Mistruths and propaganda are behind the recent slide in vaccination rates across the country.
That's according to the HSE's Assistant National Director for Public Health Dr Kevin Kelleher.
Figures obtained by The Irish Times show vaccination rates have dropped to as low as 81% in some parts of the country.
Dr. Kelleher says it's not just traditionally poorer areas that are affected, as "widely discredited myths" are taking hold.
"Some of the more prosperous parts of urban areas like Dublin and other places, their rates are not as high as well. The whole of Wicklow is one of the worst areas, places like Bray," he said.
"Some intimation is that people are being influenced by some of the less scrupulous messages that are appearing on social media about vaccines - using stories that have been repeatedly discredited, but they still pop up."