Publications by authors named "Justin Lessler"

Background: The prevention and control of infectious disease outbreaks in carceral settings face unique challenges. Transmission modeling is a powerful tool for understanding and addressing these challenges, but reviews of modeling work in this context pre-date the proliferation of outbreaks in jails and prisons during the SARS-CoV-2 pandemic. We conducted a systematic review of studies using transmission models of respiratory infections in carceral settings before and during the pandemic.

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Most infections with pandemic are thought to result in subclinical disease and are not captured by surveillance. Previous estimates of the ratio of infections to clinical cases have varied widely (2 to 100 infections per case). Understanding cholera epidemiology and immunity relies on the ability to translate between numbers of clinical cases and the underlying number of infections in the population.

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Humans experience many influenza infections over their lives, resulting in complex and varied immunological histories. Although experimental and quantitative analyses have improved our understanding of the immunological processes defining an individual's antibody repertoire, how these within-host processes are linked to population-level influenza epidemiology in humans remains unclear. Here, we used a multilevel mathematical model to jointly infer antibody dynamics and individual-level lifetime influenza A/H3N2 infection histories for 1,130 individuals in Guangzhou, China, using 67,683 haemagglutination inhibition (HI) assay measurements against 20 A/H3N2 strains from repeat serum samples collected between 2009 and 2015.

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Article Synopsis
  • The accuracy of pathogen sequence data analysis relies heavily on the number and type of sequences included in the sample, impacting the conclusions drawn from phylogenetic studies.
  • There is a lack of clear guidance on designing effective studies for phylogenetic inference, specifically regarding how to determine which individuals are more likely to spread pathogens.
  • The study introduces a new estimator for measuring differential pathogen transmission among individuals, provides sample size calculations, and offers an R package called phylosamp for practical implementation and validation of the method.
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  • The initial phase of the 2022 mpox outbreak saw a rapid increase in countries reporting imported cases, but the rate of new cases slowed significantly by the end of the year.
  • Researchers developed a mathematical model that used sexual networks and global travel data to analyze patterns of mpox importation and potential future spread.
  • The study found that the decrease in importation risk may be linked to increased immunity in high-risk groups, but some countries still pose a risk for future global outbreaks, emphasizing the need for equitable access to resources to prevent resurgence.
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The COVID-19 pandemic has highlighted the need to upgrade systems for infectious disease surveillance and forecasting and modeling of the spread of infection, both of which inform evidence-based public health guidance and policies. Here, we discuss requirements for an effective surveillance system to support decision making during a pandemic, drawing on the lessons of COVID-19 in the U.S.

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  • Accurate forecasts improve public health responses to seasonal influenza, with 26 teams providing predictions for hospital admissions in 2021-22 and 2022-23.
  • Six out of 23 models performed better than the baseline in 2021-22, while 12 out of 18 models did so in 2022-23, with the FluSight ensemble being highly ranked in both seasons.
  • Despite its accuracy, the FluSight ensemble and other models struggled with longer forecast periods, especially during times of rapid change in influenza patterns.
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Across many fields, scenario modeling has become an important tool for exploring long-term projections and how they might depend on potential interventions and critical uncertainties, with relevance to both decision makers and scientists. In the past decade, and especially during the COVID-19 pandemic, the field of epidemiology has seen substantial growth in the use of scenario projections. Multiple scenarios are often projected at the same time, allowing important comparisons that can guide the choice of intervention, the prioritization of research topics, or public communication.

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During the COVID-19 pandemic, forecasting COVID-19 trends to support planning and response was a priority for scientists and decision makers alike. In the United States, COVID-19 forecasting was coordinated by a large group of universities, companies, and government entities led by the Centers for Disease Control and Prevention and the US COVID-19 Forecast Hub (https://covid19forecasthub.org).

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  • COVID-19 is still a major public health issue in the U.S., with projected hospitalizations and deaths over the next two years varying based on assumptions about immune escape and vaccine recommendations.
  • Researchers used modeling to create six different scenarios combining levels of immune escape (20% and 50% per year) and CDC vaccination recommendations for different age groups.
  • In the worst-case scenario (high immune escape and no vaccination), COVID-19 could lead to over 2.1 million hospitalizations and around 209,000 deaths, while targeted vaccinations for seniors could significantly reduce these numbers.
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Despite ongoing containment and vaccination efforts, cholera remains prevalent in many countries in sub-Saharan Africa. Part of the difficulty in containing cholera comes from our lack of understanding of how it circulates throughout the region. To better characterize regional transmission, we generated and analyzed 118 genomes collected between 2007-2019 from five different countries in Southern and Eastern Africa.

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Humans experience many influenza infections over their lives, resulting in complex and varied immunological histories. Although experimental and quantitative analyses have improved our understanding of the immunological processes defining an individual's antibody repertoire, how these within-host processes are linked to population-level influenza epidemiology remains unclear. Here, we used a multi-level mathematical model to jointly infer antibody dynamics and individual-level lifetime influenza A/H3N2 infection histories for 1,130 individuals in Guangzhou, China, using 67,683 haemagglutination inhibition (HI) assay measurements against 20 A/H3N2 strains from repeat serum samples collected between 2009 and 2015.

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The COVID-19 pandemic led to an unprecedented demand for projections of disease burden and healthcare utilization under scenarios ranging from unmitigated spread to strict social distancing policies. In response, members of the Johns Hopkins Infectious Disease Dynamics Group developed flepiMoP (formerly called the COVID Scenario Modeling Pipeline), a comprehensive open-source software pipeline designed for creating and simulating compartmental models of infectious disease transmission and inferring parameters through these models. The framework has been used extensively to produce short-term forecasts and longer-term scenario projections of COVID-19 at the state and county level in the US, for COVID-19 in other countries at various geographic scales, and more recently for seasonal influenza.

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Throughout the COVID-19 pandemic, scenario modeling played a crucial role in shaping the decision-making process of public health policies. Unlike forecasts, scenario projections rely on specific assumptions about the future that consider different plausible states-of-the-world that may or may not be realized and that depend on policy interventions, unpredictable changes in the epidemic outlook, etc. As a consequence, long-term scenario projections require different evaluation criteria than the ones used for traditional short-term epidemic forecasts.

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Certain occupations have been associated with heightened risk of HIV acquisition and spread in sub-Saharan Africa, including female bar and restaurant work and male transportation work. However, data on changes in population prevalence of HIV infection and HIV incidence within occupations following mass scale-up of African HIV treatment and prevention programs is very limited. We evaluated prospective data collected between 1999 and 2016 from the Rakai Community Cohort Study, a longitudinal population-based study of 15- to 49-year-old persons in Uganda.

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Background: A global shortage of cholera vaccines has increased the use of single-dose regimens, rather than the standard two-dose regimen. There is sparse evidence on single-dose protection, particularly in children. In 2020, a mass vaccination campaign was conducted in Uvira, an endemic urban setting in eastern Democratic Republic of the Congo, resulting in largely single-dose coverage.

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Between December 2020 and April 2023, the COVID-19 Scenario Modeling Hub (SMH) generated operational multi-month projections of COVID-19 burden in the US to guide pandemic planning and decision-making in the context of high uncertainty. This effort was born out of an attempt to coordinate, synthesize and effectively use the unprecedented amount of predictive modeling that emerged throughout the COVID-19 pandemic. Here we describe the history of this massive collective research effort, the process of convening and maintaining an open modeling hub active over multiple years, and attempt to provide a blueprint for future efforts.

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Accurate forecasts can enable more effective public health responses during seasonal influenza epidemics. Forecasting teams were asked to provide national and jurisdiction-specific probabilistic predictions of weekly confirmed influenza hospital admissions for one through four weeks ahead for the 2021-22 and 2022-23 influenza seasons. Across both seasons, 26 teams submitted forecasts, with the submitting teams varying between seasons.

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Our ability to forecast epidemics far into the future is constrained by the many complexities of disease systems. Realistic longer-term projections may, however, be possible under well-defined scenarios that specify the future state of critical epidemic drivers. Since December 2020, the U.

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Most infections with pandemic Vibrio cholerae are thought to result in subclinical disease and are not captured by surveillance. Previous estimates of the ratio of infections to clinical cases have varied widely (2 to 100). Understanding cholera epidemiology and immunity relies on the ability to translate between numbers of clinical cases and the underlying number of infections in the population.

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Article Synopsis
  • COVID-19 is expected to continue causing significant hospitalizations and deaths in the U.S. from April 2023 to April 2025, with projections varying based on assumptions about immune escape and vaccination recommendations.
  • The study analyzes six scenarios based on different levels of immune escape (20% and 50% per year) and three vaccination strategies (no recommendation, vaccination for ages 65+, or vaccination for all eligible groups).
  • In the worst-case scenario, without vaccination and with high immune escape, projections estimate up to 2.1 million hospitalizations and 209,000 deaths, indicating a public health crisis that could surpass pre-pandemic influenza and pneumonia mortality rates.
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Across many fields, scenario modeling has become an important tool for exploring long-term projections and how they might depend on potential interventions and critical uncertainties, with relevance to both decision makers and scientists. In the past decade, and especially during the COVID-19 pandemic, the field of epidemiology has seen substantial growth in the use of scenario projections. Multiple scenarios are often projected at the same time, allowing important comparisons that can guide the choice of intervention, the prioritization of research topics, or public communication.

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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.

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Background: Cholera surveillance relies on clinical diagnosis of acute watery diarrhea. Suspected cholera case definitions have high sensitivity but low specificity, challenging our ability to characterize cholera burden and epidemiology. Our objective was to estimate the proportion of clinically suspected cholera that are true Vibrio cholerae infections and identify factors that explain variation in positivity.

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The academic, socioemotional, and health impacts of school policies throughout the COVID-19 pandemic have been a source of many questions that require accurate information about the extent of onsite schooling occurring. This article investigates school operational status datasets during the pandemic, comparing (1) self-report data collected nationally on the household level through a Facebook-based survey, (2) county-level school policy data, and (3) a school-level closure status dataset based on phone GPS tracking. The percentage of any onsite instruction within states and counties are compared across datasets from December 2020 to May 2021.

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