Those aged between 30 and 39 can now avail of a COVID booster shot from today.
Anyone aged 16-29 can also receive a booster if they were administered the Janssen vaccine as their primary dose.
"We encourage everyone to avail of your booster dose when offered as it gives you the best protection from serious illness caused by Covid-19," the HSE said in a statement.
Anyone due for a booster will receive an appointment by text message from the HSE or can attend a designated walk-in clinic. Appointments can also be booked online. Some GPS and pharmacies are also administering boosters.
To attend an appointment you must bring photo ID and proof of your date of birth. Healthcare workers should bring proof of their employment.
At least three months should have passed since receiving the final shot of your primary dose before you can receive the booster. If you tested positive for COVID in the past, at least three months should have passed since your test result before taking the booster.
The HSE has reported already beginning to feel the pressure of the Omicron surge.
"We’re seeing some of our sites challenged now in terms of beds not being able to open as a result of staffing challenges," said HSE chief operations officer Anne O’Connor.
Tánaiste Leo Varadkar has said he expects the Omicron wave to pass quicker than previous waves, and believes it will peak in the next week.