Speaking at an Irish Pharmaceutical Healthcare Association information event at the RCPI to mark world immunisation day, Mr Harris insisted the only people who should be giving medical advice are doctors and qualified experts.
He said there has been a growing trend of unqualified groups giving out vaccine misinformation, resulting in low uptakes of the HPV cancer vaccine and treatments for other conditions.
He said the “nonsense” being put forward by some people “with no medical qualification whatsoever” is putting vulnerable people at risk and must not be listened to by the public.
“The people who are qualified are doctors, scientists, the European Medicines Agency our medical community here in Ireland, and the World Health Organisation.
"What we have seen in recent times are people who are not doctors, not scientists, not medical experts, giving advice that runs counter to all the medical information available. That’s not harmless. That has a real impact.”