Second COVID-19 booster doses are being offered to people aged over-65, and those with a weak immune system.
The Health Service Executive (HSE) says those eligible can book online for appointments at vaccination centres.
While participating GPs and pharmacies will begin giving second boosters in the coming weeks.
The booster is open to those aged 65 years and over, and people with a weak immune system aged 12 and over.
This follows guidance from the National Immunisation Advisory Committee (NIAC).
Appointments will be available from Friday, April 22nd.
Dr Colm Henry, Chief Clinical Officer at the HSE, says: "I am urging everyone in these groups to get this second booster dose.
"People being recommended this second booster are those most at risk of severe illness from COVID-19.
"It is important you get your second booster to help maintain your protection from becoming seriously ill or needing hospital treatment if you catch the virus."
People aged 12 years and older who have a weak immune system have previously had one additional dose of vaccine, and were also offered a first booster dose earlier in 2022.
Most people in this group are not yet due to have a second booster - the HSE says it will send text message reminders to people in this group as their second boosters become due.
If you are 65 or over, you should get your second booster at least four months after your first booster.
While people should only get a second booster dose at least four months after a positive COVID test result or when symptoms started.
Those attending for a booster should bring a photo ID such as a passport, driver's licence, Garda age card or student/school ID.