People aged 55 and older can now register for a second Covid-19 booster vaccine.
Appointments can be made either through the Health Service Executive's vaccine portal, or with participating GPs and pharmacies.
The HSE said women who are more than 16 weeks pregnant can also book their next booster jab.
Children aged 5-11 who are immunocompromised, who are due their first booster, will be asked to register for this soon.
The HSE also said that from next week, people aged 50 to 54, can also register for a second booster vaccine, while anyone with long term health conditions will be offered boosters soon.
HSE Chief Clinical Officer Dr Colm Henry said: "Everyone aged over 55 and pregnant women, should now get their next booster dose.
"We know immunity tends to reduce after a period of months following your last vaccine so this booster will give ongoing protection from serious illness, and increase immunity against infection from Covid-19."
It comes as the number of people in hospital with Covid-19 continues to reduce.
As of 8am, there were 300 people in hospitals around the country with the virus, down seven on the same time yesterday, and down from 352 last Thursday.
There were 20 people in intensive care units as of 11.30am with Covid-19.
Vaccine inequality
Half of people in poorer countries have now received two vaccine doses against Covid-19, a global vaccine alliance said.
Gavi, which co-leads the Covax global vaccine distribution scheme with the World Health Organization (WHO) and others, said the 92 lower-income countries receiving donor-funded jabs had reached 50% coverage on average.
Gavi said governments had successfully prioritised the vaccination of healthcare workers, with most of the lower-income countries having vaccinated more than 80 percent of this highest-risk group.
Acting managing director of Gavi's Covax offic Derrick Sim hailed the "vital progress".
"The pandemic is not over," he said, pointing out that "cases and deaths continue to rise and new variants pose a threat to us all."
Earlier this year, UN Secretary-General Antonio Guterres said "vaccine inequity is the biggest moral failure of our times and people and countries are paying the price".
