The giant hole being left by Ashley Bloomfield at the top of the Ministry of Health is getting larger, with two top public health leaders also leaving this week.

This follows the director general of health's surprise resignation that was announced earlier today, with his last day at the end of July.

The ministry is also having farewells this week for director of public health Dr Caroline McElnay, and public health deputy director Dr Niki Stefanogiannis.

Burnout is thought to have played a major role in their decisions to leave, and it's a factor that is being felt across the whole health sector, along with Covid-fatigue.

Uncertainty about upcoming health sector reforms may also have been a factor, with the ministry being moved into a strategy and monitoring role while Health NZ will run the health system.

The departures of Bloomfield, McElnay, and Stefanogiannis raise questions about what impact their vacancies will have in a pandemic that shows no sign of ending, with possible resurgences in cases in coming months, including over winter, and new variants inevitably arriving here.

Bloomfield has already said, however, that he is confident in the systems and processes in place to respond to the pandemic after he leaves.

The ministry has been approached for comment.

McElnay, whose last day is tomorrow and whose resignation was announced to ministry staff in February, has regularly fronted press conferences throughout the pandemic, usually when Bloomfield has been away.

• 'Worked tirelessly to keep New Zealanders safe': Ashley Bloomfield resigns

Dr Caroline McElnay has resigned as director of public health. Photo / Mark Mitchell

She is expected to announce her leaving while fronting the 1pm Covid-19 press conference tomorrow.

McElnay plans to spend the next six months travelling, according to a ministry email obtained by the Herald and written by deputy director general of population health Deborah Woodley.

"After five years in the role of director of public health – and five years of commuting from her Napier home – Caroline has decided the time is now right for her to explore new opportunities and, initially, a wonderful six months of travel with her husband," Woodley said.

"Along with many others in the health sector she has worked tirelessly, sacrificing many nights, weekends and weeks away from family to ensure that throughout our response, there has been strong, clear public health advice which has kept us all safe."

Woodley thanked McElnay for her "incredibly hard work", her "selfless, mature" leadership, and "her ability to remain calm and composed whilst under enormous pressure".

"Caroline is highly respected by her team, her colleagues – both within the Ministry and the broader sector, and by ministers. She has worked hard to ensure a collaborative effort across the public health system and in particular, she has supported our public health units to achieve new ways of working at a systems level."

The country's 12 public health units had no way of sharing details with each other at the start of the pandemic unless officials made phone calls to each other. A national system was set up quickly so critical details could be more easily shared, as well as the workload.

Stefanogiannis' last day is on Friday.

Dr Niki Stefanogiannis' last day in the role of public health deputy director is Friday. Photo / Supplied

"Niki has decided it's time for a break and to spend some time with her family. We will miss her greatly," said a ministry email in February, obtained by the Herald, and written by McElnay.

"She has been a tower of strength to me personally and to the rest of the ODPH (public health team). She has dedicated herself to providing the very best public health advice on a wide range of topics over her time at the ministry but I would like to thank her especially for her hard work on the Covid response and for her support to our team and colleagues across the sector.

"It has been an incredibly busy two years and Niki is one of the heroes of our Covid response."

Earlier today Bloomfield said he had received positive feedback from the public, and while there were some vitriolic responses, much worse had been directed at female colleagues - though he didn't name anyone.

"I think that is terrible, and it's something we need to do something about."

He said he had been thinking about the right time to leave, but he still had "very mixed feelings because I work with amazing people".

Hitting "such high vaccination rates" had been a particular highlight, he said, including the high uptake for Māori and Pasifika aged 65 and older. He was also proud of the efforts to raise uptake among younger Māori, where coverage still lags well behind non-Māori.

Asked whether he had been asked to have a role in the new health system, which comes into effect on July 1, Bloomfield said he was "happy with the role I had" because it was where he could add the most value.

Dr Ashley Bloomfield's shock resignation on Wednesday was followed by news of the departure of two top public health officials. Photo / Mark Mitchell

He would also bed in the reforms as he was staying on as director general until July 29.

But it was also a very different role to the one he came into four years ago, and the timing was good for someone new to come in, Bloomfield said.

Covid-19 Response Minister Chris Hipkins said he was sad Bloomfield was leaving and he had saved thousands of lives.

But he was happy for him because he "thoroughly" deserved a break.

"Few would be able to say they've made a greater sacrifice than Dr Bloomfield."