Teenagers and other eligible individuals under the age of 25 will now be offered one dose of the human papillomavirus (HPV) vaccine instead of two, according to an announcement from the UK Health Security Agency today. From September, those aged 12 to 13 years old, as well as eligible gay, bisexual and other men who have sex with men (GBMSM), will receive one dose of the vaccine which is used to protect against HPV-related cancers.