Numerical benefits low for non-occupational PEP
Numerical benefits low for non-occupational PEP
Therapy proves costly per life saved
Post-exposure prophylaxis for HIV exposure outside the work setting has raised much interest lately. Yet, an analysis of who would benefit from such treatment shows the numbers would be relatively low, while the costs would be high.
The group considered at highest risk for HIV transmission men who have sex with other men has a transmission rate of .8 to 3.2% per contact of receptive anal sex, which is roughly equivalent to the risk of health care workers exposed to the virus through needlesticks, reported Susan Buchbinder, MD, chief of the research branch of the San Francisco AIDS Office, during a Centers for Disease Control and Prevention conference on post-exposure prophylaxis for non-occupational exposures. Yet only one-third to one-half of HIV seroconverters among gay men in the CDC’s "Jumpstart" study report having known their partner was infected, she noted. Moreover, none of the seroconverters in the unpublished study, which involved more than 2,000 men followed between 1993 and 1995, had a single, monogamous partner during the study period, she added.
Where do we draw the line?
In presenting data from the Jumpstart study and from an analysis of seroconverters in a retrospective HIVNET study, Buchbinder found that only 20% of all seroconverters in this population reported a single exposure. And because the majority of seroconverters didn’t suspect their partner was HIV-positive until after they became infected, many persons would be treated unnecessarily, she added.
The potential benefits of PEP are even lower for heterosexual couples. With the risk of HIV transmission from a single act of unprotected vaginal sex estimated for the female at .06% and lower for the male, PEP in this setting may not prove beneficial, said Nancy Padian, MD, an obstetrician at San Francisco General Hospital. At the same time, however, the risk increases with other factors, such as infection with other sexually transmitted diseases, heterosexual anal sex, and history of injection drug use.
"We know the risk is low, but there is a tremendous amount of heterogeneity that makes it difficult to give an individual person advice," she said.
One exposure where PEP already has been used is with nonconsensual sex, particularly in sexual assault cases where the assailant is known to be HIV-positive or at high risk for HIV. Data are lacking on the rate of HIV transmission among rape victims, but at least one study has shown that as many as 75% of sexually assaulted women experience genital injury, making them more prone to infection, Padian added.
The CDC has identified 26 cases of HIV resulting from child sexual abuse, but only seven cases were prosecuted, CDC officials noted. Another barrier to treating this group is that assault reports often come weeks or months after the incident.
The difficulty a clinician would have in advising someone whether to undergo PEP was illustrated by an anecdote from Mitch Katz, MD, an AIDS researcher and clinician at the San Francisco Department of Public Health. When a clinician asked Katz for advice on a patient considering PEP, the clinician lacked pertinent information that would help in making a decision, such as the type of sexual exposure, whether the partner used a condom, and what the partner’s risk factors were. Without detailed information it will be hard to make the kind of on-the-spot decision that is required for effective PEP, he added.
Some IDUs may be eligible
PEP also has been considered for injection drug users (IDUs), who make up more than one-third of the new cases of HIV. While IDUs typically inject several times a day, there are situations of single exposure where PEP could be justified, said Steve Jones, MD, a CDC epidemiologist. One qualifying subgroup is former users who experience a relapse and may have used dirty needles or injection equipment. Another group would be first-time users who have injected a single time under peer pressure.
Some of the barriers to PEP in IDUs is that drug treatment centers and correctional facilities are reluctant to provide that kind of treatment. IDUs themselves would be reluctant to report an exposure for fear of prosecution, he added.
Another at-risk group considered for PEP is infants who have been exposed to HIV through breast-feeding. This group is relatively small, however, with only about 90 cases of HIV reported from breast-feeding, CDC officials reported.
PEP becomes less attractive from a public health perspective when its cost-effectiveness is considered, said David Holtgrave, PhD, director for the CDC’s division of HIV/AIDS prevention intervention, resource, and support. A four-week course of PEP will cost $600 to $1,000, which in most cases will not be covered by insurance. By using data reported in an article on PEP recently published in the New England Journal of Medicine1, Holtgrave showed that PEP would be cost-effective only under limited and specific situations because so many people would be treated unnecessarily. By calculating the risk of transmission and a lifetime treatment cost for HIV of $195,000, he estimates that PEP would cost $33,900 per life-year saved for receptive anal intercourse, $133,278 for injection drug use, and $992,034 for receptive vaginal sex.
While $33,900 is not out of line for other preventive health measures, the cost for injection drug use and heterosexual sex becomes prohibitive compared to other measures society is willing to pay for, he noted. The cost must be weighed against the other HIV prevention measures that could be purchased for that price, he added.
One aspect of PEP not considered is the possibility that even if PEP failed, it could reduce viral load and slow the course of progression in a person who becomes infected, CDC officials pointed out. Another side benefit of PEP is the opportunity it provides clinicians for providing prevention education.
"One of the issues is, what do we offer those people who come forward," Katz point out. "It may not be antiretroviral drugs in every case, but nor should it be, I’m sorry there is nothing available, you don’t qualify, you are not the right exposure or weren’t fast enough getting here.’ We should not forget other useful things we can provide them screening for STDs, how to use condoms, how to get clean needles."
Reference
1. Katz M, Gerberding J. Post-exposure treatment of people exposed to the HIV virus through sexual contact or injection-drug use. N Engl J Med 1997; 336:1097-1100.
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