Second dose mRNA vaccine after a first dose of AstraZeneca

AstraZeneca is a 2-dose vaccine. You need a second dose to be fully vaccinated. Being fully vaccinated means that you will have better protection against COVID-19 illness. It also gives you better protection against new variants of the virus, including the Delta variant. 

If you had your first dose of the AstraZeneca vaccine, you should get a second dose of the same vaccine.

Millions of people have been given 2 doses of the AstraZeneca vaccine. There is a lot of research about the safety and effectiveness of 2 doses of this vaccine.

Read more about getting your second dose of the AstraZeneca vaccine

mRNA vaccine after first dose of AstraZeneca

Some people have decided not to get a second dose of the AstraZeneca vaccine. In very rare situations, people had a severe side effect after the first dose of the AstraZeneca vaccine. These people have been told not to get a second dose of this vaccine. 

If you had a first dose of the AstraZeneca vaccine and you do not want a second dose of AstraZeneca, you can choose to get an mRNA COVID-19 vaccine dose instead. This will mean that you are fully vaccinated.

mRNA vaccines available in Ireland are the Pfizer/BioNTech and Moderna COVID-19 vaccines.

How to get an mRNA vaccine for your second dose

If you want to get an mRNA vaccine after having 1 dose of the AstraZeneca vaccine, you can go to a:

  • Pfizer dose 2 walk-in vaccination clinic
  • Moderna dose 2 walk-in vaccination clinic

Walk-in vaccination clinics are in different locations. You can go to any dose 2 walk-in clinic, it does not have to be near your home. Most dose 2 walk-in clinics will be offering the Pfizer vaccine.

You should get either the Pfizer or Moderna vaccine at least 28 days after getting your first dose of AstraZeneca.

Bring your vaccination card that shows you have had 1 dose of the AstraZeneca vaccine.  

You will be fully vaccinated:

  • 7 days after your Pfizer/BioNTech dose
  • 14 days after your Moderna dose

Getting 2 different vaccines

You can choose to get an mRNA vaccine as your second dose after having one dose of the AstraZeneca vaccine. This has been approved by the National Immunisation Advisory Committee (NIAC) in Ireland. 

But getting 2 different vaccines has not been approved and licenced by the European Medicines Agency (EMA) yet. The EMA has approved using 2 doses of the same COVID-19 vaccine only. 

We have less information about the safety of getting 2 different COVID-19 vaccines compared with having 2 doses of the same vaccine. 

So far, there have been no concerns about serious side effects with this option. 

Some studies have found that side effects are more common than when 2 doses of the same vaccine are used. 

These include:

  • pain where the injection was given
  • headache
  • muscle aches
  • tiredness
  • chills and fever

Read about the side effects of the Pfizer/BioNTech and Moderna COVID-19 vaccines.


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

Last updated: 2 September 2021 at 3.20pm