Dr Tony Holohan said the loss of his wife left him with the "desire to do something meaningful in her memory" as he steps down as CMO.
The top doctor was the face of the Covid response in Ireland over the last three years as he fronted press conferences and became the bearer of bad news.
Dr Holohan's wife Emer died in February of 2021 and has been cited by him as one of the reasons for his departure.
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In a lengthy statement the Dubliner said: "Today I stand down as CMO and leave the civil service. Together with the Department of Health, the HSE, and other health agencies, it’s been an honour to serve the Irish people, particularly through the Covid-19 pandemic.
" I believe that optimal public health and wellbeing, both physical and mental, is essential for people to reach their potential, and is key to a just and equitable society. Professionally I will continue to explore opportunities around health and related issues, but I want to see what else is out there too.
"There’s much to be done, especially with vulnerable groups, and now that I have more time, I plan to take on some pro bono work within healthcare and in wider community initiatives. The loss of my wife has also left me with a desire to do something meaningful in her memory, though the exact form it will take is still undecided. First though, after 22 years of a rewarding and enriching career in the civil service, I want to say thank you. Thank you to my colleagues in the Department of Health, government, the many agencies I worked with and the HSE.
"Having served seven Ministers, I witnessed firsthand just how dedicated each one of them has been. It has always impressed me. Thank you to the Irish people for their enormous trust, sacrifice, patience, and resilience in the last couple of years, and for their many kind messages when Emer died.
"I cannot adequately express how much this has meant to me and to our children. So many of us lost loved ones in the pandemic. My heartfelt commiserations to you all. And finally, of course, thank you to my friends and my family. They’ll be seeing a lot more of me for a while whether they like it or not! New adventures lie ahead."
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