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Cyprian Wejnert

Bio: Cyprian Wejnert is an academic researcher from Centers for Disease Control and Prevention. The author has contributed to research in topics: Men who have sex with men & Population. The author has an hindex of 26, co-authored 73 publications receiving 2176 citations. Previous affiliations of Cyprian Wejnert include Oak Ridge Institute for Science and Education & Cornell University.


Papers
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Journal ArticleDOI
19 May 2014-PLOS ONE
TL;DR: Estimates of the number of PWID and disease rates among PWID are important for program planning and addressing health inequities and rates of HIV among PWIDs by gender-, age-, and race/ethnicity are calculated.
Abstract: Background: Injection drug use provides an efficient mechanism for transmitting bloodborne viruses, including human immunodeficiency virus (HIV) and hepatitis C virus (HCV). Effective targeting of resources for prevention of HIV and HCV infection among persons who inject drugs (PWID) is based on knowledge of the population size and disparity in disease burden among PWID. This study estimated the number of PWID in the United States to calculate rates of HIV and HCV infection. Methods: We conducted meta-analysis using data from 4 national probability surveys that measured lifetime (3 surveys) or past-year (3 surveys) injection drug use to estimate the proportion of the United States population that has injected drugs. We then applied these proportions to census data to produce population size estimates. To estimate the disease burden among PWID by calculating rates of disease we used lifetime population size estimates of PWID as denominators and estimates of HIV and HCV infection from national HIV surveillance and survey data, respectively, as numerators. We calculated rates of HIV among PWID by gender-, age-, and race/ethnicity. Results: Lifetime PWID comprised 2.6% (95% confidence interval: 1.8%–3.3%) of the U.S. population aged 13 years or older, representing approximately 6,612,488 PWID (range: 4,583,188–8,641,788) in 2011. The population estimate of past-year PWID was 0.30% (95% confidence interval: 0.19 %–0.41%) or 774,434 PWID (range: 494,605–1,054,263). Among lifetime PWID, the 2011 HIV diagnosis rate was 55 per 100,000 PWID; the rate of persons living with a diagnosis of HIV infection in 2010 was 2,147 per 100,000 PWID; and the 2011 HCV infection rate was 43,126 per 100,000 PWID. Conclusion: Estimates of the number of PWID and disease rates among PWID are important for program planning and addressing health inequities.

213 citations

Journal ArticleDOI
TL;DR: Web-based RDS (WebRDS) is found to be highly efficient and effective and methods for testing the validity of assumptions required by RDS estimation are presented.
Abstract: This study tests the feasibility, effectiveness, and efficiency of respondent-driven sampling (RDS) as a Web-based sampling method. Web-based RDS (WebRDS) is found to be highly efficient and effective. The online nature of WebRDS allows referral chains to progress very quickly, such that studies with large samples can be expected to proceed up to 20 times faster than with traditional sampling methods. Additionally, the unhidden nature of the study population allows comparison of RDS estimators to institutional data. Results indicate that RDS estimates are reasonable but not precise. This is likely due to bias associated with the random recruitment assumption and small sample size of the study. Finally, this article presents methods for testing the validity of assumptions required by RDS estimation.

209 citations

Journal ArticleDOI
TL;DR: Testing three factors related to RDS estimation against institutional data using two Web RDS samples of university undergraduates suggests the standard degree measure currently employed in most RDS studies is among the best-performing degree measures.
Abstract: This paper, which is the first large scale application of Respondent-Driven Sampling (RDS) to non-hidden populations, tests three factors related to RDS estimation against institutional data using two WebRDS samples of university undergraduates. First, two methods of calculating RDS point estimates are compared. RDS estimates calculated using both methods coincide closely, but variance estimation, especially for small groups, is problematic for both methods. In one method, the bootstrap algorithm used to generate confidence intervals is found to underestimate variance. In the other method, where analytical variance estimation is possible, confidence intervals tend to overestimate variance. Second, RDS estimates are found to be robust against varying measures of individual degree. Results suggest the standard degree measure currently employed in most RDS studies is among the best performing degree measures. Finally, RDS is found to be robust against the inclusion of out-of-equilibrium data. The results show that valid point estimates can be generated with RDS analysis using real data, however further research is needed to improve variance estimation techniques.

185 citations

Journal ArticleDOI
31 Jul 2016-AIDS
TL;DR: The data suggest that condom use decreased among MSM and that the trends are not explained by serosorting or ART, suggesting that the benefits of ART in reducing transmission of HIV are not undermined.
Abstract: Objective: Evaluate changes in condomless anal sex at last sex among men who have sex with men (MSM) and assess if these changes are associated with the adoption of serosorting and biomedical prevention. Design: The National HIV Behavioral Surveillance is a crosssectional survey done in up to 21 cities in 2005, 2008, 2011 and 2014. Methods: MSM were recruited through venue-based sampling. Among men reporting at least one male partner, we evaluated changes in condomless anal sex at last sex with a partner with (1) HIV-concordant (proxy for serosorting) or (2) HIV-discordant (discordant/unknown) status. We hypothesized that if concordant condomless sex was increasing while discordant was stable/declining, the increases could be driven by more men attempting to serosort. We used generalized estimating equations assuming a Poisson distribution and robust variance estimator to explore whether temporal changes in the outcomes varied by selected characteristics. We also assessed changes in condomless anal sex by antiretroviral therapy (ART) use among HIV-positive MSM. Results: Among 5371 HIV-positive MSM, there were increases in concordant (19% in 2005 to 25% in 2014, P < 0.001) and discordant condomless sex (15 to 19%, P < 0.001). The increases were not different by ART use. Among 30 547 HIV-negative MSM, concordant (21 to 27%, P < 0.001) and discordant condomless sex (8 to 13%, P < 0.001) increased. Conclusion: Our data suggest that condom use decreased among MSM and that the trends are not explained by serosorting or ART. Promotion of condoms and increased access to preexposure prophylaxis are vital to ensure that the benefits of ART in reducing transmission of HIV are not undermined.

124 citations

Journal Article
TL;DR: Additional efforts are needed to reduce risk behaviors and increase access to HIV testing, drug treatment, and other HIV prevention programs to further reduce HIV infections among PWID.
Abstract: In the United States, an estimated 7% of new diagnoses of human immunodeficiency virus (HIV) infection in 2012 were attributed to injection drug use, and an additional 3% to male-to-male sexual contact and injection drug use. To monitor HIV prevalence and behaviors associated with HIV risk and prevention among persons who inject drugs (PWID), CDC's National HIV Behavioral Surveillance (NHBS) system conducts interviews and HIV testing in selected cities. This report summarizes HIV prevalence and behaviors among PWID interviewed and tested in 20 cities in 2012. Of the 10,002 PWID tested, 11% had a positive HIV test result. Among 9,425 PWID included in the behavioral analysis, 30% receptively shared syringes, 70% had vaginal sex without a condom, 25% had heterosexual anal sex without a condom, and 5% of males had male-to-male sexual contact without a condom in the previous 12 months. Fifty-one percent of PWID included in the behavioral analysis had been tested for HIV, 25% participated in an HIV behavioral intervention, and 39% participated in substance abuse treatment in the previous 12 months. Additional efforts are needed to reduce risk behaviors and increase access to HIV testing, drug treatment, and other HIV prevention programs to further reduce HIV infections among PWID.

117 citations


Cited by
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Proceedings ArticleDOI
22 Jan 2006
TL;DR: Some of the major results in random graphs and some of the more challenging open problems are reviewed, including those related to the WWW.
Abstract: We will review some of the major results in random graphs and some of the more challenging open problems. We will cover algorithmic and structural questions. We will touch on newer models, including those related to the WWW.

7,116 citations

Journal ArticleDOI
22 Feb 1995-JAMA
TL;DR: This survey of sexual practices in the United States has been combed by the media for items of interest to the public: monogamous sex is much more widespread in this country than has been thought.
Abstract: This survey of sexual practices in the United States has been combed by the media for items of interest to the public: monogamous sex is much more widespread in this country than has been thought; infidelity is less frequent than presumed; vaginal intercourse is the defining experience of heterosexual behavior; watching one's partner undress is stimulating to many people; married couples have more sex than single people (unmarried, cohabiting couples have the most sex of all); the majority of couples experience sex twice a week to several times a month; 2.8% of men identify themselves as homosexual and 1.4% of women do so, but a higher percentage of people consider a same-gender experience to have some appeal; 75% of men always experience orgasm compared with 28.6% of women, but more nearly equal numbers of men and women declare themselves satisfied with their sexual experiences. The book is, in fact, a

1,810 citations

Journal ArticleDOI
TL;DR: The findings suggest that transgender women are a very high burden population for HIV and are in urgent need of prevention, treatment, and care services.
Abstract: Summary Background Previous systematic reviews have identified a high prevalence of HIV infection in transgender women in the USA and in those who sell sex (compared with both female and male sex workers). However, little is known about the burden of HIV infection in transgender women worldwide. We aimed to better assess the relative HIV burden in all transgender women worldwide. Methods We did a systematic review and meta-analysis of studies that assessed HIV infection burdens in transgender women that were published between Jan 1, 2000, and Nov 30, 2011. Meta-analysis was completed with the Mantel-Haenszel method, and random-effects modelling was used to compare HIV burdens in transgender women with that in adults in the countries for which data were available. Findings Data were only available for countries with male-predominant HIV epidemics, which included the USA, six Asia-Pacific countries, five in Latin America, and three in Europe. The pooled HIV prevalence was 19·1% (95% CI 17·4–20·7) in 11 066 transgender women worldwide. In 7197 transgender women sampled in ten low-income and middle-income countries, HIV prevalence was 17·7% (95% CI 15·6–19·8). In 3869 transgender women sampled in five high-income countries, HIV prevalence was 21·6% (95% CI 18·8–24·3). The odds ratio for being infected with HIV in transgender women compared with all adults of reproductive age across the 15 countries was 48·8 (95% CI 21·2–76·3) and did not differ for those in low-income and middle-income countries compared with those in high-income countries. Interpretation Our findings suggest that transgender women are a very high burden population for HIV and are in urgent need of prevention, treatment, and care services. The meta-analysis showed remarkable consistency and severity of the HIV disease burden among transgender women. Funding Center for AIDS Research at Johns Hopkins and the Center for Public Health and Human Rights at the JHU Bloomberg School of Public Health.

1,142 citations

Journal ArticleDOI
TL;DR: In his seminal book, Shewhart (1931) makes no demand on the distribution of the characteristic to be plotted on a control chart, so how can the idea that normality is, if not required, at least highly desirable be explained?
Abstract: In his seminal book, Shewhart (1931) makes no demand on the distribution of the characteristic to be plotted on a control chart. How then can we explain the idea that normality is, if not required, at least highly desirable? I believe that it has come about through the many statistical studies of control-chart behavior. If one is to study how a control chart behaves, it is necessary to relate it to some distribution. The obvious choice is the normal distribution because of its ubiquity as a satisfactory model. This is bolstered by the existence of the Central Limit Theorem.

896 citations

Journal ArticleDOI
TL;DR: This comment summarizes the development of the RDS method, distinguishing among seven forms of the estimator, and offers a clarification of a related set of issues.
Abstract: Leo Goodman (2011) provided a useful service with his clarification of the differences among snowball sampling as originally introduced by Coleman (1958–1959) and Goodman (1961) as a means for studying the structure of social networks; snowball sampling as a convenience method for studying hard-to-reach populations (Biernacki and Waldorf 1981); and respondent-driven sampling (RDS), a sampling method with good estimability for studying hard-to-reach populations (Heckathorn 1997, 2002, 2007; Salganik and Heckathorn 2004; Volz and Heckathorn 2008). This comment offers a clarification of a related set of issues. One is confusion between the latter form of snowball sampling, and RDS. A second is confusion resulting from multiple forms of the RDS estimator that derives from the incremental manner in which the method was developed. This comment summarizes the development of the method, distinguishing among seven forms of the estimator.

652 citations