TWO years ago Aussie doctor Rachel Heap penned a few words to promote the importance of vaccinating children.

Dr Heap, an intensive care specialist from NSW, is a fierce pro-vaccination campaigner who spends a lot of her spare time working to correct “misinformation” spread by anti-vaxxers.

She shared the words she penned on the Northern Rivers Vaccination Supporters website, a group she helped establish.

Her words were subsequently picked up, framed and posted in a Colorado doctor’s office.

That’s where Sunni Mariah saw it. She took a photograph of the sign and shared it to her Facebook page.

It has since gone viral. Her post has attracted 8.8k comments and has been shared over 190k times. News websites around the globe have picked the story up, with some commenting that the sign “throws serious shade at anti-vaxxers”.

Unsurprisingly, the sign sparked some lively debate online.

Nurse Linda Rau supported the sentiments of the sign, writing “just listen to one baby with whooping cough and you’ll never forget it.”

Nancy Kusisto Hansen wrote “I really think this sign should be in all doctor’s offices.”

Artemis Meyers disagreed, writing “here is my 2 cent (sic). If your children are vaccinated then what danger does my kid bring to yours? My child is my responsibility not yours, not the doctors, and not the government,” to which someone responded “it’s the babies too young to vaccinate who are really at risk with your thought process.”

When contacted about the sign’s new-found popularity, Dr Heap told Mamamia “the ghosts of the people that I’ve looked after keep driving me.”

Those “ghosts” are her patients who have been affected by vaccine-preventable diseases.

In a six-month stint working in a kids’ intensive care unit, Dr Heap looked after babies with whooping cough. One baby spent six months in intensive care, and may have been left with permanent brain damage.

“The other one didn’t make it,” she tells Mamamia.

On the NRVS website, Dr Heap further explains why she is so passionate about promoting vaccination.

“There is a prayer out there that says ‘Grant me the serenity to accept the things I cannot change, the courage to change the things I can, and wisdom to know the difference’ and there is also an expression in safety management that says ‘something is only as safe as the issue you are prepared to walk past’”, she writes.

“After my time working in the paediatric Intensive Care Unit, I decided that the fight to increase vaccination rates was something I would not walk past without at least trying to help.

“My approach has been to try and help my community, and those further afield, understand why vaccine preventable diseases are bad, and that vaccines are the safest and most effective way to protect everyone from them.”