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Why…

HPV – Human Papilloma Virus is a group of viruses that infects skin and mucosa (lining of throat, mouth and genital area). There are several strains or types, some of which are harmless with some others causing disease. The strains 6 and 11 are known to cause genital warts while 16 and 18 have been linked to cancer of the cervix (the neck of the womb). Some strains cause warts on the skin (verrucae). 70% of cervical cancers have been linked to strains 16 and 18. These strains of HPV are sexually transmitted – both men and women can be affected.

Risk factors for HPV infection include early age of sexual intercourse, multiple partners or a partner who has had multiple partners, weakened immune system (e.g. HIV infection) and smoking. Condoms are not adequate protection as genital warts can occur anywhere in the anogenital area, however their use is still advised as they offer protection against other sexually transmitted infections e.g. HIV, chlamydia.

HPV infection is cleared by our natural immunity in 90% of cases. Unfortunately natural immunity does not persist at adequate levels for too long after infection so reinfection is possible. In cases where natural immunity has not managed to ward off the infection, HPV 16 and 18 can cause gradual changes of the cervix which may initially become precancerous ( CIN 1,2 or 3 – cervical intraepithelial neoplasia) which runs a risk of turning into cancer over a period of 10 – 20 years if left untreated. (It is not essential that HPV will cause cancer of the cervix in every infected person but the risk is higher with the infection). HPV strains 6 and 11 cause 90% of genital warts but not cervical cancer. In men, these HPV strains can rarely cause anogenital cancers in addition to warts.

Types of vaccine available…

There are 2 cervical cancer vaccines available – Cervarix offering protection against strains 16 and 18 ie to cervical cancer and Gardasil protecting against strains 6, 11, 16 and 18 (genital warts and cervical cancer). These do not contain the virus and cannot give you the infection. Studies have shown protection for at least 8 years with some differences between the 2 vaccines. There is follow up of vaccinated people and 2 on-going studies in the Nordic countries and Costa Rica which will provide us more information on the need for a booster after this period in vaccinated individuals.

When…

Vaccines are licensed between 9 and 26 years of age and ideally before initiation of sexual activity as they work best in this situation. However they can be administered after this age after discussion with a doctor. Dosage schedule is 0, 1 and 6 months for Cervarix and 0, 2 and 6 months for Gardasil. The vaccine is generally safe with potential side effects being local redness, swelling or itching at the injection site. Headache and muscle aches can occur. Raised temperature, vomiting, dizziness are less common. Hives (urticarial) is rare. It should not be used if you have a yeast allergy. Vaccination is not advised in pregnancy. However, Gardasil is safe in lactation (avoid Cervarix). The UK, American and Australian vaccination schedule includes the HPV vaccine at 12- 13 years for girls. It is now licensed for boys of the same age to prevent genital warts and cancers.

Are pap smears still needed…

Yes, these are still recommended every 2-3 years as some cancer causing strains are not covered by the vaccine. Also the vaccine can take some years to provide protection against cervical cancer.

In summary…

Cervical cancer is the third most common cancer in women worldwide. The HPV vaccines have been shown to be 99 % effective in preventing cervical cancer caused by strains 16 and 18 and has a similar efficacy in preventing genital warts. Clinical studies have shown it to be safe thus far and the vaccine is recommended in the age group mentioned above. However we are still waiting to know from on-going trials whether this protection will last longer than 8 years and if a booster is needed in future.

Dr Charu Narayanan

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