To reduce HIV infections in the US, the Centers for Disease Control and Prevention (CDC) is pursuing High-Impact Prevention (HIP) approaches. These methods include combined biological and behavioral interventions that are evidence-based, cost-effective, and often tailored for specific populations and geographic contexts. Key to achieving the greatest impact on the reduction of new HIV infections is the promotion of two highly effective biomedical interventions:

• Treatment as Prevention (TasP) Significant research data shows that antiretroviral therapy (ART), while sustaining the health of PLWH, also results in the prevention of HIV infections. When the HIV-positive person is virally suppressed, analyses of thousands of couples and acts of condomless sex, HIV transmissions to an HIV-negative partner do not occur. ART results in viral suppression, defined as less than 200 copies/ml. Obtaining viral suppression (or an undetectable viral load) on ART, prevents sexual HIV transmission (CDC 2014c). The CDC formally embraced this science in September 2017, and many other researchers and organizations have now embraced the Prevention Access Campaign’s U=U (HIV Undetectable = Untransmittable) [http://www.thelancet.com/pdfs/journals/lanhiv/PIIS2352-3018(17)30183-2.pdf].
   
• The uptake of pre-exposure prophylaxis (PrEP) among at-risk individuals. Older adults with HIV, in conjunction with their care providers, can serve as an effective contact point for the uptake of PrEP among their HIV-negative partners who are at risk for HIV infection.

The CDC provides clinical guidelines recommending PrEP as an evidence-based intervention to prevent HIV transmission (CDC 2014c). Multiple clinical trials have demonstrated the efficacy of PrEP (Treston 2015; Caceres 2015). In 2012, the Food and Drug Administration approved tenofovir + emtricitabine (TDF/FTC, Truvada) for use as PrEP in adults (CDC 2014c). This regimen consists of one pill taken once per day. When taken consistently, it has demonstrated a high level of protection against HIV infection.

How does PrEP fit in the health management of older adults with HIV? Health care providers, with their patients, have the opportunity to increase the uptake of PrEP in what are perceived as hard-to-reach at-risk groups. Unfortunately, no studies have focused specifically on PrEP use in older adults, although some clinical cohorts in San Francisco, included patients in their late 60s (Volk 2015).

Without more data, it is difficult to know if older adults may be at increased risk of toxicity from PrEP, which is a concern raised by many providers as older adults are already at increased risk for osteoporosis and decreased age associated renal clearance. Some data has suggested adults over age 50 may be at increased risk of renal toxicity [https://www.projectinform.org/news/croi-2016-serious-kidney-problems-are.... The CDC guidelines do not recommend PrEP for patients with chronic kidney disease (CrCl <60). For now, providers should follow current guidelines for monitoring toxicity. The CDC does not recommend routine DEXA screens before initiating PrEP (CDC Guidelines 2014).

Reasons to support PrEP use in older adults:

• In 2015 the CDC reported that 21% of all new HIV infections occur in people age 50 and older (CDC 2015b).
   
• Most people engage in sex with peers within their own age group.
   
• Condom use declines with age and is used by less than 10% of those over age 50 (MacDonald 2015).
   
• 15 to 20% of older adults living with HIV engage in high-risk (unprotected) insertive sex.
   
• In multiple studies, older adults with HIV report that their aged peer partners are often not capable of using a condom, due to the inability to sustain an erection (Guaraldi 2015; Glaude-Hosch 2015; Ford 2015a; Ford 2015b).
   
• Many older women with HIV report that they and their male partners do not perceive the need to use a condom because they cannot become pregnant. In all cases only condoms can prevent STIs (Pilowsky 2015); Nevedal 2015).

Given this information, older adults with HIV, working with their care providers, can convey to their sexual partners the need to consider the use of PrEP. In addition, given this information, primary care providers need to engage in sexual history taking with older adults and determine risk. This significant degree of access should be leveraged by primary care providers, not only as a way to deliver the details of PrEP use, but also as an opportunity for the provider to engage the older patient in often avoided discussion about sexual health issues.

A seminal study found that 18% of older adults with HIV were engaging in condomless sex with HIV-negative partners (Golub 2010). Although older adults often have sexual relations more with age-matched peers (Slater 2015), several studies have shown that there is a significant amount of high-risk behavior occurring between younger and older individuals (Mustanski 2013; Coburn 2010). For the older adult with HIV who is having sex with a younger person, the opportunity to encourage the use of PrEP is evident.

Ending the AIDS Epidemic

A detailed comprehensive report developed as part of the NEW YORK STATE ENDING THE EPIDEMIC effort, Older Adults (50+) and HIV Advisory Group Report Older Adult Implementation Strategies (OAIS) (NYS 2016) addresses PrEP in the context of older adults living with HIV. The report details reasons for offering PrEP to older adults:

• Half of men aged 40 years and older have erectile dysfunction, making condom use problematic to protect against HIV.
   
• Research finds few older men or women use condoms.
   
• Providers are not routinely discussing sexual health with older patients leaving at-risk patients undiscovered.
   
• Older women encounter challenges negotiating condom use with partners. The insistence of condom use is often perceived as implying the partner is gay, IDU, or HIV+). This may create situations of domestic/elder abuse. PrEP allows older women to be empowered about their sexual health.
   
• HIV testing rates among adults over 50 are very low. Encouraging PrEP can increase HIV testing rates in this group.

The report (NYS 2016) details implementation strategies whereby one can connect high-risk negative older adults to HIV prevention efforts including PrEP. These include targeted messaging and promoting education of medical and non-medical providers on the application of PrEP. Targeting must consider those locations where older adults assemble or derive day to day information. These may be conventional sources like newspapers, radio, TV, etc.) or social media as well as senior centers, CBOs providing social services, or age specific communities. Further, it is essential that images of older adults are represented in social messaging campaigns (Karpiak 2017).

Older adults with HIV, with the support of providers, can be effective advocates for the use of PrEP among their seronegative, at-risk sexual partners, be they casual, short-term, or long-term. Many of these at-risk partners are also among those least likely to be routinely tested for HIV. The use of PrEP together with “treatment as prevention” and other prevention interventions (condoms and behavioral interventions) is considered to be an important path toward ending the AIDS epidemic.