Sunday, August 10, 2008

HPV infection is a major cause of cervical cancer

Hope in HPV vaccine

As HPV infection is a major cause of cervical cancer, vaccination offers the hope of a reduction in the incidence of this cancer.

Human papilloma virus (HPV) is a common sexually transmitted infection.

The HPV virus needs to infect cells in order to survive. Once inside a cell, it directs the cell to make copies of it and to infect other healthy cells. The infected cells eventually die and are shed from the body. When the virus is shed, it can infect another person.

There are different types of HPV. The low risk types, such as HPV6 and HPV11 cause benign genital and respiratory warts, while persistent infection with high-risk types such as HPV16 and HPV18 is associated with increased risk of high grade cervical intraepithelial neoplasia (CIN), which is a precursor of cervical cancer.

The genital warts (condylomas) may appear on the outside or inside the reproductive tract. It can spread to nearby skin or to a sexual partner.

Genital warts are more likely to occur in people who have more than one sexual partner or whose sexual partner has more than one partner. Other reproductive tract infections are often associated with genital warts.

HPV is a major cause of cancer of the cervix. HPV infections by the high risk types are common in young sexually active women. Most clear spontaneously without ever causing cervical intraepithelial neoplasia while some develop a persistent infection.

Hence, cervical cancer can be considered a rare consequence of persistent infection with one or more high risk types, with other as yet undefined factors playing a role.

Studies suggest that HPV may also cause cancer of the vulva, vagina, anus, some cancers of the ompharynx (middle part of the throat that includes the base of the tongue and tonsils).

The more sexual partners a person has, the more likely he or she will get HPV infection. The vast majority of HPV infections go away without treatment. Certain factors like smoking, multiple sexual partners, having many children, oral contraceptive use and HIV infection are associated with an increase in the risk of developing cervical cancer.

As HPV may have no symptoms, it may be more common than is thought.

Most genital warts may appear within a few weeks or months after sexual contact with an infected person or they may not appear at all

The warts are fiat, abnormal growths in the genital area including the cervix. Sometimes, the warts are extensive with a cauliflower-like appearance.

There is no published data on the disease burden of HPV infection in our country as HPV is not a notifiable infection.

However, cervical cancer is the second most common cancer in women here.

The National Cancer Register for 2003 shows the incidence in Peninsular Malaysia as 13.4 and 62.9 per 100,000 women in the age groups 15 to 49 and 50 to 69 years respectively.

HPV vaccines
Women who had previously been infected by a particular HPV type are unlikely to get re-infected by the same HPV type because of the antibodies produced.

There are two types of HPV vaccines: a bivalent (HPV16 and HPV18) and a quadriva]ent vaccine (HPV 6, 11, 16 and 18).

Both vaccines provide protection against 70% of the HPV types that cause cervical cancer.

In addition, the quadrivalent vaccine provides protection against 90% of the HPV types that cause genital warts.

The vaccines do not provide protection against HPV types that a person has been exposed to.

However, a person who has had HPV may still benefit from the vaccine because most people are not infected with all the types of HPV contained in the vaccine.

The vaccines do not provide protection against other sexually transmitted infections (STI).

Information about some aspects of HPV vaccines is yet to be clarified. This includes the duration of protection although current data indicates that the protection after vaccination lasts at least five years.

The vaccines are given by injection in the upper arm. The second and third doses are given two and six months later.

The optimal age for HPV vaccination is between the age of nine and 26 years.

Effectiveness and safety
The HPV vaccines are effective. Studies of both vaccines, to-date, have reported near 100% efficacy.

HPV vaccines are generally well tolerated and reactions are minimal. It is usually limited to some pain, swelling, itching and redness at the injection site, fever, nausea, vomiting, dizziness and fainting.

Other side effects reported include swollen glands in the neck, armpit, or groin, headache, skin rashes, joint pain, aching muscles, unusual tiredness or weakness, and a general feeling of being unwell.

Allergic reactions have been reported. They include difficulty in breathing, wheezing and rashes. Some of these reactions are severe.

It is important to inform your doctor if you or your child has had an allergic reaction to the vaccine; has a bleeding disorder; is immunocompromised, such as with HPV infection; is pregnant or is planning to get pregnant, as the vaccine is not recommended for use in pregnant women; has a fever more than 37.8C; and is taking or intends to take any medicines including over the counter medicines.

HPV vaccination is no substitute for Pap smear screening. Those who have received HPV vaccines should continue Pap smear screening.

An abnormal Pap smear does not mean that a person has HPV infection or any other condition, including cancer.

It does mean that you have to be examined with a procedure called colposcopy. This involves using a magnifying instrument to look at the cervix, vagina, vulva and anus.

If there are areas that appear suspicious, a biopsy, in which a small sample of tissue is removed for microscopic examination, will be performed.

As HPV infection is a major cause of cervical cancer, vaccination offers the hope of a reduction in the incidence of cervical cancer.

However, other measures are needed to eradicate cervical cancer. They include widespread Pap smear screening and safe sexual practices.

One should also remember that HPV vaccines prevent HPV infections. It cannot be extrapolated to the prevention of cervical cancer as there are, apart from HPV infection, other as yet undefined factors playing a role in the genesis of cervical cancer.


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