Vaccines teach your immune system how to protect you from diseases.
It is much safer for your immune system to learn how to protect you from COVID-19 through vaccination than by catching the virus.
We do not know yet how long immunity will last. Clinical trials are ongoing to find this out.
How long it takes to work
It takes 3 weeks after getting the first dose for the AstraZeneca COVID-19 vaccine to start to work.
You should get your second dose 12 weeks after your first dose. It takes 15 days after getting the second dose to have the best protection.
Protection from COVID-19
After having both doses of a COVID-19 vaccine, most people will be protected against the virus.
There is a small chance you might still get COVID-19 after vaccination. Even if you do get COVID-19, being vaccinated can reduce how serious your symptoms will be.
There is some new evidence to show that the vaccines may reduce you spreading COVID-19 to other people but more research is needed.
The HSE, Department of Health and the World Health Organization recommends that you get your COVID-19 vaccine when it is offered to you.
Even after you are vaccinated, continue to follow public health advice on how to stop the spread of COVID-19. For example, social distancing, wearing a face covering and washing your hands properly and often.
If you take immunosuppressive medicines
If you have a weakened immune system, your COVID-19 vaccine may not work as well for you. But there is no extra risk in getting it.
Testing and evidence
The AstraZeneca vaccine has been tested on people aged 18 and older.
In clinical trials, the vaccine reduced the risk of people:
- getting COVID-19 by 60%
- being hospitalised with severe COVID-19 by 100%
People aged 70 and older
People aged 70 and older had the same immunity as other age groups. But the AstraZeneca vaccine was tested on very few older people. Clinical trials are ongoing to show how well it works in more people aged 70 and older. Until we have those results, the AstraZeneca vaccine will not be given to people aged 70 years and older. They will get the Pfizer/BioNTech or Moderna vaccines instead.
New evidence from England shows that the vaccine reduced the risk of people getting COVID-19 by:
- 76% after the first dose for up to 12 weeks
- 82% when the second dose was given 12 weeks later
New evidence from Scotland shows:
- the risk of being admitted to hospital with severe COVID-19 is reduced by 94%, 4 to 5 weeks after 1 dose of the AstraZeneca vaccine
Use of AstraZeneca COVID-19 vaccine restarted
Use of the AstraZeneca COVID-19 vaccine has been restarted after a short pause.
The AstraZeneca COVID-19 vaccine is safe and effective. Go to your appointment if this vaccine is offered to you.
This content was fact checked by vaccine experts working in Ireland
Last updated: 29 March 2021 at 12pm