’t cause any symptoms)

Rare side effects

More than 1 in 1,000 people may experience:

  • reduced appetite
  • dizziness
  • sleepiness
  • sweating
  • swollen lymph glands
  • rash

Very rare side effects

Very rare side effects of the AstraZeneca vaccine include:

Very unusual blood clots

Very rarely people may develop very unusual blood clots with low platelets after this vaccine. The risk of this very rare condition is higher in younger people.

It is seen in approximately:

  • 1 in 100,000 people aged 50 and over
  • 1 in 50,000 people aged 18 to 49

1 in 5 people who develop this condition may die.

These blood clots are less likely to be reported after the second dose of the vaccine.

Your GP, doctor or the person giving you your vaccine can advise you on the risks and benefits of getting this vaccine. 

Even though these side effects are very rare, you should know the symptoms to look out for.

Symptoms of very rare blood clots

Get urgent medical help if you get any of these symptoms in the weeks after the AstraZeneca COVID-19 vaccine:

  • breathlessness
  • pain in the chest or stomach
  • swelling or coldness in a leg
  • severe or worsening headache (particularly 3 or more days after the vaccine)
  • blurred vision
  • confusion
  • seizures
  • persistent bleeding, under the skin where there was no previous injury
  • multiple small bruises, reddish or purplish spots, or blood blisters under the skin

Most people who got these very rare side effects got them within 14 days of getting the AstraZeneca vaccine.

No need to take aspirin

You do not need to take aspirin before or after vaccination. These are very rare blood clotting conditions with low platelets. Aspirin would not have a beneficial effect.

You should continue to take any prescribed medication unless told otherwise by your GP.

Capillary leak syndrome

A very small number of people in Europe have experienced capillary leak syndrome after getting the AstraZeneca vaccine.

Capillary leak syndrome is a rare but serious condition. It can sometimes be fatal.

Do not get the AstraZeneca vaccine if you have previously had capillary leak syndrome.

Get urgent medical help if you have had an AstraZeneca vaccine in the past few days and you notice:

  • rapid swelling of your arms or legs
  • sudden weight gain

You may also feel faint due to low blood pressure.

These are symptoms of capillary leak syndrome.

Other side effects

Guillain-Barré syndrome (GBS)

GBS is a rare and serious condition that affects the nerves. Symptoms can range from mild weakness to severe paralysis (being unable to move a part of your body). Most people eventually fully recover even from the most severe symptoms. Some may continue to experience weakness.

Getting GBS after having the AstraZeneca vaccine is very rare. Only a small number of people have reported getting the condition after being vaccinated. We don't know yet if the vaccine is linked to GBS or not.

You should know the symptoms to look out for in the weeks after being vaccinated.

Get urgent medical help if you develop:

  • double vision or difficulty moving your eyes
  • difficulty swallowing, speaking, or chewing
  • co-ordination problems and unsteadiness
  • difficulty walking
  • tingling sensations in your hands and feet
  • weakness in your arms, legs, chest or face
  • problems with bladder control and bowel movements

Serious side effects

Serious side effects, like a severe allergic reaction, are extremely rare.

Your vaccinator is trained to treat any serious allergic reactions.

You should not get another viral vector vaccine if you have had a severe allergic reaction to the AstraZeneca vaccine, any of its ingredients, or have been told by your doctor not to have the AstraZeneca vaccine.

Viral vector vaccines currently being offered in Ireland are the AstraZeneca vaccine and the Janssen vaccine.

Read more about mRNA and viral vector vaccines

Fever after COVID-19 vaccines

It’s common to develop a fever (temperature of 38 degrees Celsius or above) after any vaccination. This usually happens within 2 days (48 hours) of getting the vaccine. It usually goes away within 2 days.

You are more likely to get a fever after the first dose of this vaccine.

If you feel uncomfortable, take paracetamol or ibuprofen. Follow the instructions on the box or leaflet. Do not take ibuprofen if you are pregnant.

If your fever starts more than 2 days after you are vaccinated, or lasts longer than 2 days, you should self-isolate (stay in your room). Phone your GP to arrange a COVID-19 test.

If you develop COVID-19 symptoms after your vaccine

COVID-19 vaccines cannot give you COVID-19.

It is possible to get COVID-19 before getting your vaccine and not realise you have the symptoms until after your vaccination.

If you have symptoms after the first dose of your COVID-19 vaccine, you still need to have the second dose. While you may get some protection from the first dose, having the second dose will give you the best protection against the virus.

Self-isolate and phone a GP to arrange a COVID-19 test if you have a fever which:

  • starts more than 2 days after you get your vaccine
  • lasts longer than 2 days after you get your vaccine

If you have any common symptoms of COVID-19, it's important to self-isolate (stay in your room) and arrange a test to find out if you have COVID-19.

Read about what happens during the COVID-19 test

Updates on COVID-19 vaccine side effects

The COVID-19 vaccines have gone through the same clinical trials and safety checks as all other licensed vaccines. But these vaccines are new and long-term side effect information is limited.

As more people in Ireland and around the world get vaccinated, more information on side effects may become available.

We will update this page with any new information.

Reporting side effects of COVID-19 vaccines

As with all vaccines, you can report suspected side effects to the Health Products Regulatory Authority (HPRA).

There are 2 ways you can report a suspected adverse reaction to a COVID-19 vaccine:

As much information as is known should be provided, and where possible, the vaccine batch number should be included. You'll find this on your vaccine record card.

You can also ask your doctor or a family member to report side effects for you.

The HPRA cannot provide clinical advice on individual cases. Talk to your doctor or pharmacist about any medical concerns you may have.

Read more about reporting vaccine side effects to the HPRA

This content was fact checked by vaccine experts working in Ireland.

Last updated: 27 July 2021 at 11am