Does Interferon Treatment for Genital Warts Work?

Interferon drug in crystal form in a vial
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Genital warts are caused by human papillomavirus, or HPV. Unlike cervical cancer and other HPV-associated cancers, genital warts are caused by low risk strains of the virus. Like other types of HPV, these low-risk strains are highly contagious. Genital warts are easily spread by skin to skin contact.

Most genital warts treatments are topical. In other words, they treat the warts directly. The most common types of treatments for genital warts include:

  • Imiquimod cream - Individuals put this cream on their warts. It stimulates the immune system to fight the infection that causes warts. It is generally applied at bedtime.
  • Podofilox solution or gel - Individuals apply this drug directly to the warts, twice a day for three days. This is then followed by four days of no therapy. This treatment attacks the warts directly, rather than enhancing the immune system, like imiquimod. Podofilox can only be used on small areas of warts, and it should not be used during pregnancy.
  • Sinecatechins ointment - Individuals apply this ointment, made from green tea, three times daily. It is not known whether this treatment is safe during pregnancy. In addition, people should not have sex while the ointment is on their skin.
  • Cryotherapy uses liquid nitrogen to freeze off warts. It must be performed by a trained healthcare provider. It may take multiple treatments to remove warts entirely.
  • Electrocautery is another wart removal treatment performed by a healthcare provider. It is a way of burning off warts using electricity. As with cryotherapy, it may sometimes need to be repeated several times.

Warts can also be removed by a doctor using a scissors, scalpel, or carbon dioxide laser. Individuals should not try to remove their warts this way at home. 

Trying to remove your own warts can spread the infection or cause other health problems.

What all of the above treatments have in common is that they attack visible warts at the site of the warts. However, some people are uncomfortable having to touch their own warts to treat them. They may also be embarrassed to have a provider remove them. In such cases, a systemic treatment can seem quite tempting. A systemic treatment for genital warts is one that people could take as a pill or a shot. Contact with, or showing, the warts wouldn't be necessary for treatment. Interferon treatment for genital warts is one systemic treatment that some providers recommend. But does it work?

Interferon Treatment for Genital Warts

Interferons are molecules known as cytokines. Their role in the body is, essentially, to pass messages. In particular, their messages are known to be able to change the function of the immune system in response to certain types of viral infections.

In the lab, interferon treatment has been shown to be an effective way to address HPV infection. It works directly as an antiviral. It also tells infected cells to stop growing and causes an increased immune response. However, that success has been more difficult to replicate outside the lab.

Interferon treatment can either be local or systemic. Local treatment involves injecting interferon directly into warts or applying it to them. Systemic treatment involves injecting the drug under the skin or in the muscle to treat the whole body. There have been a number of experimental studies looking at whether interferon treatment helps heal genital warts. The results have been mixed. There have been some positive studies where interferon has been directly injected into warts or applied to them.

Local treatment seems to do an okay job of both clearing up warts and reducing the likelihood they'll come back.

However, using interferon treatment systematically has not been shown to be better than a placebo. In other words, getting an injection of interferon wasn't any better at treating warts than getting an injection of water.

Not all studies looking at systematic interferon treatment have used the drug alone. Some scientists have hoped that interferon injections might be useful after warts were removed using another treatment. As warts can return after being removed, it would be useful if interferon was an effective way to keep them from coming back. Unfortunately, out of a dozen trials that have looked at using interferon after wart removal, only one saw a significant improvement. Otherwise, treatment with interferon didn't make a big difference in either helping clear up warts after another treatment or keeping them gone.

Does Interferon Treatment for Genital Warts Work?

In summary, systemic treatment of genital warts with interferon does not seem to be effective. It is unlikely to help individuals get rid of warts or keep them from returning. Although there is some data suggesting that topical interferon treatment can be helpful, it is not clearly better than the established regimens. Therefore, it is not recommended as a form of genital wart treatment by the CDC.

Genital Warts - An Ounce of Prevention

Interferon as a systemic treatment for genital warts doesn't seem promising. However, there is a systemic form of prevention. Both Gardasil and Gardasil 9 are HPV vaccines that help keep individuals from becoming infected with the types of HPV most commonly associated with genital warts. They are quite effective, although not completely effective, when given before young people become sexually active. Countries such as Australia and Denmark, which have national HPV vaccination programs, have seen enormous declines in the number of individuals being diagnosed with genital warts. Currently, the United States recommends two doses of the HPV vaccine, 6-12 months apart, when young people are 11 or 12 years old. If a teenager has missed being vaccinated, young men can still be vaccinated through age 21 and young women through age 26. Transgender young adults, young men who have sex with men, and immunocompromised youth can also be vaccinated through age 26.

Sources:

Bollerup S, Baldur-Felskov B, Blomberg M, Baandrup L, Dehlendorff C, Kjaer SK. Significant Reduction in the Incidence of Genital Warts in Young Men 5 Years into the Danish Human Papillomavirus Vaccination Program for Girls and Women. Sex Transm Dis. 2016 Apr;43(4):238-42. doi: 10.1097/OLQ.0000000000000418.

Smith MA, Liu B, McIntyre P, Menzies R, Dey A, Canfell K. Trends in genital warts by socioeconomic status after the introduction of the national HPV vaccination program in Australia: analysis of national hospital data. BMC Infect  Dis. 2016 Feb 1;16:52. doi: 10.1186/s12879-016-1347-z.

Westfechtel L, Werner RN, Dressler C, Gaskins M, Nast A. Adjuvant treatment of anogenital warts with systemic interferon: a systematic review and meta-analysis. Sex Transm Infect. 2017 Aug 17. pii: sextrans-2017-053150. doi: 10.1136/sextrans-2017-053150.

Workowski KA, Bolan GA; Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines, 2015. MMWR Recomm Rep. 2015 Jun 5;64(RR-03):1-137. Erratum in: MMWR Recomm Rep. 2015 Aug 28;64(33):924.

Yang J, Pu YG, Zeng ZM, Yu ZJ, Huang N, Deng QW. Interferon for the treatment  of genital warts: a systematic review. BMC Infect Dis. 2009 Sep 21;9:156. doi: 10.1186/1471-2334-9-156.

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