The Save Navan Hospital Campaign group has said it is "disheartened" by the decision to close the hospital's emergency department, but added it "won't give up without a fight".
The HSE confirmed today that the emergency department will close at Our Lady's Hospital in Navan.
It will be replaced by a GP referred 24 hour medical assessment unit and an injury unit.
The intensive care unit will also close under the plan.
"We're not going to give up without a fight. We are going to mobilise again like we did before" said Noeleen Donoghue, Secretary of the Save Navan Hospital Campaign group.
She said the closure will have a huge impact on the people of Meath.
"Anybody who will possibly need healthcare in the future will suffer from this," she said.
"We know from the past, that people can’t get to see a GP so where are they going to go?
"Hospitals in Dublin and Drogheda are under pressure. It’s just crazy to think that’s where they’re going to send patients."
The HSE said the move is supported by the senior clinicians working in the hospital, who have all expressed concerns about patient safety in the ED.
Once established, the medical assessment unit will operate 24/7 and will continue to see around 80% of the 25-30 patients who currently arrive at the hospital's emergency department.
However, clinically unstable patients will no longer be brought to Navan.
The HSE has said that on average, five or six more unstable patients per day who are currently brought to the hospital, will now be sent directly to another hospital.
From 30 June, the HSE said there will be greater transfer of patients between Our Lady's Hospital Navan and Our Lady of Lourdes Hospital Drogheda, where two additional ICU beds will open by September.
Clinical Director of Our Lady's Hospital Navan and consultant surgeon Gerry McEntee said that critically ill patients in Co Meath will now be provided with the best opportunity of survival by being brought directly to the nearest Model 3 or 4 hospital.
Earlier, the Minister for Health and senior HSE management met TDs and Senators from Co Meath to discuss the future of the hospital.
In 2013, Navan was included in a list of ten hospitals earmarked for ED closure and a report recommended they be downgraded to medical assessment units or injury units.
All the emergency departments on that list are now closed, except for Our Lady's Hospital, part of the Ireland East Hospital Group.
Additional reporting: Sinead Hussey
