Human Papillomavirus (HPV) Vaccination

HUMAN PAPILLOMAVIRUS (HPV) VACCINATION

Human papillomaviruses (HPV) are a group of viruses that infect squamous epithelia, including the skin and mucosal surfaces of the upper respiratory and anogenital tracts. Approximately 100 types of HPV have been identified, of which around 40 infect the genital tract. The majority of genital infections are asymptomatic but in some cases may be associated with genital warts and (the reason for the development of the HPV vaccine), cervical cancer. The time between infection and development of cancers may range from 12 months to over 10 years. It is important to note that HPV is associated with genital and anal cancers in both men and women and also with cancers of the mouth and throat. Importantly, not all types of HPV are carcinogenic; the risk of cancer development associated with different strains is variable and HPV viruses that cause warts (a common sexually transmitted infection) may be low risk for carcinogenicity and in some cases strains are not considered carcinogenic. Genital HPV infections are transmitted primarily through sexual intercourse with infected individuals and the use of condoms reduces the risk of sexual transmission. HPV may also be transmitted vertically from mother to child. Persistent HPV infection with HPV 16 and HPV 18 (high-risk strains) is associated with the majority of cervical cancers. There are however, strains other than HPV 16 and HPV 18 that are carcinogenic.

The HPV vaccine comprises recombinant subunits expressed in yeast or in cells of insect origin such that the vaccine contains non-infectious, virus-like particles. The current UK vaccine, Cervarix, affords protection against HPV 16 and HPV 18 and is very effective at preventing precancerous lesions associated with these virus strains for at least 6 years, probably longer. Since the main aim of the HPV vaccine programme is to reduce the incidence of cervical cancer, the vaccine is currently administered to females (not males) between the age of 12 and 13 with a catch-up programme for older females up to the age of 18.