Pictured Valdiserri ( left ) and Leone. Photos by Bob Roehr
The Centers for Disease Control and Prevention ( CDC ) issued its first preventive treatment guidelines for those accidentally exposed to HIV in a nonoccupational setting. Guidelines for healthcare workers exposed to possible infection, through needle sticks or blood exposure, have been in place since 1996.
Nonoccupational postexposure prophylaxis ( nPEP ) should not be seen as a substitute for safer sex and other practices that avoid such exposure entirely, Ronald O. Valdiserri stressed during a Jan. 20 conference call with reporters. He is the deputy director of the CDC's National Center for HIV, STD and TB Prevention.
Nor should it be thought of as 'a morning after pill.' Valdiserri explained that the 28-day nPEP regimen requires rigorous compliance, often carries unpleasant side effects, and is believed to be only about 80% effective in preventing HIV infection. Rather, nPEP should be thought of as 'a safety net.'
The nPEP guidelines require patients to seek treatment within 72 hours of possible exposure to HIV. Studies in animals and healthcare workers exposed on the job suggest that early treatment is most effective and that after 72 hours there is decreasing value in treating to prevent infection.
'People who would benefit from nPEP include those who occasionally lapse at safer sex [ with a person known to be HIV positive ] or drug use behavior, or are exposed through sexual assault or an accident,' said the CDC's Lisa Grohskopf.
'If the HIV status of the source person is not known, the guidelines recommend that uses of nPEP be considered on a case by case basis.' Ideally the source partner will take a rapid HIV test to learn their serostatus.
'This is not recommended for people whose behavior results in frequent recurrent exposures to HIV. This includes people who have HIV infected sex partners and rarely use condoms, and injection drug users who often share equipment,' she said.
Any of the regimens used to treat HIV may be used in an nPEP setting. However, nevirapine should be avoided because long-term use poses risk of liver damage that other drugs do not. Efavirenz may increase the risk of birth defects and so should be avoided by women who are pregnant or of childbearing age.
The regimen costs between $600 and $1,000 depending on the combination of drugs selected. Public and private health insurance plans are likely to vary in wither or not they cover the cost of nPEP.
Valdiserri said, 'No single prevention strategy can completely eliminate the risk of HIV infection for all at risk populations. Biomedical interventions must be used in combination with other proven prevention strategies … [ such as ] abstinence, mutual monogamy with an uninfected partner, consistent and correct condom use, and the use of sterile needles and syringes to inject drugs.'
Many have criticized the CDC for not issuing nPEP guidelines earlier and have raised the question of what prompted the agency to do so now. 'The field continues to evolve,' Valdiserri said in response, 'Rather than a single study, it was the preponderance of evidence' that led CDC to issue the nPEP guidelines at this time.
NPEP guidelines are common in Europe. California, Massachusetts, New York, and Rhode Island, and some local health departments have had similar guidelines in place for years. Those jurisdictions contain about half of the nation's HIV caseload and thus much of the risk of exposure to the virus.
Data on how widely nPEP has been used is sketchy because that use does not have to be reported to the CDC. Grohskopf said that makes it difficult to determine what if any impact these guideline changes will have.
One fear has been that the availability of nPEP might lead to increased risky behavior. But studies from pilot projects in San Francisco and elsewhere have given the cover that CDC had sought. Valdiserri said, 'There is no evidence that high risk behaviors have increased as a result of its availability.'
A potential risk in the guidelines is that physicians who are not greatly experienced with HIV may use a negative rapid antibody test as a reason to deny nPEP to a person at risk.
There is a period of acute HIV infection that runs from a few days after exposure to when antibodies appear in the blood, about 30 days later. During this period HIV viral load can be extremely high but not show up on the standard test, which measures the antibody and not the virus itself. A general practitioner may not be aware of this.
Grohskopf said that such decisions should be made on a case by case basis. 'It is important to know as much as can possibly be known about the source person regarding any symptoms they may have had recently.'
Peter Leone runs the HIV/STD testing program in the state of North Carolina and has pioneered identification of early infection. He said their program has only rarely identified examples of transmission to another person during acute infection. 'I'm not sure why.'
He echoed Grohskopf's concern for the need to get as detailed a case history of the potentially infectious partner as possible. Having recently had sex with someone known to be HIV positive would be reason for concern and would strengthen the case for initiating nPEP.
Kenneth Mayer, medical research director at Fenway Community Health in Boston, supports the new guidelines. He said it is important that physicians have a starter pack of 3-4 days of an anti-HIV regimen available so that the patient can begin therapy immediately, while details of prescriptions and payments are worked out.