Carol Y. Lin

Reduction in Human Papillomavirus (HPV) Prevalence Among Young Women Following HPV Vaccine Introduction in the United States, National Health and Nutrition Examination Surveys, 2003–2010

BACKGROUND Human papillomavirus (HPV) vaccination was introduced into the routine immunization schedule in the United States in late 2006 for females aged 11 or 12 years, with catch-up vaccination recommended for those aged 13-26 years. In 2010, 3-dose vaccine coverage was only 32% among 13-17 year-olds. Reduction in the prevalence of HPV types targeted by the quadrivalent vaccine (HPV-6, -11, -16, and -18) will be one of the first measures of vaccine impact. METHODS We analyzed HPV prevalence data from the vaccine era (2007-2010) and the prevaccine era (2003-2006) that were collected during National Health and Nutrition Examination Surveys. HPV prevalence was determined by the Linear Array HPV Assay in cervicovaginal swab samples from females aged 14-59 years; 4150 provided samples in 2003-2006, and 4253 provided samples in 2007-2010. RESULTS Among females aged 14-19 years, the vaccine-type HPV prevalence (HPV-6, -11, -16, or -18) decreased from 11.5% (95% confidence interval [CI], 9.2-14.4) in 2003-2006 to 5.1% (95% CI, 3.8-6.6) in 2007-2010, a decline of 56% (95% CI, 38-69). Among other age groups, the prevalence did not differ significantly between the 2 time periods (P > .05). The vaccine effectiveness of at least 1 dose was 82% (95% CI, 53-93). CONCLUSIONS Within 4 years of vaccine introduction, the vaccine-type HPV prevalence decreased among females aged 14-19 years despite low vaccine uptake. The estimated vaccine effectiveness was high.

High and persistent HIV seroincidence in men who have sex with men across 47 U.S. cities

Objective To provide HIV seroincidence data among men who have sex with men (MSM) in the United States and to identify predictive factors for seroconversion. Methods From 1998–2002, 4684 high-risk MSM, age 18–60 years, participated in a randomized, placebo-controlled HIV vaccine efficacy trial at 56 U.S. clinical trial sites. Demographics, behavioral data, and HIV status were assessed at baseline and 6 month intervals. Since no overall vaccine efficacy was detected, data were combined from both trial arms to calculate HIV incidence based on person-years (py) of follow-up. Predictors of seroconversion, adjusted hazards ratio (aHR), were evaluated using a Cox proportional hazard model with time-varying covariates. Results Overall, HIV incidence was 2.7/100 py and was relatively uniform across study sites and study years. HIV incidence was highest among young men and men reporting unprotected sex, recreational drug use, and a history of a sexually transmitted infection. Independent predictors of HIV seroconversion included: age 18–30 years (aHR = 2.4; 95% CI 1.4,4.0), having >10 partners (aHR = 2.4; 95% CI 1.7,3.3), having a known HIV-positive male sex partner (aHR = 1.6; 95% CI 1.2, 2.0), unprotected anal intercourse with HIV positive/unknown male partners (aHR = 1.7; 95% CI 1.3, 2.3), and amphetamine (aHR = 1.6; 95% CI 1.1, 2.1) and popper (aHR = 1.7; 95% CI 1.3, 2.2) use. Conclusions HIV seroincidence was high among MSM despite repeated HIV counseling and reported declines in sexual risk behaviors. Continuing development of new HIV prevention strategies and intensification of existing efforts will be necessary to reduce the rate of new HIV infections, especially among young men.

Factors Associated with Parent–Child Communication About HIV/AIDS in the United States and Kenya: A Cross-Cultural Comparison

This study explored parent–child communication about HIV/AIDS among two populations disproportionately affected by HIV. Similar computer-assisted surveys were completed by parents of pre-teens, including 1,115 African American parents of 9–12-year-old children in southeastern US and 403 parents of 10–12-year-old children in Nyanza Province, Kenya. Multivariate analyses identified factors associated with parental report of ever talking to their child about HIV/AIDS. Twenty-nine percent of US parents and 40% in Kenya had never talked to their pre-teen about HIV/AIDS. In both countries, communication was more likely if parents perceived their child to be ready to learn about sex topics, had gotten information to educate their child about sex, and had greater sexual communication responsiveness (skill, comfort, and confidence communicating about sexuality). Programs are needed that help parents assess children’s readiness to learn about sexual issues; access accurate information about adolescent sexual risks; and acquire the responsiveness needed to discuss sexual issues, including HIV/AIDS.

Improving global estimates of syphilis in pregnancy by diagnostic test type: a systematic review and meta-analysis.

“Probable active syphilis,” is defined as seroreactivity in both non‐treponemal and treponemal tests. A correction factor of 65%, namely the proportion of pregnant women reactive in one syphilis test type that were likely reactive in the second, was applied to reported syphilis seropositivity data reported to WHO for global estimates of syphilis during pregnancy.

Ready, Set, Go: African American Preadolescents’ Sexual Thoughts, Intentions, and Behaviors

Understanding of preadolescent sexuality is limited. To help fill this gap, we calculated frequencies, percentages, and confidence intervals for 1,096 preadolescents’ reports of sexual thoughts, intentions, and sexual behavior. Cochran-Armitage trend tests accounted for age effects. Findings show that 9-year-olds are readying for sexual activity, with sexual readiness increasing between ages of 9 and 12. Sexual thoughts increased with age (p < .001): 46% of 9-year-olds and 70% of 12-year-olds were ready to learn about sex, and 14% of 9-year-olds and 41% of 12-year-olds thought about having sex. Few 9-year-olds anticipated sexual debut, but this increased with age (p < .05): 25% of 12-year-olds were ready for sex, and 20% anticipated initiating sex within a year. Our results indicate that preadolescents are initiating dating relationships and anticipating intercourse, and some have engaged in risk behaviors. Thus preadolescence is a critical time to implement prevention programs.

Can clinical tests help monitor human papillomavirus vaccine impact

As immunization programs for human papillomavirus (HPV) are implemented more widely around the world, interest is increasing in measuring their impact. One early measurable impact of HPV vaccine is on the prevalence of specific HPV types in a population. In low‐resource settings, a potentially attractive strategy would be to monitor HPV prevalence using clinical cervical cancer screening test results to triage specimens for HPV typing. We assessed this approach in a nationally representative population of U.S. females aged 14–59 years. Using self‐collected cervico‐vaginal swab specimens from 4,150 women participating in the National Health and Nutrition Examination Survey during 2003–2006, we evaluated type‐specific HPV prevalence detected by the Roche linear array (LA) research test on all specimens, compared with type‐specific HPV prevalence detected by LA conducted only on specimens positive by the digene hybrid capture 2 (HC‐2) clinical test. We calculated weighted prevalence estimates and their 95% confidence intervals (CIs), and examined relative type‐specific HPV prevalence according to the two testing approaches. The population prevalence of oncogenic HPV vaccine types 16/18 was 6.2% (CI:5.4–7.1) by LA if all specimens were tested, and 2.4% (CI:1.9–3.0) if restricted to positive HC‐2. Relative prevalence of individual HPV types was similar for both approaches. Compared with typing all specimens, a triage approach would require testing fewer specimens, but a greater reduction in HPV prevalence or a larger group of specimens would be needed to detect vaccine impact. Further investigation is warranted to inform type‐specific HPV monitoring approaches around the world.

Evaluation of using composite HPV genotyping assay results to monitor human papillomavirus infection burden through simulation

BackgroundResearchers often group various HPV types into composite measures based on vaccine subtypes, oncogenic potential, or phylogenetic position. Composite prevalence estimates based on PCR genotyping assay results have been calculated to assess HPV infection burden and to monitor HPV vaccine effectiveness. While prevention and intervention strategies can be made based on these prevalence estimates, the discussion on how well these prevalence estimates measure the true underlying infection burdens is limited.MethodsA simulation study was conducted to evaluate accuracy of using composite genotyping assay results to monitor HPV infection burden. Data were generated based on mathematical algorithms with prespecified type-specific infection burdens, assay sensitivity, specificity, and correlations between various HPV types. Estimated-to-true prevalence rate ratios and percent reduction of vaccine types were calculated.ResultsWhen “true” underlying type-specific infection burdens were prespecified as the reported prevalence in U.S. and genotyping assay with sensitivity and specificity (0.95, 0.95) was used, estimated-to-true infection prevalence ratios were 2.35, 2.29, 2.18, and 1.46, for the composite measures with 2 high-risk vaccine, 4 vaccine, 14 high-risk and 37 HPV types, respectively. Estimated-to-true prevalence ratios increased when prespecified “true” underlying infection burdens or assay specificity declined. When prespecified “true” type-specific infections of HPV 6, 11, 16 and 18 were reduced by 50%, the composite prevalence estimate of 4 vaccine types only decreased by 17% which is much lower than 48% reduction in the prespecified “true” composite prevalence.ConclusionsComposite prevalence estimates calculated based on panels of genotyping assay results generally over-estimate the “true” underlying infection burdens and could under-estimate vaccine effectiveness. Analytical specificity of genotyping assay is as or more important than analytical sensitivity and should be considered in selecting assay to monitor HPV.

The likelihood approach for the comparison of medical diagnostic system with multiple binary tests

Detection (diagnosis) techniques play an important role in clinical medicine. Early detection of diseases could be life-saving, and the consequences of false-positives and false-negatives could be costly. Using multiple measurements strategy is a popular tool to increase diagnostic accuracy. In addition to the new diagnostic technology, recent advances in genomics, proteomics, and other areas have allowed some of these newly developed individual biomarkers measured by non-invasive and inexpensive procedures (e.g. samples from serum, urine or stool) to progress from basic discovery research to assay development. As more tests become commercially available, there is an increasing interest for clinicians to request combinations of various non-invasive and inexpensive tests to increase diagnostic accuracy. Using information regarding individual test sensitivities and specificities, we proposed a likelihood approach to combine individual test results and to approximate or estimate the combined sensitivities and specificities of various tests taking into account the conditional correlations to quantify system performance. To illustrate this approach, we considered an example using various combinations of diagnostic tests to detect bladder cancer.