icon star paper   Articles  
Back grey_arrow_rt.gif
 
 
Risk of HIV infection attributable to oral sex among men who have sex with men and in the population of men who have sex with men
 
 
  We examined HIV infection and estimated the population-attributable risk percentage (PAR%) for HIV associated with fellatio among men who have sex with men (MSM). Among 239 MSM who practised exclusively fellatio in the past 6 months, 50% had three partners, 98% unprotected; and 28% had an HIV-positive partner; no HIV was detected. PAR%, based on the number of fellatio partners, ranges from 0.10% for one partner to 0.31% for three partners. The risk of HIV attributable to fellatio is extremely low.
 
Since HIV was identified as being sexually transmitted, there has been considerable interest in the risk associated with performing fellatio. Although early studies found no independent risk for fellatio, the high correlation among multiple sexual practices raised the possibility that risk existed but could not be detected. Subsequently, case reports accumulated, largely among men who denied other risk behaviors [1]. Researchers acknowledged that fellatio, although not an efficient route of infection, nonetheless appeared to carry a small risk. Two studies provided quantitative estimates of the low risk among men who have sex with men (MSM) [2, 3]. One [3] estimated the per-contact risk of unprotected fellatio with an HIV-positive or unknown HIV status partner [4/10 000; 95% confidence interval (CI) 0.01%, 0.17%] to be lower than the per-contact risk of acquiring HIV from protected receptive anal intercourse (RAI) (0.18%; 95% CI 0.10%, 0.28%).
 
Current 'safe sex' guidelines specify that unprotected orogenital sex is unsafe but low risk. A recent study of primary infection in San Francisco [4] reported that 8% of HIV-positive participants acquired HIV from fellatio. The abstract from the 2000 Retrovirus Conference, where this study was presented, reported that 6.6% (8/122 individuals) were classified as likely oral sex transmission. This finding has been widely interpreted that as many as 8% of HIV infections among MSM are attributable to fellatio [5]. It is understandable, given these conflicting messages, that individuals continue to ask for greater clarity regarding this risk. The population-attributable risk percentage (PAR%) is of special interest, because even a low-risk exposure could result in a substantial proportion of infections.
 
We present preliminary results from an ongoing study investigating orally acquired HIV infection demonstrating: (i) that such infection is rare; and (ii) conduct analyses using previously published data to show that the PAR% of HIV attributable to fellatio is also extremely low.
 
From December 1999 to 2001, individuals seeking HIV testing at an anonymous testing site in San Francisco were screened to identify those who in the past 6 months reported no anal or vaginal sex, had not injected drugs, and had performed fellatio on at least one male partner. Eligible participants completed a pre-HIV test survey, measuring a 6-month history of sexual practices. Post-interview HIV serology was conducted to determine participants' HIV serology using using enzyme immunoassays, Western blot confirmation, and a sensitive/less sensitive enzyme immunoassay strategy [6] to identify recently acquired infection. PAR% was estimated using Levin's formula: (p S(RR - 1)/(p(RR - 1) - 1) * 100), where p is the population exposure prevalence, and RR is relative risk [7]. An estimate of RR from previously published data was used [2], and the prevalence p of fellatio partners was obtained from data collected in a population-based study of MSM [8]. We estimated the prevalence p from data collected in baseline interviews in which participants were asked how many fellatio (receptive oral sex) partners they had had in the previous year. Analyses have shown that the prevalence of fellatio [9] and fellatio partners (unpublished data) has not changed significantly since that study was initiated. As the median number of reported fellatio partners in the previous year reported by participants in this study was three (range 0-400), we estimated the PAR% for one, two, and three fellatio partners.
 
Of 10 283 anonymous testing site clients, 413 (4%) were eligible, and 243 (2.3%) participated. Of those, 239 (98%) were men, whose median age was 39 years, and all were MSM. Four women were dropped from the analysis. No recently acquired HIV infections were detected and the estimated probability of orally acquired HIV was 0 (95% CI 0, 1.5%). The median number of fellatio partners in the past 6 months was three (interquartile range 1-6), almost all (98%) were unprotected. One third (35%) reported getting semen in their mouth, and of those, 70% swallowed it. Fellatio on a known HIV-positive partner was reported by 28%; of those, 81% did not use a condom, and 39% had swallowed ejaculate.
 
The PAR% rises as the number of partners increases: PAR% for one fellatio partner (p = 18%, RR = 1.01) was estimated at 0.18%, for two fellatio partners (p = 12%, RR = 1.02) at 0.25% and for three fellatio partners (p = 10%, RR = 1.03) as 0.31%. The cumulative PAR% for one to three fellatio partners could thus be 0.74%.
 
The absence of HIV infections detected in this sample confirms previous research that orally acquired HIV infection is rare. HIV prevalence and incidence among MSM who tested at the same anonymous testing sites in San Francisco during a similar time period (December 1999 to February 2001) were appreciably higher. The overall prevalence of HIV infection was 3.3% (95% CI 2.9-3.9), and among repeat testers the incidence was 1.9/100 person-years (95% CI 1.6-2.3). Among those who reported unprotected RAI, HIV prevalence and incidence were 5.1% (95% CI, 4.1-6.3) and 3.5/100 person-years (95% CI, 2.7-4.5), respectively. Among those who reported protected RAI, HIV prevalence and incidence was 2.3% (95% CI, 1.7-3.1) and 1.7/100 person-years (95%CI 1.2-2.3), respectively (T. Kellogg, San Francisco Department of Public Health, personal communication). These figures reveal the striking difference in the risk of HIV between those who report exclusively fellatio and those who report higher-risk sexual behaviors.
 
A strength of this study is that participants were queried about behaviors before HIV testing. Consistently, studies that rely on individuals identifying 'how they got infected', report a higher proportion of orally acquired infections than can be reliably established [4, 5]. HIV-positive MSM may inaccurately report higher-risk exposures for reasons including social desirability and recall. Men may also report having only oral sex as a risk behavior because that is the only 'unprotected' sexual behavior they engage in, not acknowledging anal sex when a condom was used. Vittinghoff et al.[3] hypothesized that condom breakage or slippage could account for the higher per-act infectivity of protected anal sex compared with unprotected fellatio.
 
Our results are based on a modest sample size; therefore, we cannot rule out the possibility that the probability of infection is indeed greater than zero. Our data and those of others (D. Osmond, San Francisco Young Men's Health Study: less than 3%, unpublished data) show that the proportion of individuals who engage exclusively in fellatio is very low, thus obtaining precise and reliable estimates of the per-partner and per-contact risks of acquiring HIV from fellatio will be difficult. The likely importance of heterogeneity of susceptibility and infectiousness add further uncertainty to quantifying risk.
 
Our calculations showing very low PAR% are consistent with the findings of extremely low individual risk. In addition, if one considers that only a fraction of those who report fellatio are actually exposed to semen (35%), the PAR% will be considerably lower.
 
These data confirm that the risk of HIV infection attributable to fellatio among MSM and in the MSM population is especially low. It is important that health professionals, including HIV counsellors have valid information to impart to their sexually active clients. If individuals believe that the risk of HIV from fellatio is high or on a par with well-documented high-risk exposures such as anogenital sex, they may not feel that sexual behavior choices make a difference. Acquiring HIV through fellatio is significantly less risky than from anal sex, and therefore one's choice of sexual practices do matter. AIDS 2002; 16(17):2350-2352; Kimberly Page-Shafer et al.
 
The study does not appear to report how many instances of fallatio individuals had.
 
Commentary from the CDC HIV/STD/TB Prevention News Update 12/02/02:
 
Since HIV was identified as being sexually transmitted, there has been considerable interest in the risk associated with performing fellatio. Although early studies found no independent risk for fellatio, the high correlation among multiple sexual practices raised the possibility that risk existed but could not be detected. Subsequently, case reports accumulated, largely among men who denied other risk behaviors. Researchers acknowledged that fellatio, although not an efficient route of infection, nonetheless appeared to carry a small risk.
 
Current safe sex guidelines specify that unprotected orogenital sex is unsafe but low risk. A recent study of primary infection in San Francisco reported that 8 percent of HIV-positive participants acquired HIV from fellatio. This finding has been widely interpreted that as many as 8 percent of HIV infections among MSM are attributable to fellatio. The population-attributable risk percentage (PAR%) is of special interest, because even a low-risk exposure could result in a substantial proportion of infections.
 
The authors present preliminary results from an ongoing study investigating orally acquired HIV infection demonstrating: that such infection is rare; and conduct analyses using previously published data to show that the PAR% of HIV attributable to fellatio is also extremely low.
 
From December 1999 to 2001, individuals seeking HIV testing at an anonymous testing site in San Francisco were screened to identify those who in the past 6 months reported no anal or vaginal sex, had not injected drugs, and had performed fellatio on at least one male partner. Eligible participants completed a pre-HIV test survey, measuring a 6-month history of sexual practices. Post-interview HIV serology was conducted to determine participants' HIV serology using enzyme immunoassays, Western blot confirmation, and a sensitive/less sensitive enzyme immunoassay strategy to identify recently acquired infection.
 
Of 10,283 anonymous testing site clients, 413 (4 percent) were eligible, and 243 (2.3 percent) participated. Of those, 239 (98 percent) were men, whose median age was 39 years, and all were MSM. Four women were dropped from the analysis.
 
No recently acquired HIV infections were detected and the estimated probability of orally acquired HIV was 0. The median number of fellatio partners in the past 6 months was three, almost all (98 percent) were unprotected. One-third (35 percent) reported getting semen in their mouth, and of those, 70 percent swallowed it. Fellatio on a known HIV-positive partner was reported by 28 percent; of those, 81 percent did not use a condom, and 39 percent had swallowed ejaculate.
 
The PAR% rises as the number of partners increases: PAR% for one fellatio partner was estimated at 0.18 percent, for two fellatio partners at 0.25 percent and for three fellatio partners as 0.31 percent. The cumulative PAR% for one to three fellatio partners could thus be 0.74 percent.
 
The authors' results are based on a modest sample size; therefore, they cannot rule out the possibility that the probability of infection is indeed greater than zero. The calculations showing very low PAR% are consistent with the findings of extremely low individual risk. In addition, if one considers that only a fraction of those who report fellatio are actually exposed to semen (35 percent), the PAR% will be considerably lower.
 
"These data confirm that the risk of HIV infection attributable to fellatio among MSM and in the MSM population is especially low," the authors concluded. "It is important that health professionals, including HIV counselors have valid information to impart to their sexually active clients. If individuals believe that the risk of HIV from fellatio is high or on a par with well-documented high-risk exposures such as anogenital sex, they may not feel that sexual behavior choices make a difference. Acquiring HIV through fellatio is significantly less risky than from anal sex, and therefore one's choice of sexual practices do matter."
 
CDC Fact Sheet (Dec 2000) says:
 
What You Should Know about Oral Sex: Oral Sex Is Not Considered Safe Sex
 
Like all sexual activity, oral sex carries some risk, particularly when one partner or the other is known to be infected with HIV, when either partneršs HIV status is not known, and/or when one or the other partner is not monogamous or injects drugs. Numerous studies have demonstrated that oral sex can result in the transmission of HIV and other sexually transmitted diseases (STDs). Abstaining from oral, anal, and vaginal sex all together or having sex only with a mutually monogamous, uninfected partner are the only ways that individuals can be completely protected from the sexual transmission of HIV.
 
Oral Sex is a Common Practice
 
Oral sex involves giving or receiving oral stimulation (i.e. sucking or licking) to the penis, the vagina, and/or the anus. Fellatio is the technical term used to describe oral contact with the penis. Cunnilingus is the technical term which describes oral-vaginal sex. Anilingus (sometimes called "rimming") refers to oral-anal contact. Studies indicate that oral sex is commonly practiced by sexually active male-female and same-gender couples of various ages, including adolescents. Although there are only limited national data about how often adolescents engage in oral sex, some data suggest that many adolescents who engage in oral sex do not consider it to be sex; therefore they may use oral sex as an option to experience sex while still, in their minds, remaining abstinent. Moreover, many consider oral sex to be a safe or no risk sexual practice. In a recent national survey of teens conducted for The Kaiser Family Foundation, 26% of sexually active 15 to 17 year olds surveyedresponded that one "cannot become infected with HIV by having unprotected oral sex", and an additional 15% didnšt know whether or not one could become infected in that manner.
 
Oral Sex and the Risk of HIV Transmission
 
The risk of HIV transmission from an infected partner through oral sex is much smaller than the risk of HIV transmission from anal or vaginal sex. Because of this, measuring the exact risk of HIV transmission as a result of oral sex is very difficult. In addition, since most sexually active individuals practice oral sex in addition to other forms of sex, such as vaginal and/or anal sex, when transmission occurs, it is difficult to determine whether or not it occurred as a result of oral sex or other more risky sexual activities. Finally, several co-factors can increase the risk of HIV transmission through oral sex, including: oral ulcers, bleeding gums, genital sores, and the presence of other STDs.
 
Documented Case of Fellatio:
 
Although the risk is many times smaller than anal or vaginal sex, HIV has been transmitted to receptive partners through fellatio, even in cases when insertive partners didn't ejaculate ("cum").
 
Documented Case of Cunnilingus:
 
The risk of HIV transmission during cunnilingus is extremely low compared to vaginal and anal sex. However, there have been a few cases of HIV transmission most likely resulting from oral-vaginal sex.
 
Documented Case of Oral-Anal Sex: There has been one published case of HIV transmission associated with oral-anal sexual contact.
 
Other STDs Can Also Be Transmitted From Oral Sex
 
Scientists have documented a number of other sexually transmitted diseases that have also been transmitted through oral sex. Herpes, syphilis, gonorrhea, genital warts (HPV), intestinal parasites (amebiasis), and hepatitis A are examples of STDs which can be transmitted during oral sex with an infected partner.
 
Reducing the Risk of HIV Transmission Through Oral Sex
 
The consequences of HIV infection are life-long, life-threatening, and extremely serious. You can lower any already low risk of getting HIV from oral sex by using latex condoms each and every time. For cunnilingus or anilingus, plastic food wrap, a condom cut open, or a dental dam can serve as a physical barrier to prevent transmission of HIV and many other STDs. Because anal and vaginal sex are much riskier and because most individuals who engage in unprotected (i.e. without a condom) oral sex also engage in unprotected anal and/or vaginal sex, the exact proportion of HIV infections attributable to oral sex alone is unknown, but is likely to be very small. This has led some people to believe that oral sex is completely safe. It is not.
 
References
 
1.Rothenberg RB, Scarlett M, del Rio C, Reznik D, O'Daniels C. Oral transmission of HIV. AIDS 1998, 12:2095-2105.
 
2.Page-Shafer K, Veugelers PJ, Moss AR, Strathdee S, Kaldor JM, van Griensven GJ. Sexual risk behavior and risk factors for HIV-1 seroconversion in homosexual men participating in the Tricontinental Seroconverter Study, 1982-1994 [published erratum appears in Am J Epidemiol 1997 15 Dec; 146(12):1076]. Am J Epidemiol 1997, 146:531-542.
 
3.Vittinghoff E, Douglas J, Judson F, McKirnan D, MacQueen K, Buchbinder SP. Per-contact risk of human immunodeficiency virus transmission between male sexual partners. Am J Epidemiol 1999, 150:306-311.
 
4.Dillon B, Hecht F, Swanson M, et al. Primary HIV infections associated with oral transmission. In: 7th Conference on Retroviruses and Opportunistic Infections. San Francisco, 2000 [Abstract 473].
 
5.Hawkins D. Oral sex and HIV transmission. Sex Transm Infect 2001, 77:307-308.
 
6.Janssen RS, Satten GA, Stramer SL, et al. New testing strategy to detect early HIV-1 infection for use in incidence estimates and for clinical and prevention purposes [published erratum appears in JAMA 1999 26 May; 281(20):1893]. JAMA 1998, 280:42-48.
 
7.Kelsey JL, Thompson WD, Evans AS. Methods in observational epidemiology. New York, NY: Oxford University Press, Inc.; 1986.
 
8.Osmond DH, Page K, Wiley J.et al. HIV infection in homosexual and bisexual men 18 to 29 years of age: the San Francisco Young Men's Health Study. Am J Public Health 1994, 84:1933-1937.
 
9.Osmond DH, Buchbinder S, Cheng A.et al. Prevalence of Kaposi sarcoma-associated herpesvirus infection in homosexual men at beginning of and during the HIV epidemic. JAMA 2002, 287:221-225.
 
 
 
  icon paper stack View Older Articles   Back to Top   www.natap.org