Infection caused by the Human Immunodeficiency Virus (HIV), almost five decades after notification of the first cases, remains a worldwide public health problem, despite all the advances achieved in the treatment and expansion of prevention strategies. It is estimated that approximately 37.9 million people live with HIV worldwide by the end of 2018 .
In Brazil, in 2018, 43.941 new cases of HIV infection and 37.161 cases of AIDS were reported, totaling 966,058 AIDS cases detected in the country . Since 1996, the country has offered antiretroviral treatment through the Unified Health System (SUS) for People Living with HIV (PLHIV) and was one of the pioneer countries among low and middle incomes. From 2013, SUS guarantees treatment for all PLHIV, regardless of the stage of the disease and the CD4 T lymphocyte count. More than thirty years after the first case, the epidemic continues to expand. New infection rates have remained persistently high over the past decade, with an estimated 48,000 new HIV infections per year, even with coverage of antiretroviral treatment (ART) in SUS .
The rate of AIDS detection has decreased in Brazil in recent years in the Southeast, South, and Midwest regions, while in the North and Northeast regions, they have shown an increasing trend in detection . HIV infection in the Brazilian population has an estimated prevalence rate of 0.4%. However, the epidemic disproportionately affects key populations as women sex workers, men who have sex with men, and transgender women .
The main route of HIV transmission is sexual, among people aged 13 and over, in 2018 in all regions, both men (78.9%) and women (86.9%) . In the early years of the HIV epidemic, condom use was practically the only method of preventing sexual transmission of HIV widely recommended and widespread throughout the historical path of the epidemic . Condoms have advantages in low cost, easy access, and low adverse effects when they are adopted consistently and correctly. Besides, they effectively prevent other sexually transmitted infections  and are considered fundamental to a comprehensive approach to prevention .
However, this strategy does not eliminate the risk of HIV transmission. A systematic review study showed that the consistent use of condoms (for all acts of vaginal penetration) in heterosexual relationships results in an 80% reduction in the incidence of HIV  and 70% among male homosexuals (for anal sex) . Studies have also shown inconsistent condom use among partners living with HIV and relating to HIV-negative people or with unknown HIV status [6,10].
A study conducted in Brazil identified that PLHIV undergoing clinical-outpatient follow-up who had less education, multiple sexual partners, using alcohol or other drugs, do not receive advice from a healthcare professional. They have no knowledge of treatment as prevention. Not knowing that undetectable viral load reduces the risk of human immunodeficiency virus transmission was associated with inconsistent condom use , which reflects the difficulty in accessing health information to assimilate the orientations received and to change health behavior.
Also, aspects related to social gender norms determine a low power of sexual negotiation for Brazilian women making them more likely to have unprotected sex. Despite the advancement of feminist movements, women's role in sexuality and their responsibility for reproductive issues hinders dialogue with their partners and increases vulnerability .
Gender-based violence reduces engagement for women living with HIV at multiple care continuum levels . It might be a particularly salient issue for the Latin American region, where high rates of intimate partner violence, sexual assaults, and femicide have been documented [13, 14].
Therefore, important advances in the field of HIV prevention have provided paradigm shifts with the implementation of combined biomedical, behavioral, and structural interventions . Combined prevention is a broader concept that combines different prevention methods that can interfere with the sexual transmission of the virus, with the use of antiretrovirals, including Pre-Exposure Prophylaxis (PrEP) and Post-Exposure Prophylaxis (PEP), termed as biomedical interventions. Such strategies have been considered to be effective in reducing the risk of HIV transmission and are part of combined prevention .
As a result of advances in HAART, post-sexual exposure to HIV prophylaxis (PEP) was implemented in 2012, is a method used in situations where sexual exposure to HIV occurs, especially when the sexual act was performed in the absence of condoms, or in times of condom failures, such as breakage or problems with structural characteristics due to inappropriate use. Their use can reduce the risk of acquiring the infection through a therapeutic regimen with antiretrovirals .
PrEP was implemented in Brazil by the public health system on December 1, 2017  and is an important advance in prevention and is used before exposure to the virus, recommended for homosexuals, men who have sex with men (MSM), transgender, sex workers, people who use drugs, those who are incarcerated, serodiscordant partnerships, taking into account also the repetitions of anal and/or vaginal sexual practices with penetration without the use of condoms, frequency of sexual relations with casual partners, quantity and diversity of sexual partnerships, contexts of transactional sex (for money, valuables, housing, drugs, among others), history of sexually transmitted infections and repeated search for post-exposure prophylaxis (PEP) [17-19].
Although these two biomedical interventions based on drug treatment are considered essential for prevention, there are gaps in the knowledge of both HIV-negative/unknown people and among PLHIV. When revisiting studies that investigated the awareness of PrEP and PEP, it was found that the levels were below expectations. Even with the release of the use of PrEP in the United States . Similar results were observed among Nigerian university students . In Canada, MSM demonstrated incipient knowledge about PrEP, including those who were HIV-negative and HIV-positive .
To achieve relevant results in HIV prevention, through the use of such strategies, it is necessary to expand awareness and use education actions, focusing on people most exposed to the virus , such as sexual partners, whether fixed or casual, of PLHIV. Besides, expanding education actions for the general population may contribute to adherence to HIV prevention methods.
In general, knowledge about PrEP and PEP is surprisingly low, both in developed countries [21-23] and in developing countries, as in Brazil . However, studies conducted in three countries in Latin America and the United States of America show that interest in using PrEP is high among key populations [5,24].
Antiretroviral drugs, used as antiretroviral therapy (ART) and PrEP, are powerful HIV prevention tools for HIV serodiscordant couples. Although the HIV prevention effectiveness of ART and PrEP is proven, the prevention benefits are only realized when adherence is high . Also, the residual risk of HIV transmission persists during the first six months of ART, with incomplete viral suppression in blood and genital compartments. For HIV-serodiscordant couples in which the infected partner is starting ART, other prevention options are needed, such as pre-exposure prophylaxis, until viral suppression is achieved .
In this context, current World Health Organization  guidelines recommend ART for all HIV positive adults diagnosed with HIV and PrEP as part of the HIV prevention combination for people at substantial risk of HIV, including HIV negative partners of couples. Due to the scarcity of studies that address the theme in Brazil, this study aimed to analyze the factors associated with the knowledge of PEP and PrEP as secondary prevention among people living with HIV/AIDS to improve policies for the implementation and distribution of strategies in a broader prevention plan among people at risk of infection.