The latest Ministry of Health figures show 73 schools have refused to take part in the free school HPV immunisation programme, which protects against cervical and genital cancers and some forms of head and neck cancer.
This could mean thousands of children are missing out.
But those figures are from 2009 - just a year after the HPV programme began and seven years before it was extended to boys.
Meanwhile a nationwide shortage of the vaccine means that some teenagers have been unable to have the second injection to complete their immunisation.
Lynn Freeman is joined by the Director General of Public Health Dr Caroline McElnay and Dr Helen Petousis-Harris, Research Director of the Immunisation Advisory Centre.