We performed a digital marketing campaign targeting MSM from March 2018 to October 2019 using advertisements on GSN apps (Hornet and Grindr) and social media (Facebook and Instagram) to increase HIV knowledge, HIV testing, and PrEP awareness. The Instituto Nacional de Infectologia Evandro Chagas, Fundação Oswaldo Cruz (INI-Fiocruz) study team designed and implemented the campaign [16]. INI-Fiocruz has the largest HIV prevention service for adults (18 years or older) in Rio de Janeiro city and its metropolitan area in Brazil. The service is part of the Brazilian Public Health System (Sistema Único de Saúde [SUS]) at no cost to the user.

Hornet and Grindr are popular among MSM in Brazil, and recruitment using these GSN apps has been used in previous cross-sectional studies conducted in the country [5,9,13,14,17,18]. We used direct inbox messages and banners to advertise on Hornet and Grindr, respectively. In addition, we created posts on social media (Facebook and Instagram), which were boosted and appeared at user’s feeds. We targeted social media users interested in subjects related to LGBTQIA+ people (people of diverse genders and sexualities, inclusive of and not limited to lesbian, gay, bisexual, transgender, queer, intersex, asexual, questioning, and pansexual) communities. Advertisement messages were built during meetings with key members of MSM communities from different socioeconomic status and race. These advertisements had information about HIV prevention and invited viewers to contact a peer educator (via phone number, email, and WhatsApp) to schedule a visit at the HIV prevention service for HIV risk assessment, HIV testing and referral to PrEP or postexposure prophylaxis (PEP).

All MSM referred by the peer educator who attended the HIV prevention service answered semistructured interviews conducted by trained counselors. Covariables were age at the time of the visit (categorized in 18-24, 25-35, and >35 years); race (Black, Pardo or mixed, and White); schooling (elementary [≤9 years], secondary [10-12 years] and postsecondary [>12 years]) and Municipal Human Development Index, a 3-level dimension measure of human development (life expectancy, education, and income), dichotomized into very high (≥0.800) or other (<0.800) [19].

HIV testing was offered to all individuals who attended the HIV prevention service. HIV status was dichotomized into negative and positive according to HIV rapid test results, following Brazilian recommendations [20]. Counselors evaluated all HIV-negative MSM for PEP and PrEP eligibility based on Brazilian National Guidelines. Individuals reporting condomless sex in the previous 72 hours were referred for PEP [21]. MSM with at least one of the following criteria in the last 6 months were eligible for PrEP: (1) condomless receptive anal sex, (2) sex with partner living with HIV, (3) transactional sex (in exchange for money, goods, and benefits, among others), and (4) history of STI [22]. PrEP uptake was defined as the number of participants who initiated PrEP divided by the number of participants eligible for PrEP [23].

We evaluated the web-based recruitment cascade for Hornet, Grindr, and social media based on the number of MSM who (1) viewed the advertisement; (2) contacted the peer educator; and (3) attended the HIV prevention service. Conversion rate was calculated dividing the number of MSM who contacted the peer educator by those reached by advertisements. We used chi-square test to compare the characteristics of MSM recruited through dating apps (Hornet and Grindr) with those of MSM recruited by social media (Facebook and Instagram). We estimated the advertisement costs (in US dollars) to recruit one participant to HIV prevention service by dividing total advertisement costs by the number of individuals who attended the service (GSN apps or social media). Lastly, we used the same rationale to estimate the cost per individuals engaging on PrEP. All analyses were conducted in R Studio, using R version 4.0.3 (R Foundation for Statistical Computing).

This study was reviewed and approved by the INI-Fiocruz institutional review board (#CAAE 26095519.1.0000.5262). The board waived the informed consent as data were collected retrospectively from participants’ charts and exams collected at INI-Fiocruz during HIV testing or prevention routine. Most participants attended the service only once, and personal information such as telephone number or address were nonexistent or outdated, avoiding collection of informed consent a posteriori.

Our digital marketing campaign on different web-based venues was effective in recruiting MSM to a large HIV prevention service in Brazil. We successfully reached and engaged diverse MSM of different ages and races and high PrEP eligibility. Nevertheless, MSM with lower education was the least accessed group, indicating that complementary recruitment strategies such as those on LGBTQIA+ venues or respondent-driven sampling [24] may still be necessary to reach MSM at higher social vulnerability.

Social media recruited a larger proportion of young MSM, with lower income and schooling compared to those recruited via GSN apps. This underscores the importance of using social media to recruit MSM for HIV prevention services and to promote prevention campaigns targeting young MSM at HIV risk in Rio de Janeiro, Brazil. In addition, social media were more cost-effective to recruit individuals to attend the HIV prevention service and to use PrEP. Facebook was the most cost-effective web-based venue to recruit MSM to a qualitative study in Seattle [25] and was effective to recruit Latino gay couples in a study conducted in New York [26]. These findings confirm that social media platforms such as Facebook and Instagram could be used as an alternative option to reach and engage MSM in other HIV prevention services in resource-constrained settings such as Brazil.

By contrast, a study conducted in Philadelphia identified Grindr as the most effective strategy to recruit people for an HIV vaccine trial [27]. Although PrEP uptake did not differ between individuals recruited by different strategies, GSN apps were more effective in recruiting high-risk MSM, according to PrEP eligibility, compared to social media. As such, different web-based venues may be useful to recruit diverse MSM to HIV prevention services, especially young MSM, as shown in previous studies conducted in the United States [27,28].

In addition to recruitment to the HIV prevention service, our campaign aimed to increase PrEP awareness, although the latter could not be measured in this study. Data from web-based surveys showed an increase in PrEP awareness in Rio de Janeiro, Brazil, from 2016 to 2018 [29], and 2020 national data indicated that 87% of sexual and gender minorities recruited on Hornet were aware of PrEP [9]. Moreover, HIV knowledge was associated with PrEP use among MSM eligible for PrEP in Brazil [17]. Digital campaigns are of utmost importance to promote information on HIV prevention, including PrEP and other prevention technologies, among MSM. These results are particularly useful to develop public strategies and may contribute to designing campaigns to increase PrEP uptake in Brazil. Lastly, our study was conducted before the COVID-19 pandemic, and due to the increased use of digital recruitment for scientific studies [30], a more heterogeneous population would be expected to be reached nowadays.

This study considered only MSM reached by a digital marketing campaign who contacted the peer educator. The advertisements may have reached other MSM who attended the HIV prevention service without contacting the peer educator or who attended other services in Rio de Janeiro, Brazil. Responses of web-based recruitment and PrEP or PEP eligibility were self-reported, thus introducing the possibility of recall, response, or social desirability bias. Participants reported sexual behavior during risk assessment for PrEP or PEP evaluation. However, data on sexual behavior practices have not been systematically collected, preventing further associations between web-based recruitment and sexual practices (eg, condomless receptive sex or transactional sex). This study helped to identify this issue, leading to modifications aiming to collect more detailed data on sexual behavior and other variables, such as substance use and previous STIs. Lastly, venue-based recruitment and peer referral may perform better than web-based recruitment for most vulnerable MSM (young, Black or Pardo, low-income, and low-educated individuals) [16], highlighting the importance of community networks.

Advertisements on social media and GSN apps were useful to disseminate information on HIV prevention strategies and to recruit MSM to an HIV prevention service in Brazil. Compared to GSN apps, social media advertisements were less expensive and reached more vulnerable and younger MSM. Our findings indicate that digital marketing campaigns should use different and complementary digital venues to reach diverse MSM.