|Year : 2007 | Volume
| Issue : 2 | Page : 61-68
Post-exposure prophylaxis for HIV
Archana Sharma, YS Marfatia, Ragini Ghiya
Department of Skin and VD, Medical College and SSG Hospital, Vadodara, India
Y S Marfatia
Department of Skin and VD, Medical College and SSG Hospital, Vadodara
| Abstract|| |
Post-exposure prophylaxis (PEP) is a medical response given to prevent the transmission of pathogens after potential exposure. The PEP for HIV refers to a set of comprehensive services to prevent HIV infection in exposed individuals where the exposure can be occupational or non-occupational (nPEP) and the provision of short-term (28 days) antiretroviral drugs depending on risk assessment with follow-up. High concentration of free infectious virus and virus-infected cells have been reported in blood, genital fluids and cerebrospinal fluid. The average risk of HIV infection after percutaneous exposure to HIV-infected blood is 0.3%. The nPEP can be offered for cases like unprotected sexual exposure, sexual assault survivors, injecting drug users (IDUs) sharing equipment, etc. While considering PEP, evaluation of exposure, exposure source and exposed person is to be done and 2 or 3 drug PEP (depending upon the type of exposure) can be started within 72 h and need to be continued for 28 days. Drugs preferred are zidovudine + lamivudine. If needed, a boosted protease inhibitor can be added.
Keywords: Antiretroviral drugs, non-occupational (nPEP), post-exposure prophylaxis risk assessment
|How to cite this article:|
Sharma A, Marfatia Y S, Ghiya R. Post-exposure prophylaxis for HIV. Indian J Sex Transm Dis 2007;28:61-8
Post-exposure prophylaxis (PEP) is a medical response given to prevent the transmission of pathogens after potential exposure. The PEP for HIV refers to a set of comprehensive services to prevent HIV infection in exposed individuals where the exposure can be occupational or non-occupational (nPEP). These services include first aid care, counselling and risk assessment, HIV testing and depending on risk assessment, the provision of short-term (28 days) antiretroviral (ARV) drugs, with follow-up. Over 300 definite cases or possible health care worker HIV transmissions have been documented, 90% of which have occurred in either Europe or North America regions that collectively account for just 4% of the global burden of HIV infection.  It is likely, therefore, that the figure is an underestimate of the true number of HCW infections worldwide. Rey et al. reported that out of 27 European countries, 20 have produced national guidelines for occupational PEP while only 5 have guidelines for nPEP and in majority of countries, nPEP is never recommended  and in spite of estimations of HIV-transmission risks in occupational and non-occupational contexts being comparable, easy access to nPEP is not guaranteed for the general population.
| Occupational Exposure to HIV|| |
An occupational exposure is defined as a percutaneous, mucous membrane or non-intact skin exposure to blood or body fluids that occurs during the course of an individual's employment.  The risks for occupational transmission of HIV vary with the type and severity of exposure , [Table - 1],[Table - 2].
Potentially infectious body fluids 
Blood and visibly bloody body fluids are considered as potentially infectious. These include amniotic fluid, cerebrospinal fluid, breast milk, pericardial fluid, peritoneal fluid, pleural fluid, saliva in association with dentistry (likely to be contaminated with blood), synovial fluid, unfixed human tissues and organs, exudative or other tissue fluid from burns or skin lesions, vaginal secretions and semen. High concentration of free infectious virus and virus-infected cells have been reported in blood, genital fluids and cerebrospinal fluid.  Faeces, nasal secretions, saliva, sputum, sweat, tears, urine and vomitus are not considered potentially infectious unless they contain visible blood.
Factors affecting the risk for HIV transmission 
The average risk of HIV infection after percutaneous exposure to HIV-infected blood is 0.3%, but the factors that influence this risk are not well understood. In a case-control study, Cardo et al. found that risk of HIV infection after percutaneous exposure increases with a larger volume of blood and high-viral load in source patient's blood.  Other factors associated with increased risk of HIV transmission include depth of the injury, whether the device was visibly contaminated with blood, needle-hollow bore/solid (suture), treatment status of patient and duration of exposure.
| Non Occupational Exposure (nPEP)|| |
Non-occupational exposure is any direct mucosal, percutaneous or intravenous contact with potentially infectious body fluids that occurs outside perinatal or occupational situations, e.g., unprotected sexual exposure, sexual exposure involving a broken or slipped condom, injecting drug users (IDUs) sharing equipment, accidental needle stick injuries, bite wounds, mucosal exposure, cases where a patient is exposed by a health care worker (HCW) or another patient, etc. , As nPEP is not 100% effective in preventing transmission and because ART carry risk for ADR, nPEP should be used only for infrequent exposures. Persons who engage in behaviours that result in frequent, recurrent exposures (e.g., discordant sex partners who rarely use condoms or injection-drug users who often share injections) should not take nPEP. In these instances, exposed persons should instead be provided with intensive risk-reduction interventions. In addition percutaneous injuries from needles discarded in public settings may result in requests for nPEP, although no HIV infections from such injuries have been documented. In a study of syringes used to administer medications to HIV-infected persons, only 3.8% had detectable HIV RNA.  In a study of the viability of virus in needles, viable virus was recovered from 8% at 21 days when the needles had been stored at room temperature; <1% had viable virus after 1 week of storage at higher temperatures. 
Contrary to the popular belief that PEP for sexual exposure (PEPSE) increases the risk taking behaviour. Martin et al. reported that 336 cases receiving PEPSE, 74% reported a decrease in unprotected sexual exposure events at 6 months and 17% were treated with more than one course of PEP. 
| Risk Assessment|| |
Evaluation of exposure: An exposure incident should be evaluated for the type and quantity of body substance involved, the transmission route, the severity of the exposure, depth of injury and the recency of exposure.
Evaluation of the exposure source: Testing the source person for HIV along with pre- and post-test counselling or testing the suspected exposure material (blood, tissue, etc.) if the person is unavailable is recommended as soon as possible. Two positive ELISA or rapid HIV-antibody tests are considered to be highly suggestive of infection. The exposure source should also be tested for hepatitis C and B viruses (HCV and HBV).
Information to consider when evaluating an exposure source includes: Previous HIV test results and CD4 count; clinical symptoms suggestive of primary HIV infection, current stage of HIV, personal history suggesting possible exposure to HIV (multiple sexual partner, BT), history of high-risk behaviour or chronic illness in spouse and history of treatment, duration, type of regimen and adherence in source.
- If the exposure source is unknown, cannot be tested or refuses to be tested , the risk of HIV transmission should be assessed epidemiologically by type of exposure, prevalence of HIV in the population and risk assessment of the source person and of spouse of the source.
- If the source person is HIV negative and has no clinical evidence of HIV infection, no further testing of the source is indicated. The likelihood of the source person being in the "window period" of HIV infection with no symptoms of acute retroviral syndrome is extremely small. If none of the above-mentioned information is available, initiation of PEP, if indicated, should not be delayed. Appropriate changes in the PEP regimen can be made if new information emerges after PEP has been started.
The impact of drug resistance on the PEP decision: Known or suspected resistance of the source virus to ARV agents is a concern while making decisions about PEP. Beltrami et al. reported 16 (39%) of 41 source persons virus to be resistant to reverse transcriptase inhibitors and four (10%) to Protease Inhibitors (PIs).  There are more than 21 documented failures of PEP among HCWs due to drug-resistant HIV strains.  Perdue et al. reported occupational transmission of resistant HIV strains, despite PEP with combination drug regimens.  Resistance should be suspected in source persons when they are experiencing clinical progression or a persistently increasing viral load and/or decline in CD4 T-cell count, despite therapy. However, resistance testing of the source virus at the time of an exposure is not practical, because the results will not be available in time to influence the choice of the initial PEP regimen. Furthermore, no data exist to suggest that modification of a PEP regimen after receiving results from resistance testing (usually a minimum of 1-2 weeks) improves efficacy of PEP.  It makes intuitive sense that, in areas where drug resistance is common, a third drug in the regimen would help ensure that at least one drug is active against the potentially transmitted virus and selection of drugs to which the source person's virus is unlikely to be resistant is recommended by CDC.
Selection of resistant virus might occasionally result from the use of nPEP. However, because the majority of non-occupational exposures do not lead to HIV infection and because the use of combination ARV therapy might reduce further the transmission rate, such occurrences are probably rare. For patients who seroconvert despite nPEP, resistance testing should be considered to guide early and subsequent treatment decisions.
Evaluation of the exposed person 
It has to be done as soon as possible and includes the following:
- An HIV-serological baseline test to establish infection status at the time of exposure, with pre- and post-test counselling. The routine use of direct virus assays (e.g., an HIV p24 antigen assay or HIV RNA tests) to detect infection among exposure sources is usually not recommended because of unacceptably low-positive predictive value of these tests in these settings, window period of 24-48 h, the infrequency of occupational seroconversion, high cost and the high rate of false-positive results. 
- Baseline laboratory testing including complete blood count (CBC) with differential and platelets, liver function tests (LFTs), urea or serum creatinine and serological tests for HCV and HBV should be done.
Additional considerations for non-occupationally exposed people
In addition, those seeking nPEP should be evaluated for the following information:
- Frequency of exposures to HIV
- History of specific sexual, drug-injecting or other behaviours
- If an accidental needle-stick exposure, whether there was fresh blood and whether it was a deep injury or intravenous injection
- In case of sexual exposure: condom use, presence of STIs, need for emergency contraception or pregnancy testing (for females), presence of sexual assault, by one or more persons, whether menstruation or other bleeding was present at time of exposure.
| Clinical Management of People Incidentally Exposed to HIV|| |
First aid : It refers to the actions that should be taken immediately to reduce contact time with the infected body fluids and tissues and to clean the exposure site to reduce risk of infection. Wash the site immediately, using soap and running water for several minutes or until bleeding ceases. Do not use any strong solutions such as alcohol, bleach or iodine as they may irritate the wound and make the injury worse. Do not squeeze or rub or suck the injury site. For splash in the eye, irrigate the eye with water or normal saline. Do not use soap or disinfectant on the eye.
Counselling an exposed person
Counselling on risk-reduction; avoiding pregnancy and breastfeeding; avoiding blood, tissue or sperm donation; using condoms for sexual intercourse up to the sixth month test and the need for clinical and serological follow-up should be provided. Person should be informed about the strong need for adherence to PEP regimens.
Time of initiation and duration of PEP
Information about primary HIV infection indicates that systemic infection does not occur immediately, leaving a brief window of opportunity during which post-exposure ARV intervention might modify or prevent viral replication [Figure - 1]. In a primate model of simian immunodeficiency virus (SIV) infection, infection of dendritic cells occurred at inoculation site during the 24 h. Over the subsequent 24-48 h, migration of virus to regional lymph nodes occurred and virus was detectable in the peripheral blood within 5 days.  Theoretically, initiation of PEP soon after exposure might prevent or inhibit systemic infection. The PEP should be initiated within hours of exposure - ideally within 2 h and not later than 72 h after exposure and should not be delayed while waiting for test results and should be administered for 4 weeks if tolerated. 
Choosing an ARV regimen for PEP
For majority of exposures, two drug ARV regimen is considered to be sufficient  [Table - 3] and [Figure - 2]. However, suspected or proven drug resistance in a source person might guide a decision to prescribe a three ARV drug regimen , [Table - 4]. If a question exists concerning use of two-drug or three-drug regimen, start the two-drug regimen immediately and later on modify the regimen if needed. There are no published data that address the efficacy of two-drug and three-drug PEP regimens compared with one another and no evidence indicates that a three-ARV combination is more effective than a two-ARV combination. Some data suggest that there is significant toxicity associated with three-ARV regimens, while two-ARV combinations are generally well tolerated.  Starter packs (for 3-5 days) should be provided while considering nPEP in order to look for adherence and provide additional counselling on next visit.
ARVs not recommended for PEP
Some ARVs are not recommended for use in PEP because of a higher risk for potentially serious life-threatening events: nevirapine (NVP), abacavir (ABC), zalcitabine (ddC). , Amprenavir (APV) should not be given to pregnant or lactating women. In addition, EFV is not recommended because of low genetic barrier except when the exposed person cannot tolerate available boosted PIs or the source is infected with drug-resistant HIV that is sensitive to EFV.
A three drug regimen, often including a PI, have been associated with more frequent side effects. The most common short-term toxicities reported in the PEP registry of 492 HCWs included nausea/vomiting, fatigue, headache and diarrhoea.  The potential risks include serious adverse events attributed to nevirapine in three-drug regimens, including two cases of fulminant hepatitis, one of which required liver transplantation. Quirino et al.  compared the tolerability of three-drug PEP with that of three-drug therapy for HIV-infected patients and found that rates of ART toxicity were six times higher among PEP recipients (57%) than among HIV-infected patients (7%) and the rate of discontinuation of therapy among PEP recipients was eightfold higher than that among HIV-infected patients. Offering a two-drug regimen is a viable option, primarily because the benefit of completing a full course of this regimen exceeds the potential benefit of adding a third agent and risking non-completion.
| Considerations for Vulnerable Populations|| |
Pregnant women and women of childbearing potential
Because of potential teratogenicity, efavirenz should not be used in any nPEP regimen during pregnancy or among women of childbearing age at risk for becoming pregnant during the course of ARV prophylaxis. A protease inhibitor or nucleoside reverse transcriptase inhibitor-based regimen should be considered in these circumstances. Because the effect of efavirenz on hormonal contraception is unknown, women using such contraception should be informed of the need to use an additional method (e.g., barrier contraception). Because of the observed association with hyperbillirubinaemia, indinavir should not be administered before delivery. 
Potential HIV exposures in children occur most often by accident (e.g., needlesticks in the community, fights or playground incidents resulting in bleeding by an HIV-infected child) or by sexual abuse or assaults. In Thailand, during 2000-2003, 1365 children were counselled and 1205 consented to HIV testing and HIV-PEP. Forty-five percent met the criteria for HIV-PEP, but only 15% completed the full 28-day-course of HIV PEP and follow up at 6 months was also low, just 27%.  Adherence to the prescribed medications will depend on the involvement of and support provided to parents or guardians. Medication dosage must be altered according to the weight of the child and acceptable paediatric formulations should be prescribed so as to increase adherence.
Sexual assault survivors
Use of nPEP for sexual assault survivors has been widely encouraged both in the United States and elsewhere. Sexual assault is common among women: 13% of a national sample of adult women reported having ever been raped and 5% reported having been raped more than once in United States.  However, only three documented cases of HIV infection resulting from sexual assault have been published.  Sexual assault typically has multiple characteristics that increase the risk for HIV transmission if the assailant is infected. In one prospective study of 1076 sexual assault cases, 20% were attacked by multiple assailants, 39% were assaulted by strangers, 83% of females were vaginally penetrated and 17% overall were sodomised. Genital trauma was documented in 53% and sperm or semen was detected in 48%.  Despite these risks and the establishment of multidisciplinary support services, sexual assault survivors often decline nPEP and many who do take it do not complete the 28-day course. In Vancouver, 71 of 258 assault survivors accepted the 5-day starter pack of nPEP, 29 returned for additional doses and 8 completed 4 weeks of therapy.  These patients will benefit from supportive services to improve adherence to nPEP.
Follow-up of exposed persons
All patients seeking care after HIV exposure should be tested for HIV at baseline and at 4-6 weeks, 3 and 6 months after exposure. In addition, testing for sexually transmitted diseases, hepatitis B and C and pregnancy should be offered. Patients should be instructed about the signs and symptoms of acute retroviral infection. Direct virus assays may be performed on any exposed person who has an illness compatible with an acute retroviral syndrome, regardless of the interval since exposure. Transient, low-grade viraemia has been observed in humans exposed to HIV who were administered PEP  and did not become infected. In certain cases, this outcome might represent aborted infection rather than false-positive test results, but this can be determined only through further study. In addition, monitor haemoglobin, liver function and renal function. Patients should be followed up for adherence and possible side-effects of ARVs should be managed symptomatically without changing the regimen.
Prevention of occupational and nosocomial exposure
The importance of primary prevention in any setting where HIV can be transmitted should be reinforced in every programme that provides PEP. HCW and other exposed workers should receive appropriate information on PEP availability and the reference centres. It is important to underline that PEP is not ever likely to be 100% effective and thus it should always be integrated into a larger HIV exposure prevention strategy based on standard precaution principles. Quality control and evaluation of safety conditions at work should be re-evaluated after exposure. Provided that the procedures for preventing occupational transmission of blood borne viruses are adhered to at all times, most clinical procedures pose no risk of transmission of HIV from an infected HCW to a patient. 
All blood and other body fluids should be regarded as potentially infectious and universal precautions should be followed all the time. The overall risk of an infected HCW transmitting HIV to a patient is low and worldwide, only two possible reports of such transmission have been reported, both during exposure-prone procedures.
Universal precautions should be followed that includes:
- Wash hands immediately if contaminated with body fluids.
- Wear gloves when contamination with body substances is anticipated.
- Protective eyewear and mask should be worn when splashing with body substance is anticipated.
- All HCW should take precautions to prevent injuries during procedures and when cleaning or during disposal of needles and other sharp instruments.
- Needle should not be recapped.
- Needles should not be purposely bent or broken by hand, nor removed from the disposable syringe or manipulated by hand.
- After use, disposable syringes and needles, scalpel blades and other sharp items should be placed in a puncture-resistant container.
- HCW who have exudative lesions or dermatitis should refrain from direct patient care and from handling equipments.
- Clean and disinfect blood/body substances' spills with appropriate agents.
- Adhere to the disinfection and sterilization standards.
- Regard all waste soiled blood/body substance as contaminated and dispose off according to relevant standards.
- Vaccinate all clinical and laboratory workers against hepatitis B., other measures like double gloving, changing surgical techniques to avoid 'exposure prone' procedures use of needle - less systems and other safe devices should be encouraged.
HCW at all levels are occupationally exposed to hazards of infections like HIV, HBV, HCV. With an increasing HIV positive population and non-feasibility of subjecting all cases to HIV testing, risk of HIV transmission through occupational exposures is a real threat.
The need of the hour is to emphasize the potential of HIV transmission in hospital setup and to create awareness about PEP among HCW. nPEP can be offered for cases like sexual assault survivors. It is of utmost importance to correctly and consistently follow universal precautions.
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[Figure - 1], [Figure - 2]
[Table - 1], [Table - 2], [Table - 3], [Table - 4]