This mother lost her one-month old baby to whooping cough. And now she's being targeted by anti-vaxxers.

The mother of a baby who died of whooping cough at just four weeks of age is being targeted online by anti-vaxxer trolls.

Catherine Hughes, lost her son Riley last Tuesday due to complications arising from whooping cough.

Riley was 32 days old.

Since his death, Hughes has spoken out about the importance of vaccination, having learned that a simple booster shot may have saved her son’s life.

The advice to pregnant women that came too late to save Riley Hughes.

She has received widespread support online, with many mothers sharing their own stories of loss, while also raising more than $37,000 for vaccine awareness through the Light For Riley Facebook page and Everday Hero campaign.

Unfortunately, she has also unwittingly become the target of trolls who have been inundating her with Facebook messages asking why her son wasn’t vaccinated.

“To all the strangers sending me Facebook messages and asking why my son wasn’t vaccinated. He was 4 weeks old! Too young to be vaccinated! Go learn something about immunisation and stop bothering me,” she wrote.

“Our whole family was vaccinated but we live in the state with the worst vaccine rates and sometimes family vaccination just isn’t enough to protect our babies.”

Both Catherine and her husband Greg were vaccinated against whooping cough and she had been told that a booster vaccine she had received three year’s previously would be sufficient to protect her newborn. Tragically, it wasn’t.

Catherine has now been informed that if she had received another shot in her third trimester, Riley may still be alive.

“Had I been advised, I would have had this booster while pregnant with Riley. Instead, I am left a heartbroken mum,” she told Mamamia.

The WA government confirmed on Thursday that they will offer free whooping cough vaccinations to pregnant women following recommendations from The Australian Technical Advisory Group on Immunisations.

The start date of the two-year program has yet to be determined, but a $600,000 commonwealth fund will pay for it.

The NSW government will also be participating in the trial.

Journalist Jane Hansen and Toni McCaffery — a woman who  also lost her daughter Dana to whooping at four weeks — have been campaigning for the changes and summed up the issues on Mornings.