Northland Health is worried anti-vaccination campaigners are spreading false information about meningococcal disease.
The health board is running a mass vaccination campaign to stem an outbreak of meningococcal C that has killed three people since July.
It aims to vaccinate 36,000 young people but so far only 7000 have had their free injections.
Medical Officer of Health Clair Mills says some dangerously incorrect information about the vaccine and possible alternatives is circulating.
She says parents weighing up the options need to be clear that even the British Faculty of Homeopathy has advised that homeopathic treatment offers no protection against meningococcal C.
Dr Mills says the vaccine is used routinely overseas and has been proved safe and effective.
Northland Health says parents can rely on the safety of the vaccine.