The changes, which follow last year's resignation of former NHS president and CEO Debbie Sevenpifer, were needed to put a new team in place to oversee reforms, said Kevin Smith.
"It was really a number of issues, including expanding the skill set of the management team and the importance of bringing in some new blood that will also help us address some of the challenges that the organization is having," Smith said in an interview.
"It certainly had nothing to do with the performance of the individuals, but was really about where the organization was going."
The NHS did not name the individuals who left, but The Canadian Press obtained a copy of a Jan. 11 memo from interim president and CEO Sue Matthews in which she announced the departures of two vice-presidents.
It was not clear from the memo if Anne Atkinson, vice-president patient services, and Bala Kathiresan, executive VP and COO, were fired or left voluntarily. Employment contracts show the two would be entitled to a minimum of six months of salary in severance. They were paid between $225,000 and $265,000 a year.
The NHS confirmed four other members of the management team are also gone, but did not provide names.
However, The Canadian Press has learned they were: Tracy Davey, director of the Greater Niagara General Hospital, Tracy Fattore, regional director of quality, risk and patient safety, Jane Cornelius, health program director for critical care and emergency at the NHS and Dan Belford, clinical manager at St. Catharines General.
Progressive Conservative Leader Tim Hudak, who represents Niagara-West Glanbrook, welcomed the changes at the NHS, but said more were needed to restore public confidence in the hospitals.
"It’s a good start, but a long time coming," Hudak told reporters.
"That thing has been a terrible mess that the Liberals let fester for years and years, but the job ain’t done yet, not by a long shot."
Welland New Democrat Cindy Forster said the biggest worry is more local hospital services will be reduced and concentrated in the biggest city in Niagara.
"(We have) concerns the existing full service hospitals like Welland and Niagara Falls will actually lose some of their services ... with the majority of services moving to St. Catharines, which is in the northern end of the Niagara Peninsula," said Forster.
Smith said he expects to remain as the supervisor of the NHS until late this year, when he will have hired a new management team and permanent CEO to lead needed changes. He also promised to consult the local community on which services hospitals should provide.
However, he cautioned that people must be prepared for change and can't just ask for more hospitals and more services.
"We know we will have to make some changes in where and how we deliver services," said Smith.
"So we’re really working through how do you do that kind of consultation that’s meaningful, but also that keeps it to some viable outcomes. The evidence is pretty clear it’s actually about fewer sites, with more focus and increasingly working on flow and capacity and clinical integration."
The NHS, which includes seven hospitals in St. Catharines, Niagara Falls, Niagara-on-the-Lake, Fort Erie, Welland and Port Colborne, has been under the control of the government-appointed supervisor since last summer.
The hospitals have been under intense criticism after closing some emergency rooms, which prompted a coroner's inquest into the death of a teen who was taken by ambulance past a closed emergency department to one further away.
During last fall's election campaign, the NDP pledged to re-open the closed emergency rooms in Fort Erie and Port Colborne.
Hudak also called Thursday to have the two emergency rooms re-opened.
The NHS also came under fire last October when an 82-year-old woman who fell and broke her hip in the entrance area of the Greater Niagara General Hospital was told to call an ambulance for help.
Former NHS chief information officer Christine Clark left last July amid a controversy over the release of information about the deaths of patients during a C. difficile outbreak that killed 33 people.