and made similar recommendations for its use among men and transgender women who have sex with men. the who noted that "international scientific consensus is emerging that antiretroviral drugs, including prep, significantly reduce the risk of sexual acquisition and transmission of hiv regardless of population or setting.": 8, 10, 11 in 2014, on the basis of further evidence, the who updated the recommendation for men who have sex with men to state that prep "is recommended as an additional hiv prevention choice within a comprehensive hiv prevention package.": 4 in november 2015 the who expanded this further, on the basis of further evidence, and stated that it had "broadened the recommendation to include all population groups at substantial risk of hiv infection" and emphasized that prep should be "an additional prevention choice in a comprehensive package of services." as of 2018, numerous countries have approved the use of prep for hiv/aids prevention, including the united states, south korea, france, norway, australia, israel, canada, kenya, south africa, peru, thailand, the european union and taiwan. new zealand was one of the first countries in the world to publicly fund prep for the prevention of hiv in march 2018. funded access to prep will require that people undergo regular testing for hiv and other sexually transmitted infections, and are monitored for risk of side effects. people taking funded prep will receive advice on ways to reduce the risk of hiv and sexually transmitted infections. in australia, the country's therapeutic goods administration approved the use of truvada as prep in may 2016, allowing australian providers to legally prescribe the medication. on march 21, 2018, the federal minister for health announced that prep will be subsidized by the australian government through the pharmaceutical benefits scheme (pbs) from april 1, 2018. availability and pricing in the united states a bottle of 200 mg/25 mg emtricitabine and tenofovir alafenamide used for prep under the brand descovy, developed by gilead sciences. within the united states, truvada and descovy are brand name products of gilead sciences that cost around $2200/month (a 30-day supply) at wholesale price. in other countries around the world, generic truvada is available for a much lower price. expected fall of 2020, teva pharmaceuticals will begin producing a generic version of truvada within the united states; however, it has been reported that the details surrounding the rights to the patent are unclear, which makes it difficult to predict if this will increase access to the medications. in the meantime, there are several assistance programs at the local, state, and national level for gaining access to prep at reduced costs. gilead has an "advancing access" co-pay coupon program that can be accessed by individuals and providers alike to help cover some of the monthly costs of these medications. it is recommended to discuss other available options with a community pharmacist or physician. in december 2019, the u.s. announced the ready, set, prep program to provide free prep to the uninsured through major drugstore chains. the ready, set, prep program is led by the u.s. department of health and human services (hhs) and allows qualifying individuals to fill their prescription for prep medication free of cost at their choice of participating pharmacies or through the mail. npin prep provider data and locator widget was launched on the cdc website to provide a comprehensive, national directory of public and private providers in the u.s. that offer pre-exposure prophylaxis (prep) to prevent hiv infection. the database includes over 1,800 prep providers from all 50 u.s. states as well as u.s. territories. beginning in january 2020, after california governor gavin newsom signed senate bill 159 (sb159) in late 2019, licensed pharmacists in california are authorized to initiate and dispense a 30 to 60 day supply of pre-exposure prophylaxis (prep) or the full course of post-exposure prophylaxis (pep) without a doctor's prescription, given certain clinical criteria of the individual are met. the bill acts as an extension of medi-cal benefits (the medicaid program in the state of california). the law is recognized by pharmacist organizations, health providers, legislators, and the general public to be the removal of a barrier to direct and time-dependent access to these medications, especially for those in communities most affected by hiv/aids. politics and culture since the fda approval of prep for the prevention of hiv, moves toward greater adoption of prep have been met some issues, especially around the overall public health effect of widespread adoption, the cost of prep and associated disparities in availability and access. many public health organizations and governments have embraced prep as a part of their overall strategy for reducing hiv. for example, in 2014 new york state governor andrew cuomo initiated a three-part plan to reduce hiv across new york that specifically emphasized access to prep. similarly, the city of san francisco launched a "getting to zero" campaign. the campaign aims to dramatically reduce the number of new hiv infections in the city and relies on expanding access to prep as a key strategy for achieving that goal. public health officials report that since 2013 the number of new hiv infections in san francisco has decreased almost 50% and that such improvements are likely related to the city's campaign to reduce new infections. additionally, numerous public health campaigns have been launched to educate the public about prep. for instance, in new york city in 2016 gay men's health crisis launched an ad campaign in bus shelters across the city reminding riders that adherence to prep is important to ensuring the regimen is maximally effective. in washington, d.c., a prep campaign was launched to increase the number of d.c. residents taking prep. social media pushes, such as an ad campaign called "prep for her", targeted african-american women, who, along with gay and bisexual african-american men, are at high risk of infection in the district. other states and cities that have initiated "getting to zero" campaigns include massachusetts, connecticut, illinois, san diego, silicon valley/santa clara, and miami-dade. despite those efforts, prep remains controversial among some who worry that widespread prep adoption could cause public health issues by enabling risky sexual behaviors. for instance, aids healthcare foundation founder and director michael weinstein has been vocal in his opposition to prep adoption, suggesting that prep causes people to make riskier decisions about sex than they would otherwise make. some researchers, however, believe that there is insufficient data to determine whether or not prep implementation has an effect on the rate of other sexually transmitted infections. other critics point out that despite implementation of prep, significant disparities exist. for example, some point out that african americans bear a disproportionate burden of hiv infections but may be less likely than whites to access prep. still other critics of prep object to the high cost of the regimen. for example, the u.k.'s nhs initially refused to offer prep to individuals citing concerns about cost and suggested that local officials ought to bear the responsibility of paying for the drug. however, following significant advocacy efforts, the nhs has started to offer prep to people in the uk in 2017. impact on the culture of men who have sex with men prep is used predominantly by men who have sex with men, often as an alternative to condoms. for the first time since the outbreak of the aids crisis, prep makes somewhat hiv-protected sex without condoms possible, and since its availability, sex without condoms has increased. prep does not prevent the transmission of sexually transmitted infections other than hiv, and is not 100% effective. barriers to use prep is underused. a systematic review of 76 peer-reviewed articles and 28 conference abstracts of values and preferences among global populations who might benefit from prep found that awareness of prep is low, but individuals were receptive to use when presented with information. common barriers to prep use include lack of communication between an individual and their doctor, stigmatization, concerns about safety, side effects, and cost and effectiveness. transgender women are disproportionally affected by hiv/aids, and prep is often underused. barriers for prep use and access for transgender women include concerns about side effects, cost, hormone therapy, adherence, prep-related stigma and interaction with healthcare workers. studies evaluating prep efficacy to reduce risk of hiv infection found a linear relationship between adherence and effectiveness of medication. this means that the more closely people follow recommended dosing of prep, the more effective the medication is at preventing infection. research most prep studies use the drug tenofovir or a tenofovir/emtricitabine combination (truvada) that is delivered by mouth. initial studies of prep strategies in non-human primates showed a reduced risk of infection among animals that receive arvs prior to exposure to a simian form of hiv. a 2007 study at ut-southwestern (dallas) and the university of minnesota showed prep to be effective in "humanized" laboratory mice. in 2008, the iprex study demonstrated 42% reduction of hiv infection among men who have sex with men, and subsequent analysis of the data has suggested that 99% protection is achievable if the drugs are taken every day. below is a table summarizing some of the major research studies that demonstrated prep with truvada to be effective across different populations. prep approaches with agents besides truvada are being investigated. on december 20, 2021, the fda approved cabotegravir (apretude), which was the first injectable drug for prep that's taken every two months. there has been some evidence that other regimens, like ones based on the antiretroviral agent maraviroc, could potentially prevent hiv infection. similarly, researchers are investigating whether drugs could be used in ways other than a daily pill to prevent hiv, including taking a long-acting prep injection, prep-releasing implants, or rectally administered prep. however, it is important to keep in mind that as of 2017, major public health organizations such as the u.s. centers for disease control and prevention (cdc) and the world health organization (who) recommend only daily truvada for use as prep. data on efficacy and safety of prep in adolescents are insufficient. risks and benefits of prep use should be considered for adolescents. studytypetype of prepstudy populationefficacy percent of patients who took medication (adherence) caprisa 004double-blind, randomizedpericoital tenofovir gelsouth african females39% reduction of hiv infection 72% by applicator count iprexoral emtricitabine/tenofovirmen who have sex with men and transgender women42% reduction of hiv infection. 99% reduction estimated with daily adherence 54% detectable in blood partners preporal emtricitabine/tenofovir; oral tenofovirafrican heterosexual couplesreduction of infection by 73% with truvada and 62% with tenofovir 80% with truvada and 83% with tenofovir detectable in blood tdf2oral emtricitabine/tenofovirbotswana heterosexual couples63% reduction of infection 84% by pill count fem-preporal emtricitabine/tenofovirafrican heterosexual femalesno reduction (study halted due to low adherence) <30% with detectable levels in blood voice 003oral emtricitabine/tenofovir; oral tenofovir; vaginal tenofovir gelafrican heterosexual femalesno reduction in oral tenofovir or vaginal gel arms <30% with detectable levels in blood bangkok tenofovir studyrandomized, double-blindoral tenofovirthai male injection drug users48.9% reduction of infection 84% by directly observed therapy and study diaries ipergayrandomized, double-blindoral emtricitabine/tenofovirfrench and quebecois gay males86% reduction of infection (video summary) 86% with detectable levels in blood proudrandomized, open-labeloral tenofovir-emtricitabinehigh-risk men who have sex with men in england86% reduction of hiv incidence hptn 083randomized, double-blindcabotegravir versus emtricitabine/tenofovirtransgender women and cisgender men who have sex with men in argentina, brazil, peru, thailand, the u.s., vietnam, and south africa.highly efficacious compared to daily oral tdf/ftc. discover study randomized, double-blind oral tdf/ftc versus taf/ftc high-risk men who have sex with men in europe, north and south america taf/ftc was non-inferior with more favorable bone and kidney outcomes possibility of increased risk-taking while prep appears to be extremely successful in reducing hiv infection , there is mixed evidence that there might be a change in use of condoms in anal sex, raising risks of spreading sexually transmitted infections other than hiv. in a meta-analysis of 18 studies, researchers found that rates of new diagnoses of stis among msm (men who have sex with men) given prep were 25.3 times greater for gonorrhea, 11.2 times greater for chlamydia and 44.6 times greater for syphilis, compared with the rates among msm not given prep. unlike hiv, these three stis can be cured with antibiotics. however, the increased rates of such infections and their treatment can lead to antibiotic-resistant mutations of the pathogens; antibiotic-resistant gonorrhea is already a major concern.