Human Papillomavirus (HPV) describes a group of around 100 viruses, although most of them are not dangerous. These viruses are common with most people getting the virus at some stage in their life, and usually the immune system alone is enough to fight them off. Certain types of HPV belong to a high-risk group due to their ability to cause genital warts and abnormal cell changes which can lead to cancer. Cancers linked to HPV include cancers of the cervix, anus, penis, vagina, and certain other cancers in the head and neck.

The HPV vaccine protects against the types of HPV which are known to cause cancer. The vaccine used, under the brand name Gardasil, contains highly purified strains of HPV type 6,11,16 and 18 which are the strains most likely to cause cancers.