Synthesis estimators for transportability with positivity violations by a continuous covariate.

Studies intended to estimate the effect of a treatment, like randomized trials, may not be sampled from the desired target population. To correct for this discrepancy, estimates can be transported to the target population. Methods for transporting between populations are often premised on a positivity assumption, such that all relevant covariate patterns in one population are also present in the other.

Characterizing populations prioritized for PrEP in 19 African countries: a review of national guidance.

Introduction: While African countries have expanded access to HIV pre-exposure prophylaxis (PrEP) since 2015, regional targets for PrEP uptake remain unmet. Understanding which populations are prioritized for PrEP at the policy level is an important step in determining the scope of PrEP distribution across Africa and identifying gaps in programme implementation. We reviewed national guidance to characterize populations prioritized for PrEP in Africa.

The persistent pool of HIV-1-infected cells is formed episodically during untreated infection.

Previous studies have shown that the majority of long-lived cells harboring persistent HIV-1 proviral genomes originates from viruses circulating in the year prior to antiretroviral therapy (ART) initiation, but a smaller proportion originates from viruses circulating much earlier in untreated infection. These observations suggest that discrete biological factors influence the entry and persistence of viruses into the persistent proviral pool, and there may be periods earlier in untreated infection with increased seeding. Therefore, we examined the timing of formation of the long-lived pool of infected cells that persists during ART in seven women (after a median of 5.

EXPOSURE EFFECTS ON COUNT OUTCOMES WITH OBSERVATIONAL DATA, WITH APPLICATION TO INCARCERATED WOMEN.

Causal inference methods can be applied to estimate the effect of a point exposure or treatment on an outcome of interest using data from observational studies. For example, in the Women's Interagency HIV Study, it is of interest to understand the effects of incarceration on the number of sexual partners and the number of cigarettes smoked after incarceration. In settings like this where the outcome is a count, the estimand is often the causal mean ratio, i.

Empirical Sandwich Variance Estimator for Iterated Conditional Expectation g-Computation.

Iterated conditional expectation (ICE) g-computation is an estimation approach for addressing time-varying confounding for both longitudinal and time-to-event data. Unlike other g-computation implementations, ICE avoids the need to specify models for each time-varying covariate. For variance estimation, previous work has suggested the bootstrap.

Bridged Treatment Comparisons: an Illustrative Application in HIV Treatment.

Comparisons of treatments, interventions, or exposures are of central interest in epidemiology, but direct comparisons are not always possible due to practical or ethical reasons. Here, we detail a fusion approach to compare treatments across studies. The motivating example entails comparing the risk of the composite outcome of death, AIDS, or greater than a 50% CD4 cell count decline in people with HIV when assigned triple versus mono antiretroviral therapy, using data from the AIDS Clinical Trial Group (ACTG) 175 (mono versus dual therapy) and ACTG 320 (dual versus triple therapy).

Semiparametric g-computation for survival outcomes with time-fixed exposures: An illustration.

Purpose: Generalized (g-) computation is a useful tool for causal inference in epidemiology. However, in settings when the outcome is a survival time subject to right censoring, the standard pooled logistic regression approach to g-computation requires arbitrary discretization of time, parametric modeling of the baseline hazard function, and the need to expand one's dataset. We illustrate a semiparametric Breslow estimator for g-computation with time-fixed treatments and survival outcomes that is not subject to these limitations.

A novel use of HIV surveillance and court data to understand and improve care among a population of people with HIV experiencing criminal charges in North Carolina 2017-2020.

Objectives Objectives: To enumerate the population of people with HIV (PWH) with criminal charges and to estimate associations between charges and HIV outcomes.

Methods: We linked statewide North Carolina criminal court records to confidential HIV records (both 2017-2020) to identify a population of defendants with diagnosed HIV. We used generalized estimating equations to examine changes in viral suppression (outcome) pre-post criminal charges (exposure), adjusting for other demographic and legal system factors.

A Human Immunodeficiency Virus Type 1 Risk Assessment Tool for Women Aged 15-49 Years in African Countries: A Pooled Analysis Across 15 Nationally Representative Surveys.

Background: Women in Africa disproportionately acquire human immunodeficiency virus type 1 (HIV-1). Understanding which women are most likely to acquire HIV-1 can guide focused prevention with preexposure prophylaxis (PrEP). Our objective was to identify women at the highest risk of HIV-1 and estimate PrEP efficiency at different sensitivity levels.

Magnitude and Durability of the Antibody Response to mRNA-Based Vaccination Among SARS-CoV-2 Seronegative and Seropositive Health Care Personnel.

Few studies have described changes in SARS-CoV-2 antibody levels in response to infection and vaccination at frequent intervals and over extended follow-up periods. The purpose of this study was to assess changes in SARS-CoV-2-specific antibody responses among a prospective cohort of health care personnel over 18 months with up to 22 samples per person. Antibody levels and live virus neutralization were measured before and after mRNA-based vaccination with results stratified by (1) SARS-CoV-2 infection status prior to initial vaccination and (2) SARS-CoV-2 infection at any point during follow-up.

Higher-order evidence.

Higher-order evidence is evidence about evidence. Epidemiologic examples of higher-order evidence include the settings where the study data constitute first-order evidence and estimates of misclassification comprise the second-order evidence (e.g.

Estimating SARS-CoV-2 seroprevalence.

Governments and public health authorities use seroprevalence studies to guide responses to the COVID-19 pandemic. Seroprevalence surveys estimate the proportion of individuals who have detectable SARS-CoV-2 antibodies. However, serologic assays are prone to misclassification error, and non-probability sampling may induce selection bias.

Fusing trial data for treatment comparisons: Single vs multi-span bridging.

While randomized controlled trials (RCTs) are critical for establishing the efficacy of new therapies, there are limitations regarding what comparisons can be made directly from trial data. RCTs are limited to a small number of comparator arms and often compare a new therapeutic to a standard of care which has already proven efficacious. It is sometimes of interest to estimate the efficacy of the new therapy relative to a treatment that was not evaluated in the same trial, such as a placebo or an alternative therapy that was evaluated in a different trial.

HIV Prevention Among Men Who Have Sex With Men: Tenofovir Alafenamide Combination Preexposure Prophylaxis Versus Placebo.

Background: While noninferiority of tenofovir alafenamide and emtricitabine (TAF/FTC) as preexposure prophylaxis (PrEP) for the prevention of human immunodeficiency virus (HIV) has been shown, interest remains in its efficacy relative to placebo. We estimate the efficacy of TAF/FTC PrEP versus placebo for the prevention of HIV infection.

Methods: We used data from the DISCOVER and iPrEx trials to compare TAF/FTC to placebo.

Transportability Without Positivity: A Synthesis of Statistical and Simulation Modeling.

Studies designed to estimate the effect of an action in a randomized or observational setting often do not represent a random sample of the desired target population. Instead, estimates from that study can be transported to the target population. However, transportability methods generally rely on a positivity assumption, such that all relevant covariate patterns in the target population are also observed in the study sample.

Estimation of SARS-CoV-2 Seroprevalence in Central North Carolina: Accounting for Outcome Misclassification in Complex Sample Designs.

Background: Population-based seroprevalence studies are crucial to understand community transmission of COVID-19 and guide responses to the pandemic. Seroprevalence is typically measured from diagnostic tests with imperfect sensitivity and specificity. Failing to account for measurement error can lead to biased estimates of seroprevalence.

Comparison of capillary blood self-collection using the Tasso-SST device with venous phlebotomy for anti-SARS-CoV-2 antibody measurement.

Measuring seroprevalence over time is a valuable epidemiological tool for improving our understanding of COVID-19 immunity. Due to the large number of collections required for population surveillance as well as concerns about potential infection risk to the collectors, self-collection approaches are being increasingly pursued. To advance this methodology, we collected paired venous and capillary blood samples by routine phlebotomy and Tasso-SST device respectively from 26 participants and measured total immunoglobulin (Ig) and IgG antibodies to the SARS-CoV-2 receptor binding domain (RBD) by enzyme-linked immunosorbent assay (ELISA) on both specimens.

Pre-Heart Failure Longitudinal Change in a Hispanic/Latino Population-Based Study: Insights From the Echocardiographic Study of Latinos.

Background: Pre-heart failure (pre-HF) is an entity known to progress to symptomatic heart failure (HF).

Objectives: This study aimed to characterize pre-HF prevalence and incidence among Hispanics/Latinos.

Methods: The Echo-SOL (Echocardiographic Study of Latinos) assessed cardiac parameters on 1,643 Hispanics/Latinos at baseline and 4.

Sensitivity Analyses for Means or Proportions with Missing Outcome Data.

We describe an approach to sensitivity analysis introduced by Robins et al (1999), for the setting where the outcome is missing for some observations. This flexible approach focuses on the relationship between the outcomes and missingness, where data can be missing completely at random, missing at random given observed data, or missing not at random. We provide examples from HIV that include the sensitivity of the estimation of a mean and proportion under different missingness mechanisms.

Permethrin-treated baby wraps for the prevention of malaria in children: Protocol for a double-blind, randomized placebo-controlled controlled trial in western Uganda.

This article details the study protocol for a double-blind, randomized placebo-controlled trial to determine the effectiveness of permethrin-treated baby wraps to prevent Plasmodium falciparum malaria infection in children 6-24 months of age. Participating mother-infant dyads will be randomized to receive either a permethrin-treated or a sham-treated wrap, known locally as a "lesu." After a baseline home visit, during which time all participants will receive new long-lasting insecticidal nets, participants will attend scheduled clinic visits every two weeks for a period of 24 weeks.