Human papillomavirus prevention
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Most people become infected with various cutaneous HPV types during childhood. Papillomaviruses have a sturdy outer protein shell or "capsid" that renders them capable of lingering in the environment for long periods of time. Avoiding contact with contaminated surfaces, such as the floors of communal showers or airport security lines, might reduce the risk of cutaneous HPV infection. Treating common warts soon after they first appear may also reduce the spread of the infection to additional sites.
Genital HPV infections may be distributed widely over genital skin and mucosal surfaces, and transmission can occur even when there are no overt symptoms. Several strategies should be employed to minimize the risk of developing diseases caused by genital HPVs:
Prevention
Vaccine
On June 8, 2006, the FDA approved Gardasil, a prophylactic HPV vaccine which is marketed by Merck. The vaccine trial,[1] conducted in adult women with a mean age of 23, showed protection against initial infection with HPV types 16 and 18, which together cause 70 percent of cervical cancers. HPV types 16 and 18 also cause anal cancer in men and women.
The trial also showed 100% efficacy against persistent infections, not just incident infections. The vaccine also protects against HPV types 6 and 11, which cause 90 percent of genital warts. Women aged nine through twenty-six can be vaccinated, though the trial did not test minors. GlaxoSmithKline is expected to seek approval for a prophylactic vaccine targeting HPV types 16 and 18 early in 2007, known as Cervarix. Since the current vaccine will not protect women against all the HPV types that cause cervical cancer, it will be important for women to continue to seek Pap smear testing, even after receiving the vaccine. In addition, the Centers for Disease Control and Prevention (CDC) recommends vaccinating women who have already been diagnosed with HPV.
The vaccine has no side effects with the exception of soreness around the injection area. The FDA and CDC consider the vaccine to be completely safe. It does not contain mercury, thimerosal or live virus (only dead virus).[2] Merck, the manufacturer of Gardasil, will continue to test women who have received the vaccine to determine the vaccine's efficacy over the period of a lifetime.
Both men and women are carriers of HPV. To eradicate the disease, men will eventually need to be vaccinated. Studies are being conducted now to determine the efficacy of vaccinating boys with the current vaccine.[3]
The vaccine (commonly known as Gardasil) is delivered in a series of three shots over six months at a cost of approximately $360 (US dollars). The CDC recommends that girls and women between the ages of 11 and 26 be vaccinated,[2] though girls as young as 9 may benefit.[4]
Condoms
Although condoms are highly effective for preventing the transmission of other sexually transmitted diseases (STDs), recent studies have concluded that condoms only offer partial protection, at best, against the transmission of genital HPVs.[5][6]
This may be due to the fact that HPVs can infect genital skin areas that are not covered by condoms. On the other hand, some studies have suggested that regular condom use can effectively limit the ongoing persistence and spread of HPV to additional genital sites in individuals who are already infected.[7][8]
Thus, condom use may reduce the risk that infected individuals will progress to cervical cancer or develop additional genital warts. A 2006 study of 82 college students suggests that condoms can be up to 70% effective for preventing genital HPV infection if used for every sexual encounter.[6] Planned Parenthood recommends condom use to reduce the risk of contracting HPV,[9] but the Centers for Disease Control and Prevention maintain that "While the effect of condoms in preventing HPV infection is unknown, condom use has been associated with a lower rate of cervical cancer, an HPV-associated disease."[10]
Microbicides
Ongoing research has suggested that several inexpensive chemicals might serve to block HPV transmission if applied to the genitals prior to sexual contact.[11] These candidate agents, known as topical microbicides, are currently undergoing clinical efficacy testing. A recent study indicates that some sexual lubricant brands that use a gelling agent called carrageenan can inhibit papillomavirus infection in vitro.[12] See Carrageenan#Sexual lubricant and microbicide for details.
Clinical trials are needed to determine whether carrageenan-based sexual lubricant gels are effective for blocking the sexual transmission of HPVs in vivo.
Nutrition
Vitamin A
In a clinic-based case-control study to assess serum micronutrients as risk factors for cervical dysplasia, subjects in the lowest serum retinol quartile were at increased risk of CIN I compared with women in the highest quartile.[13]
Vitamin C
Risk of type-specific, persistent HPV infection was lower among women reporting intake values of vitamin C in the upper quartile compared with those reporting intake in the lowest quartile.[14]
Vitamin E
HPV clearance time was significantly shorter among women with the highest compared with the lowest serum levels of tocopherols, but significant trends in these associations were limited to infections lasting </=120 days. Clearance of persistent HPV infection (lasting >120 days) was not significantly associated with circulating levels of tocopherols. Results from this investigation support an association of micronutrients with the rapid clearance of incident oncogenic HPV infection of the uterine cervix.[15]
A statistically significantly lower level of alpha-tocopherol was observed in the blood serum of HPV-positive patients with cervical intraepithelial neoplasia. The risk of dysplasia was four times higher for an alpha-tocopherol level < 7.95 mumol/l.[16]
Folic acid
Higher folate status was inversely associated with becoming HPV test-positive. Women with higher folate status were significantly less likely to be repeatedly HPV test-positive and more likely to become test-negative. Studies have shown that lower levels of antioxidants coexisting with low levels of folic acid increases the risk of CIN development. Improving folate status in subjects at risk of getting infected or already infected with high-risk HPV may have a beneficial impact in the prevention of cervical cancer.[17][18]
Carotenoids
Higher circulating levels of carotenoids were associated with a significant decrease in the clearance time of type-specific HPV infection, particularly during the early stages of infection (</=120 days). Clearance of persistent HPV infection (lasting >120 days) was not significantly associated with circulating levels of carotenoids.[15]
The likelihood of clearing an oncogenic HPV infection is significantly higher with increasing levels of lycopenes.[19] A 56% reduction in HPV persistence risk was observed in women with the highest plasma [lycopene] concentrations compared with women with the lowest plasma lycopene concentrations. These data suggests that vegetable consumption and circulating lycopene may be protective against HPV persistence.[20][21][22]
CoQ10
Women who had either CIN or cervical cancer had markedly lower levels of CoQ10 in their blood and in their cervical cells than the women who were healthy.
Fruits and Vegetables
Higher levels of vegetable consumption were associated with a 54% decrease risk of HPV persistence.[20] Consumption of papaya at least once a week was inversely associated with persistent HPV infection.[21]
Fish Oil
In a 1999 study, Docosahexaenoic acid inhibited growth of HPV16 immortalized cells.[23]
References
- ↑ Harper DM, Franco EL, Wheeler CM; et al. (2006). "Sustained efficacy up to 4.5 years of a bivalent L1 virus-like particle vaccine against human papillomavirus types 16 and 18: follow-up from a randomised control trial". Lancet. 367 (9518): 1247–55. doi:10.1016/S0140-6736(06)68439-0. PMID 16631880.
- ↑ 2.0 2.1
- ↑ "Cervical Cancer Vaccine Approved". WebMD. Retrieved 2007-08-17.
- ↑ "HPV and HPV Vaccine - HCP". 2006-08-01. Retrieved 2007-08-17.
- ↑ Holmes KK, Levine R, Weaver M (2004). "Effectiveness of condoms in preventing sexually transmitted infections". Bull. World Health Organ. 82 (6): 454–61. PMID 15356939.
- ↑ 6.0 6.1 Winer RL, Hughes JP, Feng Q; et al. (2006). "Condom use and the risk of genital human papillomavirus infection in young women". N. Engl. J. Med. 354 (25): 2645–54. doi:10.1056/NEJMoa053284. PMID 16790697.
- ↑ Moscicki AB (2005). "Impact of HPV infection in adolescent populations". The Journal of adolescent health : official publication of the Society for Adolescent Medicine. 37 (6 Suppl): S3–9. PMID 16310138.
- ↑ Bleeker MC, Berkhof J, Hogewoning CJ; et al. (2005). "HPV type concordance in sexual couples determines the effect of condoms on regression of flat penile lesions". Br. J. Cancer. 92 (8): 1388–92. doi:10.1038/sj.bjc.6602524. PMID 15812547.
- ↑ "Planned Parenthood - HPV". Retrieved 2007-08-17.
- ↑ "STD Facts - Human papillomavirus (HPV)". Retrieved 2007-08-17.
- ↑ Howett MK, Kuhl JP (2005). "Microbicides for prevention of transmission of sexually transmitted diseases". Curr. Pharm. Des. 11 (29): 3731–46. PMID 16305508.
- ↑ Buck CB, Thompson CD, Roberts JN, Müller M, Lowy DR, Schiller JT (2006). "Carrageenan is a potent inhibitor of papillomavirus infection". PLoS Pathog. 2 (7): e69. PMID 16839203.
- ↑ Yeo AS, Schiff MA, Montoya G, Masuk M, van Asselt-King L, Becker TM (2000). "Serum micronutrients and cervical dysplasia in Southwestern American Indian women". Nutrition and cancer. 38 (2): 141–50. PMID 11525590.
- ↑ Giuliano AR, Siegel EM, Roe DJ; et al. (2003). "Dietary intake and risk of persistent human papillomavirus (HPV) infection: the Ludwig-McGill HPV Natural History Study". J. Infect. Dis. 188 (10): 1508–16. PMID 14624376.
- ↑ 15.0 15.1 Goodman MT, Shvetsov YB, McDuffie K; et al. (2007). "Hawaii cohort study of serum micronutrient concentrations and clearance of incident oncogenic human papillomavirus infection of the cervix". Cancer Res. 67 (12): 5987–96. doi:10.1158/0008-5472.CAN-07-0313. PMID 17553901.
- ↑ Kwaśniewska A, Tukendorf A, Semczuk M (1997). "Content of alpha-tocopherol in blood serum of human Papillomavirus-infected women with cervical dysplasias". Nutrition and cancer. 28 (3): 248–51. PMID 9343832.
- ↑ Piyathilake CJ, Henao OL, Macaluso M; et al. (2004). "Folate is associated with the natural history of high-risk human papillomaviruses". Cancer Res. 64 (23): 8788–93. doi:10.1158/0008-5472.CAN-04-2402. PMID 15574793.
- ↑ Kwaśniewska A, Tukendorf A, Goździcka-Józefiak A, Semczuk-Sikora A, Korobowicz E (2002). "Content of folic acid and free homocysteine in blood serum of human papillomavirus-infected women with cervical dysplasia". Eur. J. Gynaecol. Oncol. 23 (4): 311–6. PMID 12214730.
- ↑ Sedjo RL, Papenfuss MR, Craft NE, Giuliano AR (2003). "Effect of plasma micronutrients on clearance of oncogenic human papillomavirus (HPV) infection (United States)". Cancer Causes Control. 14 (4): 319–26. PMID 12846362.
- ↑ 20.0 20.1 Sedjo RL, Roe DJ, Abrahamsen M; et al. (2002). "Vitamin A, carotenoids, and risk of persistent oncogenic human papillomavirus infection". Cancer Epidemiol. Biomarkers Prev. 11 (9): 876–84. PMID 12223432.
- ↑ 21.0 21.1 Giuliano AR, Siegel EM, Roe DJ; et al. (2003). "Dietary intake and risk of persistent human papillomavirus (HPV) infection: the Ludwig-McGill HPV Natural History Study". J. Infect. Dis. 188 (10): 1508–16. PMID 14624376.
- ↑ Giuliano AR, Papenfuss M, Nour M, Canfield LM, Schneider A, Hatch K (1997). "Antioxidant nutrients: associations with persistent human papillomavirus infection". Cancer Epidemiol. Biomarkers Prev. 6 (11): 917–23. PMID 9367065.
- ↑ Chen D, Auborn K (1999). "Fish oil constituent docosahexa-enoic acid selectively inhibits growth of human papillomavirus immortalized keratinocytes". Carcinogenesis. 20 (2): 249–54. PMID 10069461.