Abstract
Men who have sex with men (MSM) are the group at highest risk for HIV in China. Researchers have used various recruitment methods to reach this population hidden from the hetero-normative culture. To inform future recruitment strategies, we compared estimates of socio-demographic characteristics, HIV risk behaviors, depression, and intimate partner violence (IPV) across three samples of MSM and money boys in Shanghai, China. Data were collected from three community-based samples of MSM and money boys (n = 1352) recruited via respondent-driven sampling (RDS) (n = 404), community popular opinion leaders (CPOL) (n = 385), and Internet and venue-based sampling (VBS) (n = 546). Different recruitment methods generated samples with statistically significant differences among a number of socio-demographic characteristics, sexual behaviors, drug use, depression scores, and exposure to IPV. Specifically, RDS participants had lower education (p = .002), income levels (p < .001), and were more likely to report condomless sex with a woman (p < .001). CPOL participants were younger (p < .001), more likely to report lifetime condomless anal sex (p = .009), more than 10 male partners in the past 30 days (p < .001), and were less likely to experience violence by a male intimate partner (p = .001). VBS participants had lowest depression score (p = .005) and were more likely to report lifetime drug use (p = .003). Our findings reinforce that each recruitment method may reach a sub-group of MSM with a specific risk profile, so multiple methods may be needed to obtain a representative sample of MSM. Interventions may use specific recruitment methods to target certain segments of the MSM population.
Keywords: MSM, China, recruitment
Introduction
Like men who have sex with men (MSM) in other countries, MSM in China are disproportionately affected by HIV. MSM are currently the group at highest risk for HIV in China – a 2009 national, 61-city survey found that 5.0% of MSM were infected with HIV (State Council AIDS Working Committee Office, 2012; Wu et al., 2013). A sub-population of Chinese MSM, known colloquially as “money boys”, who engage in commercial or transactional sex, may be under even higher risk of infection. A 2012 meta-analysis estimated that HIV prevalence among this sub-population was 6.0% (4.2–8.5%) (Chow, Iu, Fu, Wilson, & Zhang, 2012). Furthermore, many money boys are also migrants who lack social support resources, access to the healthcare system, and have been shown to be at high risk of substance use and contracting HIV and other sexually transmitted infections (STI) (Chow et al., 2014; He, Wong, Huang, Ding, et al., 2007; He, Wong, Huang, Thompson, & Fu, 2007; Huang et al., 2012; Lin et al., 2014; Nehl, Wong, He, Huang, & Zheng, 2012; Wong et al., 2008, 2009, 2010; Yan et al., 2014, 2015).
Because MSM are hidden from the hetero-normative culture in many countries, including China, recruiting a sample representative of a larger MSM population is a challenging task. Empirical evidence suggests that use of different recruitment methodologies could result in under- or over-estimates of the health and psychosocial outcome(s) (Stall & Wiley, 1988). For instance, in Fortaleza, Brazil, respondent-driven sampling (RDS) yielded MSM sample with lower socioeconomic status than snowball or time-location sampling methods (Kendall et al., 2008). In China, Guo et al. (2011) found that samples of MSM in Beijing obtained from four recruitment methods yielded different estimates for variables ranging from socio-demographic characteristics to prevalence of syphilis. Likewise, Qi et al. (2015) reported that MSM recruited in various physical locations and online in 15 cities in China differed in HIV and syphilis prevalence. Given these recruitment methods are the most common used in HIV/STI-prevention research among MSM in China, understanding their impact on the resulting sample characteristics is of high methodological importance. Not only sample composition may influence study results, it may also have significant policy and funding implications. Moreover, dependence of sample characteristics on the recruitment methodology may affect reproducibility of research. In this regard, we aim to investigate if samples with similar behavioral and psychosocial profiles can be reproduced by using different recruitment methods – namely, RDS, community popular opinion leaders (CPOL), and venue-based sampling (VBS) in Shanghai, China. In particular, we want to assess differences in self-reported demographics, psychosocial variables, substance use, and sexual risk behaviors across three samples.
Methods
Study sites and sampling methods
The “Shanghai’s Men Study” was conducted in Shanghai, one of the largest cities in China with a population of more than 23 million, 39% of which is comprised by internal Chinese migrants (World Population Review, 2016). We collected data from N = 1352 Chinese MSM (n = 721) and money boys (n = 631) recruited via three approaches – (1) RDS, (2) CPOL, and (3) VBS in 2008–2012. All participants were recruited voluntarily by networking within the MSM and money boy (men who sell sex to men) communities at various venues frequented by MSM and money boys in all 17 districts of Shanghai. For the RDS recruitment (Heckathorn, 1997, 2002), study staff initially recruited eight seeds: four MSM who were not money boys (two gay-identified and two non-gay-identified) and four money boys (two gay-identified and two non-gay-identified). Each seed recruited up to three peers, who then completed surveys and received three recruitment coupons to distribute to their peers. Coupons were used to track recruitment, affirm relationships, and prevent recruitment overlap. Those who recruited participants in the RDS method received approximately US$8 per each successful referral. The CPOL recruitment entailed the nomination of 40 CPOLs from different segments of the money boy and MSM populations by a local non-governmental organization (NGO). Of the CPOLs, 20 were money boys and 20 were general MSM, and each was trained on how to approach, and recruit a potential participant. Each CPOL was asked to recruit 10–15 money boys or general MSM. If interested, the recruited participant would be contacted by study staff and would report to the NGO office to determine eligibility and privately complete the survey. Last, VBS was conducted at each of the three following venues: (1) a variety of Internet applications, such as “QQ” which is a short messaging service, and JACKD and GRINDR, which are smart-phone applications, (2) bathhouses, and (3) bars. Fliers were posted at bathhouses and bars, and participants could call a hotline to learn more of the study. Additionally, with the permission of venue owners/managers, the study staff established “hang out” time to network with patrons and pre-screen potential participants. Interested and eligible individuals gave informed consent and completed the survey in the NGO office.
Participants
Inclusion criteria were being male, 18 years or older, able to give consent in Mandarin, reporting sex with another man in the past year (oral, anal, or both), and self-identifying as a money boy or general MSM. All participants provided informed consent in Mandarin Chinese and received $40US in compensation for their time and effort.
Data collection
All participants completed an anonymous pencil-and-paper survey (30–45 minutes long) consisted of (1) socio-demographic characteristics, (2) psychosocial variables (e.g., intimate partner violence [IPV], depression), and (3) HIV-related practices and behaviors (e.g., unprotected anal sex, substance use). The survey content and method of administration were identical for all three samples.
Measures
Demographic characteristics included date of birth, location of legal residency (hukou; Shanghai vs. other), ethnicity (Han vs. non-Han), education level, marital status, monthly income (~US$1 = 6.3 RMB at the conclusion of the study), sexual orientation (gay, bisexual, heterosexual, other) and disclosure (openly or closeted gay or bisexual [i.e., those who did not disclose their non-heterosexual orientation to families and friends]), and age at first sex with women and men.
Sexual behaviors were assessed by asking about ever having condomless sex with a man or a woman and anal sex with any partner; number of male and female partners in the past 30 days and in the lifetime. We also asked participants about any illicit drug use over the course of their lifetime.
To assess depressive symptoms, the short-form version of the Center for Epidemiologic Studies Depression Scale (CES-D-12) was used (Radloff, 1977). CES-D-12 scores range from 0 to 36 with 11 and 20 being cutoff points for somewhat elevated and very elevated levels of depressive symptoms. The CES-D-12’s reliability was good for the total sample (Cronbach’s alpha = 0.88) and for each recruitment method sample (Cronbach’s alpha for RDS = 0.87, for CPOL = 0.90, and for VBS = 0.88).
In order to evaluate a participant’s history with male-on-male IPV, we asked a series of questions about different types of physical, emotional, social, or financial abuse received from boyfriends in the past five years and the number of boyfriends that had inflicted a particular type of violence.
Statistical analysis
This study assessed the effect of recruitment method on (1) sample demographics, (2) sexual risk behaviors, (3) substance use, and (4) psychosocial variables among MSM and money boys in Shanghai, China. First, descriptive statistics assessed distribution of each variable in the total sample and for each recruitment method. Second, one-way ANOVAs with recruitment method (RDS, CPOL, and VBS) as the between-subject factor for continuous variables and Chi-square tests for categorical variables were used to compare data from different recruitment methods. Significant differences were established at values of α = .05. Data from participants (n = 17) who reported participation in previous waves of data collection were excluded from the analysis.
Results
Missing data comprised less than 1.1% of observations (n < 15) for any given variable. The average age of the total sample (n = 1335) was 29.5 (standard deviation [SD] = 9.6) years. Across the RDS (n = 404), CPOL (n = 385), and VBS (n = 546) participants, average age for each sample was significantly different with the CPOL sample being on average the youngest and the VBS sample the oldest one (p < .001; see Table 1). On average, participants had their first sexual experience with either a man or woman at 18.3 (SD = 4.0) years (p < .001) with CPOL participants having their sexual debut at the youngest age (p < .001; Table 1).
Table 1.
Comparison of sample demographics by recruitment method.
| Recruitment type | |||||
|---|---|---|---|---|---|
| Characteristic | RDS (n = 404) | CPOL (n = 385) | VBS (n = 546) | Total sample N = 1335 | Sig. F or X2, p |
| Mean (SD) | |||||
| Age (years) (missing – 1) | 29.7 (10.4) | 27.7 (7.9) | 30.8 (9.9) | 29.5 (9.6) | 12.75, <.001 |
| Age at first sex (years) | |||||
| First sex with men (missing – 10) | 19.9 (6.1) | 18.9(5.5) | 21.0(6.1) | 20.0 (6.0) | 13.78, <.001 |
| First sex with women (n for those reporting sex with women = 904, missing – 9) | 20.4 (4.5) | 19.5 (3.9) | 21.1 (4.4) | 20.4 (4.3) | 10.89, <.001 |
| First sex (any sex) (missing – 10) | 18.1 (4.0) | 17.6 (3.9) | 19.1 (3.8) | 18.3 (4.0) | 17.91, <.001 |
| n (%) | |||||
| Monthly income less than 3000 RMB (missing – 3) | 229 (56.7) | 137(35.6) | 183 (33.5) | 549 (41.1) | 58.56, <.001 |
| Han ethnicity (missing – 4) | 386 (95.5) | 365 (94.8) | 517 (94.7) | 1,303 (96.4) | 1.00, .606 |
| Shanghai resident (missing – 2) | 82 (20.3) | 93 (24.2) | 129 (23.6) | 304 (22.8) | 2.12, .345 |
| Level of education (missing – 2) | |||||
| Middle school or less | 148 (36.6) | 112 (29.1) | 157 (28.8) | 417 (31.2) | 17.02, .002 |
| High school or equivalent | 161 (39.9) | 141 (36.6) | 205 (37.6) | 507 (38.2) | |
| Currently married (missing – 7) | 59 (14.6) | 44 (11.4) | 115 (21.1) | 218 (16.3) | 15.84, <.001 |
| Sexual orientation (missing – 0) | |||||
| Gay | 229 (56.7) | 273 (70.9) | 349 (63.9) | 851 (63.8) | 36.19, <.001 |
| Bisexual | 141 (34.9) | 77 (20.0) | 177 (32.4) | 395 (29.6) | |
| Being openly gay or bisexual (n for all gay or bisexual participants = 1246) | 49 (12.1) | 29 (7.5) | 416 (7.5) | 119 (8.9) | 8.36, .015 |
Note: % includes missing responses. RDS, respondent-driven sampling; CPOL, community popular opinion leaders; VBS, venue-based sampling. p-values equal to or below the significance level of .05 are presented in bold font.
The majority of participants were of the Han ethnicity (96.4%) and had no Shanghai legal residency status (hukou) (77.1%) with no significant difference across the recruitment methods. Almost a third of participants (31.2%) reported middle school education or less, 38.2% had a high school or equivalent education, and 30.6% had education equal to or above college level. The RDS sample had the highest share of men (76.5%) with no college education (p = .002). Monthly income distribution showed that the RDS sample had the highest percentage (56.7%) of men making less than 3000 RMB/month as compared to the CPOL (35.6%) or VBS (33.5%) samples (p < .001; Table 1).
A majority (93.4%) of the participants reported being gay or bisexual, and 8.9% of them were openly gay or bisexual. The CPOL sample had the highest share of gay participants (70.9%, p < .001) while the highest proportion of openly gay or bisexual men was observed in the RDS sample (12.1%; p = .015). Most participants were unmarried (83.1%) at the moment of taking the survey, and the highest proportion of married men has been observed in the VBS sample (21.1%; p < .001).
The majority of the sample reported ever having condomless sex with men (85.5%), and we detected no significant difference across the recruitment methods (p = .525; see Table 2). CPOL participants have been more likely to report condomless anal sex (82.6%) than men in other samples (RDS – 76.2%, VBS – 74.9%; p = .009). Overall, a nearly 50–50 split existed among participants who have ever had condomless sex with a woman, but there was a significant difference across the recruitment methods (p < .001). Nearly all of RDS participants (93.3%) have ever had sex without a condom with a man and a woman, while significantly fewer CPOL (38.2%) and VBS (42.7%) participants have reported this behavior (p < .001; Table 2).
Table 2.
Comparison of sexual behaviors and drug use by recruitment method.
| Recruitment type | |||||
|---|---|---|---|---|---|
| Characteristic | RDS (n = 404) | CPOL (n = 385) | VBS (n = 546) | Total sample N = 1335 | Sig. X2, p |
| Sex without condom | n (%) | ||||
| Condomless sex with a man ever (missing – 2) | 341 (84.4) | 327 (84.9) | 474 (86.8) | 1,142 (85.5) | 1.29, .525 |
| Condomless anal sex ever (missing – 11) | 308 (76.2) | 318 (82.6) | 409 (74.9) | 1,035 (77.5) | 9.52, .009 |
| Condomless sex with a woman ever (missing – 13) | 241 (59.7) | 167 (43.4) | 268 (49.1) | 676 (50.6) | 23.60, <.001 |
| Condomless sex with both a man and a woman ever (missing – 4) | 377 (93.3) | 147 (38.2) | 233 (42.7) | 757 (56.7) | 316.04, <.001 |
| Number of sex partners | |||||
| Number of male partners in the past 30 days | |||||
| None | 40 (9.9) | 45 (11.7) | 52 (9.5) | 137 (10.3) | 37.37, <.001 |
| 1–3 | 199 (49.3) | 161 (41.8) | 303 (55.5) | 663 (49.7) | |
| 4–9 | 75 (18.6) | 60 (15.6) | 108 (19.8) | 243 (18.2) | |
| 10 and more | 90 (22.3) | 119 (30.9) | 83 (15.2) | 292 (21.9) | |
| Any female partners in the past 30 days (missing – 13) | 85 (21.0) | 40 (10.4) | 103 (18.9) | 229 (17.1) | 18.53, <.001 |
| Having both male and female partner in the past 30 days | 75 (18.6) | 37 (9.6) | 92 (16.9) | 204 (15.3) | 13.97, .001 |
| Number of male partners in the lifetime (missing – 5) | |||||
| 0–3 | 37 (9.2) | 23 (6.0) | 39 (7.1) | 99 (7.4) | 18.18, .001 |
| 4–9 | 44 (10.9) | 81 (21.0) | 103 (18.9) | 228 (17.1) | |
| 10 and more | 323 (80.0) | 279 (72.5) | 401 (73.4) | 1,003 (75.1) | |
| Number of female partners in the lifetime (missing – 14) | |||||
| None | 109 (27.0) | 176 (45.7) | 200 (36.6) | 485 (36.3) | 33.91, <.001 |
| 1–3 | 205 (50.7) | 149 (38.7) | 216 (39.6) | 570 (42.7) | |
| 4 and more | 84 (20.8) | 59 (15.3) | 123 (22.5) | 266 (19.9) | |
| Drug use (ever) | 69 (17.1) | 63 (16.4) | 132 (24.2) | 264 (19.8) | 11.34, .003 |
Note: % includes missing responses. RDS, respondent-driven sampling; CPOL, community popular opinion leaders; VBS, venue-based sampling. p-values equal to or below the significance level of .05 are presented in bold font.
The number of sex partners was also different across the samples (see Table 2). Thus, the CPOL sample had the highest proportion (30.9%) of participants reporting 10 and more male partners in the past 30 days (p < .001), while the RDS sample had the highest share of men reporting both male and female sex partners in the past 30 days (18.6%, p < .001), as well as 10 and more male partners in the lifetime (80.0%; p = .001).
Overall, 19.8% of the sample had drug use history with significantly more MSM (24.2%) recruited via VBS reporting drug use than men in other samples (17.1% of RDS, 16.4% of CPOL; p = .003; Table 2).
RDS participants averaged the highest depression score of 10.5 (SD = 6.5), while the VBS sample had the lowest average score of 9.1 (SD = 6.7, p = .005) and fewer participants with somewhat elevated or very elevated depression symptoms (32.4%, p = .029; see Table 3)
Table 3.
Prevalence of depression and IPV stratified by recruitment method.
| Recruitment type | |||||
|---|---|---|---|---|---|
| Characteristic | RDS (n = 404) | CPOL (n = 385) | VBS (n = 546) | Total sample N = 1335 | F or X2, p |
| Depression | n (%) | ||||
| Minimal depressive symptoms | 235 (58.2) | 229 (59.5) | 369 (67.6) | 833 (62.4) | 10.9, .029 |
| Somewhat elevated depressive symptoms | 133 (32.9) | 123 (32.0) | 141 (25.8) | 397 (29.7) | |
| Very elevated depressive symptoms | 36 (8.9) | 33 (8.6) | 36 (6.6) | 105 (7.9) | |
| Overall CES-D sum score (μ, σ) | 10.5 (6.5) | 10.1 (7.1) | 9.1 (6.7) | 9.8 (6.8) | 5.29, .005 |
| Exposure to IPV | |||||
| Any exposure to a specific form of IPVa | |||||
| They threatened to stop helping you with money or housing (missing – 5) | 44 (10.9) | 25 (6.5) | 37 (6.8) | 106 (7.9) | 6.97, .031 |
| Damaged or destroyed your property (missing – 5) | 55 (13.6) | 20 (5.2) | 67 (12.3) | 142 (10.6) | 17.25, <.001 |
| Threatened to tell others about your sexuality (missing – 6) | 36 (8.9) | 27 (7.0) | 75 (13.7) | 138 (10.3) | 12.11, .002 |
| Verbally threatened to harm you physically or emotionally (missing – 6) | 103 (25.5) | 72 (18.7) | 144 (26.4) | 319 (23.9) | 8.06, .018 |
| They hit you or threw something at you (missing – 5) | 59 (14.6) | 48 (12.5) | 70 (12.8) | 177 (13.3) | .95, .621 |
| Forced you to have sex when you didn’t want to (missing – 5) | 23 (5.7) | 47 (12.2) | 25 (4.6) | 95 (7.12) | 21.78, <.001 |
| Verbally threatened to physically harm someone you care for (missing – 6) | 100 (24.8) | 72 (18.7) | 143 (26.2) | 315 (23.6) | 7.37, .025 |
| Exposure to several IPV formsb (missing – 4) | |||||
| No IPV exposure | 196 (48.5) | 241 (62.6) | 276 (50.6) | 713 (53.4) | 18.48, .001 |
| 1–2 forms | 146 (36.1) | 104 (27.0) | 187 (34.3) | 437 (32.7) | |
| More than 2 forms | 58 (14.4) | 40 (10.4) | 83 (15.2) | 181 (13.6) | |
Note: % includes missing responses. RDS – respondent-driven sampling, CPOL – community popular opinion leaders, VBS – venue-based sampling. p-values equal to or below the significance level of .05 are presented in bold font.
n and % of participants reporting at least one boyfriend who perpetrated specific form of IPV on them in the past 5 years.
The number of various forms of IPV perpetrated by boyfriend(s) against a participant in the past 5 years.
Across three samples, CPOL had significantly lower share (37.4%) of those reporting abuse from male partners than other samples (p = .001). Proportion of participants exposed to specific forms of IPV has been significantly different almost for each form of IPV, though no particular pattern can be ascertained for any sample (see Table 3).
Discussion
The goal of this study was to compare estimates of demographic characteristics, sexual behaviors, drug use, and psychosocial variables (depression and IPV) across three samples of MSM and money boys recruited via different methods in Shanghai, China.
This study found that different recruitment methods provided samples with distinct socioeconomic and risk profiles. In particular, as compared to other two samples, participants from the RDS sample have been more likely to have lower education and income level and to be openly gay or bisexual. RDS participants have also been more likely to report unprotected sex with a man and a woman, more than 10 male sex partners over the lifetime, having sex with both men and women, and have higher depression score. CPOL-recruited participants on average have been younger and have had their sexual debut earlier than MSM from two other samples. They have also been more likely to report condomless anal sex and more than 10 male sex partners in the past 30 days and less likely to have female sex partners and violent boyfriends. Finally, participants recruited via VBS on average have been older, more likely to be married and less likely to report more than 10 male sex partners in the past 30 days. VBS participants have also been more likely to have a history of drug use and at the same time less likely to report depression symptoms than participants recruited by other methods. No recruitment method delivered a sample with uniformly higher prevalence of all HIV risk behaviors. Notably, there was no significant difference in prevalence of unprotected sex with a man over the lifetime across the samples in our study.
These differences in characteristics of samples correspond with the findings by Guo et al. (2011) for MSM in Beijing. Guo et al. also reported statistically significant differences in mean age, sexual debut age, education level, and drug use across samples obtained via network sampling (comparable to our RDS recruitment), peer outreach (analogous to CPOL in our study), and venue-based sampling (similar to our VBS). Furthermore, comparison of estimates obtained via comparable methods in both studies shows that Guo et al. findings often follow patterns observed for our samples. For example, both CPOL and peer outreach methods yielded the youngest samples, and both venue and VBS methods resulted in samples with the largest reported prevalence of lifetime drug use. Monthly income and age of sexual debut patterns also coincided for the comparable samples of both studies. At the same time, education level was the lowest in the venue sample of Guo et al. while in our study the highest proportion of participants with middle school or lower education level was found in the RDS sample.
Some of the differences in the samples may be explained by the specifics of networks reached within each recruitment method. For example, more prevalent drug use in the VBS sample (also observed by Guo et al.) can be due to higher likelihood of MSM’s exposure to drugs in bars and bathhouses. The reported differences across the methods may be due to bias introduced by each method rather than represent actual variation in characteristics of population segments.
Our findings suggest that no single recruitment method was more effective in reaching the most at-risk sub-group of MSM than others. Presumably, each recruitment method tapped into different segments of MSM population with specific risk profiles. Prevalence of health-seeking behaviors may also vary in the samples obtained from different recruitment methods. For example, using data from the same Shanghai’s Men Study, Huang et al. (2012) found that HIV testing was more prevalent among money boys recruited via Internet-based seeds than among those recruited via venue-based seeds. Therefore, we support the argument made by Guo et al. (2011) that employing a combination of recruitment methods should be used among MSM research to generate a diverse sample of MSM with different risk profiles. Furthermore, we concur with the recommendations based on findings from China (Guo et al., 2011; Huang et al., 2012) and other countries (see, e.g., Grov, 2012) that different recruitment methods or channels of communication may be more preferable in reaching the target population depending on the specific risk or protective factor (e.g., drug use, depression, sexual risk, or HIV-testing behavior).
The study has certain limitations. Recruitment strategies in this study were not implemented simultaneously and took place in successive rounds over several years, so differences in the samples may be due to history bias. Second, findings from this study in Shanghai may have limited generalizability to other geographical areas of China. Third, all data were self-reported, so social desirability and recall biases may be present in these results. Finally, there was no standard recruitment method or representative sample of Shanghai MSM to compare our findings against it.
Future exploration of the impact of recruitment methods should involve comparisons of studies with similar participant selection criteria and a wide range of comparable socio-demographic and risk factor variables. Additionally, qualitative inquiry needs to complement quantitative research, for example, ethnographic comparison of study participants and those who chose not to participate may help identify potential sources of selection bias in the network-based recruitment methods (Heimer, 2005).
Conclusion
MSM in China have the highest prevalence of HIV and other STIs in comparison to other populations, and experience co-occurring psychological and social conditions that further contribute to the excess burden of disease among MSM. Utilizing an appropriate recruitment methodology is crucial in capturing a sample of MSM that accurately reflects the prevalence of STIs and co-occurring psychosocial health problems. We have demonstrated that among general MSM and money boys in Shanghai various recruitment methods may yield samples with varying socio-demographic characteristics, sexual risk behaviors, and psychosocial risk factors such as depression and IPV. Our findings suggest that each recruitment method may reach a sub-group of MSM with specific risk profile and multiple recruitment methods are needed to obtain more representative sample of MSM.
Funding
The study was supported by a grant from the Eunice Shriver National Institute on Child Health and Human Development (R01HD056956) to Frank Y. Wong. All opinions expressed are those of the authors. Preparation of this study was supported in part by the Emory Center for AIDS Research (P30 AI050409) to both third and last authors.
Footnotes
Disclosure statement
No potential conflict of interest was reported by the authors.
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