How does Cervarix work?
Dear Dr Mitchell,
I'm 37 years old and a single mom of a 12 year old girl. Can you please explain how the drug Cervarix works? I'm interested in taking it, but I know very little about it and I am afraid of getting cancer of any sort.
Cervarix is a vaccine that is used to prevent cervical cancer. Cervical cancer is caused by the human papillomavirus which is transmitted by sexual contact. Once you have even been sexually active you are at risk of being exposed to the Human Papillomavirus (HPV). HPV may be present in women and men with no obvious signs or symptoms. Sometimes it may present in the form of genital warts or it may be picked up by doing a pap smear in a routine physical examination.
Over 80 per cent of sexually active women will harbour HPV after one episode of sexual activity. Individuals with a good immune system will, however, clear their system of the virus within six to 18 months. When the infection persists, this leads to abnormal changes in the cells of the cervix, vulva, vagina, anus and throat and results in cancer in these sites. Men are also at risk and can get cancer of the penis though this is a lot less common than cervical cancer.
The four most common types of HPV that cause cancer of the cervix are types 16, 18, 3, and 45. Cervarix is designed to produce high and sustained levels of antibodies to subtypes 16 and 18, with significant coverage against types 31 and 45. These account for over 80 per cent of the cases of cervical cancer. When Cervarix is given, the level of antibodies in the tissues of the cervix, vulva, vagina, anus, and throat is higher, binding to the HPV and preventing the virus from penetrating into the deeper tissues and causing cancer. The human papillomavirus normally enters the tissues through small breaks in the skin and mucous membranes. These micro-abrasions occur at all times, especially during sexual intercourse or other sexual contact.
Cervarix is given in a three-dose schedule. The first vaccine is given, followed by the second one a month later, and the third one six months from the first one (0, 1, 6). All studies done show that the vaccine gives long-lasting protection for at least 20 years and beyond and there is currently no need for a booster vaccine. It is given to all women between the ages 10 to 55 years. Vaccination at an early age is ideal because the body responds best in the younger age group and produces high levels of the neutralising antibodies to HPV. However, the vaccine works well up to the age of 55 years. Men can also be vaccinated, thus reducing the burden of disease in women and at the same time reducing their risk of cancer of the penis, oropharynx and anus.
The vaccine can be given to women who have already had HPV infection. Once you had the infection, treatment is directed at the abnormal changes that the virus causes in the genital tract, and with the immune system will help clear the virus from the system. The vaccine will then prevent reinfection from repeated exposure to the HPV during sexual contact. The vaccine is, however, for prevention of HPV infection, not for treatment. The vaccine has been shown to be safe in all the age groups in both men and women.
Screening with pap smear should continue even in vaccinated women. This is important to detect abnormal changes that may occur due to the subtypes not covered by the Cervarix vaccine. Common usage does not prevent infection with HPV since the virus may be present in areas where the condom does not cover, such as vulva, scrotum and groin areas. As such, condom usage only gives a 75 per cent reduction in HPV infection and is not to be seen as an alternative to vaccination.
Vaccination with Cervarix and screening with the pap smear is the way forward to reduce cervical cancer in the future. You and your daughter should definitely be vaccinated.
Dr Sharmaine Mitchell is an obstetrician and gynaecologist. Send questions via e-mail to allwoman@ jamaicaobserver.com; write to All Woman, 40-42 1/2 Beechwood Ave, Kingston 5; or fax to 968-2025. Dr Mitchell cannot provide personal responses.
The contents of this article are for informational purposes only and must not be relied upon as an alternative to medical advice or treatment from your own doctor.