Paediatrician Recommends HPV Vaccination
Cervical cancer is the second most common cancer affecting women and the second leading cause of cancer death in women worldwide. It develops when abnormal cells in the lining of the cervix multiply beyond control in response to human papillomavirus. It is therefore the first ever identified cancer to be directly caused by an infection, the human papillomavirus (HPV).
The HPV is a common virus. There are more than 200 types of HPV, most of which are relatively harmless. Most HPV infections are typically cleared within one to two years by the body’s natural defences.
However, 15 – 20 types of HPV are oncogenic (cancer causing). HPV 16 and 18 account for an estimated 70 percent of all cervical cancers. This is followed by HPV 45 (two to eight percent), HPV 31 (two to seven percent), HPV 33 (three to five percent) and in smaller proportions by HPV types 52, 58, 35, 39, 51, 56. Therefore, virtually all cervical cancers are due to infection with an oncogenic HPV type.
HPV is also linked to several other cancers namely 70 percent of anal cancers, 50 percent of cancers of the vulva, vagina and penis and 20 percent of oropharyngeal cancers.
The vaccine contains proteins which resemble the virus but since they do not contain viral DNA, they cannot infect cells and reproduce. However, they are able to induce the formation of anti-HPV antibodies which confer protection against HPV infection. By preventing infection with HPV, the vaccine is preventing the initiation of cervical cancer and is effectively behaving as an anti-cancer vaccine. Studies with a follow-up period of five years, have shown that the vaccine was 100 percent protective against HPV 16- & 18-related cervical cancers.
Recent studies have also shown that the vaccine demonstrated cross-protection against the third and fourth commonest oncogenic types, HPV 31 and 45 which account for approximately 10 percent of all cervical cancers.
Since HPV infection is acquired within the first few years of sexual debut, the World Health Organisation recommends that the vaccine should be administered
before any risk of exposure to HPV. The primary target being girls aged nine to 13 years, the intention being to reach them prior to sexual debut. And the secondary target comprising of young women age of 14 – 26 years who visit their doctors for health checks and presents an opportunity to discuss HPV and the potential benefits of the vaccine.
Experience with many paediatric vaccines have demonstrated that they confer long term protection. Hepatitis B vaccine which is protective against chronic hepatitis and liver cancer, has been shown to be due to the persistence of a strong immunological memory. A similar memory response has been demonstrated with the cervical cancer vaccine upon challenge with an antigen five years later. The rationale for paediatric and adolescent vaccination is therefore based on good scientific evidence.