Laura Matrajt

Laura Matrajt

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80
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Publications

Publications (80)
Article
Full-text available
Background Despite the development of safe and effective vaccines, effective treatments for COVID-19 disease are still urgently needed. Several antiviral drugs have shown to be effective in reducing progression of COVID-19 disease. Methods In the present work, we use an agent-based mathematical model to assess the potential population impact of th...
Article
Full-text available
Background: A global stockpile of oral cholera vaccine (OCV) was established in 2013 for use in outbreak response and are licensed as two-dose regimens. Vaccine availability, however, remains limited. Previous studies have found that a single dose of OCV may provide substantial protection against cholera. Methods: Using a mathematical model with...
Article
The rapid spread of highly transmissible SARS-CoV-2 variants combined with slowing pace of vaccination in Fall 2021 created uncertainty around the future trajectory of the epidemic in King County, Washington, USA. We analyzed the benefits of offering vaccination to children ages 5–11 and expanding the overall vaccination coverage using mathematical...
Preprint
Full-text available
Background: A global stockpile of oral cholera vaccine (OCV) was established in 2013 for use in outbreak response and are licensed as two-dose regimens. Vaccine availability, however, remains limited. Previous studies have found that a single dose of OCV may provide substantial protection against cholera. Methods: Using a mathematical model with tw...
Preprint
Full-text available
Despite the development of safe and effective vaccines, effective treatments for COVID-19 disease are still desperately needed. Several antiviral drugs have shown to be effective in reducing hospitalizations, and it is expected Despite the development of safe and effective vaccines, effective treatments for COVID-19 disease are still desperately ne...
Preprint
Full-text available
Background: The mass rollout of COVID vaccination in early 2021 allowed local and state authorities to relax mobility and social interaction regulations in spring 2021 including lifting all restrictions for vaccinated people and restoring in-person schooling. However, the emergence and rapid spread of highly transmissible variants combined with slo...
Article
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Trial results for two COVID-19 vaccines suggest at least 90% efficacy against symptomatic disease (VEDIS). It remains unknown whether this efficacy is mediated by lowering SARS-CoV-2 infection susceptibility (VESUSC) or development of symptoms after infection (VESYMP). We aim to assess and compare the population impact of vaccines with different ef...
Article
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Using a mathematical model, we estimated the potential impact in mortality and total infections of completely lifting community nonpharmaceutical interventions when only a small proportion of the population has been fully vaccinated in two states in the US. Lifting all community nonpharmaceutical interventions immediately is predicted to result in...
Article
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Most COVID-19 vaccines require two doses, however with limited vaccine supply, policymakers are considering single-dose vaccination as an alternative strategy. Using a mathematical model combined with optimization algorithms, we determined optimal allocation strategies with one and two doses of vaccine under various degrees of viral transmission. U...
Article
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Background Cholera is an acute, diarrheal disease caused by Vibrio cholerae O1 or 139 that is associated with a high global burden. Methods We analyzed the estimated duration of immunity following cholera infection from available published studies. We searched PubMed and Web of Science for studies of the long-term immunity following cholera infect...
Preprint
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Most of the COVID-19 vaccines require two doses, at least 3 weeks apart. In the first few months of vaccine deployment, vaccine shortages will be inevitable. Current vaccine prioritization guidelines for COVID-19 vaccines all assume two-dose vaccine deployment. However, vaccinating twice as many people with a single dose of vaccine might be a bette...
Preprint
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Background Several COVID-19 vaccine candidates are in the final stage of testing. Interim trial results for two vaccines suggest at least 90% efficacy against symptomatic disease (VE DIS ). It remains unknown whether this efficacy is mediated predominately by lowering SARS-CoV-2 infection susceptibility ( VE SUSC ) or development of symptoms after...
Preprint
Full-text available
A vaccine, when available, will likely become our best tool to control the current COVID-19 pandemic. Even in the most optimistic scenarios, vaccine shortages will likely occur. Using an age-stratified mathematical model, we determined optimal vaccine allocation for four different metrics (deaths, symptomatic infections, and maximum non-ICU and ICU...
Article
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Background Cholera was introduced into Haiti in 2010. Since then, more than 820 000 cases and nearly 10 000 deaths have been reported. Oral cholera vaccine (OCV) is safe and effective, but has not been seen as a primary tool for cholera elimination due to a limited period of protection and constrained supplies. Regionally, epidemic cholera is conta...
Preprint
Full-text available
Cholera is an acute, diarrheal disease caused by Vibrio cholerae O1 or 139 that is associated with a high global burden. While it is accepted that natural immunity against cholera infection exists, no clear correlate of protection has been identified. In this review, we identify the estimated duration of immunity following cholera infection with an...
Article
By April 2, 2020, >1 million persons worldwide were infected with severe acute respiratory syndrome coronavirus 2. We used a mathematical model to investigate the effectiveness of social distancing interventions in a mid-sized city. Interventions reduced contacts of adults >60 years of age, adults 20–59 years of age, and children <19 years of age f...
Preprint
Full-text available
SARS-CoV-2 has infected over 140,000 people as of March 14, 2020. We use a mathematical model to investigate the effectiveness of social distancing interventions lasting six weeks in a middle-sized city in the US. We explore four social distancing strategies by reducing the contacts of adults over 60 years old, adults over 60 years old and children...
Article
Full-text available
Vaccines, when available, will likely become our best tool to control the COVID-19 pandemic. Even in the most optimistic scenarios, vaccine shortages will likely occur. Using an age-stratified mathematical model paired with optimization algorithms, we determined optimal vaccine allocation for four different metrics (deaths, symptomatic infections,...
Preprint
Full-text available
Background Cholera was introduced into Haiti in 2010. Since, there have been over 820,000 reported cases and nearly 10,000 deaths. The year 2019 has seen the lowest reported number of cases since the epidemic began. Oral cholera vaccine (OCV) is safe and effective, but has generally not been seen as a primary tool for cholera elimination due to a l...
Article
Full-text available
Background: The effectiveness of the live attenuated influenza vaccine (LAIV) can vary widely, ranging from 0 - 50%. The reasons for these discrepancies remain largely unclear. Methods: We use mathematical models to explore how the efficacy of LAIV is affected by the degree of mismatch with the currently circulating influenza strain and interfer...
Preprint
Live-attenuated vaccines are usually highly effective against many acute viral infections. However, the effective- ness of the live attenuated influenza vaccine (LAIV) can vary widely, ranging from 0% effectiveness in some studies done in the United States to 50% in studies done in Europe. The reasons for these discrepancies remain largely unclear....
Article
Full-text available
Human herpesviruses (HHV) establish lifelong latent infection and are transmitted primarily via shedding at mucosal surfaces. Each HHV causes a unique spectrum of disease depending on the infected individual’s age and immunity. We collected weekly oral swabs from young children and mothers in 32 Ugandan households for a median of one year. We chara...
Article
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Cytomegalovirus (CMV) infection occurs frequently in young children, who are then a major source of transmission. Oral CMV shedding by 14 infants with primary infection was comprehensively characterized using quantitative PCR weekly for >9 months. Three phases of oral shedding were identified: expansion, transition, and clearance. Viral expansion o...
Article
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Influenza A virus subtype H5N1 has been a public health concern for almost 20years due to its potential ability to become transmissible among humans. Phase I and II clinical trials have assessed safety, reactogenicity and immunogenicity of inactivated influenza A/H5N1 virus vaccines. A shortage of vaccine is likely to occur during the first months...
Article
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Avian influenza A (H7N9), emerged in China in April 2013, sparking fears of a new, highly pathogenic, influenza pandemic. In addition, avian influenza A (H5N1) continues to circulate and remains a threat. Currently, influenza H7N9 vaccines are being tested to be stockpiled along with H5N1 vaccines. These vaccines require two doses, 21 days apart, f...
Article
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Unlabelled: Untreated human immunodeficiency virus (HIV) infection is characterized by depletion of CD4(+) T cells, ultimately leading to the impairment of host immune defenses and death. HIV-infected CD4(+) T cells die from direct virus-induced apoptosis and CD8 T-cell-mediated elimination, but a broader and more profound depletion occurs in unin...
Data
Epidemic prevention potential (EPP) with 95% bootstrapped CI for five million doses with lower vaccine efficacies. A) One-third of their original values (, and ). B) Two-thirds of their original values (, and ). For each panel, each point in the graph corresponds to the attack rate for a single vaccination day, either on day 5, 10, 15, 30, 60, or 9...
Data
Epidemic prevention potential (EPP) for with 95% bootstrapped CI and the epidemic was seeded in Jakarta. Each panel represents a given number of vaccine doses available to distribute in the network. A) Two million doses. B) Four million doses. C) Five million doses. D) Six million doses. E) Seven million doses. F) Ten million doses. Each point in e...
Data
Epidemic prevention potential (EPP) with 95% bootstrapped CI for five million doses with different travel probabilities. A) An infectious symptomatic individual is 10% less likely to travel than an asymptomatic individual. B) An infectious symptomatic individual is 75% less likely to travel than an asymptomatic individual. For each panel, each poin...
Data
Results for five million doses when children have a 50% reduction in their probability of travel. A) Attack rates with 95% bootstrapped CI. B) EPP with 95% bootstrapped CI. For each panel, each point in the graph corresponds to the attack rate for a single vaccination day, either on day 5, 10, 15, 30, 60, or 90 after the beginning of the epidemic....
Data
Results for five million doses when vaccines are given to children only. A) Attack rates with 95% bootstrapped CI. B) EPP with 95% bootstrapped CI. For each panel, each point in the graph corresponds to the attack rate for a single vaccination day, either on day 5, 10, 15, 30, 60, or 90 after the beginning of the epidemic. (TIF)
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Epidemic curves for the 16 cities considered in the baseline case. The epidemic is started in Jakarta, with 10 infectious individuals. (TIF)
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Epidemic prevention potential (EPP) starting in Taipei with 95% bootstrapped CI. Three different allocations are shown in each panel. Each panel represents a given number of vaccine doses available to distribute in the network. A) Two million doses. B) Four million doses. C) Five million doses. D) Six million doses. E) Seven million doses. F) Ten m...
Data
Attack rate with 95% bootstrapped CI for five million doses with different travel probabilities. A) An infectious symptomatic individual is 10% less likely to travel than an asymptomatic individual. B) An infectious symptomatic individual is 75% less likely to travel than an asymptomatic individual. For each panel, each point in the graph correspon...
Data
Attack rate with 95% bootstrapped CI for five million doses with lower vaccine efficacies. A) One-third of their original values (, and ). B) Two-thirds of their original values (, and ). For each panel, each point in the graph corresponds to the attack rate for a single vaccination day, either on day 5, 10, 15, 30, 60, or 90 after the beginning of...
Data
Results for five million doses when vaccination is completed in 10 days. A) Attack rates with 95% bootstrapped CI. B) EPP with 95% bootstrapped CI. For each panel, each point in the graph corresponds to the attack rate for a single vaccination day, either on day 5, 10, 15, 30, 60, or 90 after the beginning of the epidemic. (TIF)
Article
Full-text available
With new cases of avian influenza H5N1 (H5N1AV) arising frequently, the threat of a new influenza pandemic remains a challenge for public health. Several vaccines have been developed specifically targeting H5N1AV, but their production is limited and only a few million doses are readily available. Because there is an important time lag between the e...
Article
Full-text available
Previous influenza pandemics (1918, 1957, and 1968) have all had multiple waves. The 2009 pandemic influenza A (H1N1) (pandemic H1N1) started in April 2009 and was followed, in the United States (US) and temperate Northern Hemisphere, by a second wave during the fall of 2009. The ratio of susceptible and immune individuals in a population at the en...
Data
Animation of a simulated pandemic H1N1 2009-like pandemic. The simulation was initialized with 1,000 infected individuals in Mexico City on March 29 with . Red dots on the map indicate cities with infected individuals, with the size of the dot proportional to prevalence. Light blue arcs indicate that an infected person travels to a city with no inf...
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Animation of a simulated pandemic beginning in Hong Kong. The simulation was initialized with 1,000 infected individuals in Hong Kong on June 1 with . (MPG)
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Influenza seasons in the model. Each row of symbols represents the seasonality of a single city over the course of a year, with the exception of the first row, which represents all cities north of Lahore, Pakistan. Cities labeled in red are Northern (above Tropic of Cancer), those in green are in the tropics, and those in blue are Southern. Red tri...
Data
Sensitivity of the model results to the symptomatic vs healthy travel ratio. Top panel: The model was run for a pandemic H1N1-like scenario, starting on March 29 with 1,000 individuals infected with a strain with . The symptomatic to healthy travel ratio was varied from 0% to 100%. For each value of this ratio, the simulation was run 10 times, and...
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Sensitivity of the model results to population age structure. Top panel: The model was run for a pandemic H1N1-like scenario, starting on March 29 with 1,000 individuals infected with a strain with . In the default scenario (in black), the fraction of children in the population of each country was based on [16]. In the alternative scenario (in red)...
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Influenza season data from the literature. (PDF)
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Attack rate with 95% bootstrapped CI for a single intervention for six different vaccination days considered and six different vaccination coverages for an epidemic starting in Hong Kong. Each panel represents a given number of vaccine doses available to distribute in the entire network: A) Two million doses. B) Four million doses. C) Five million...
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Model parameters. (PDF)
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Model. (PDF)
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Pandemic simulations. (PDF)
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Diagram of how vaccine roll-out occurs in the model. In the model, we target a set of age cohorts each year for vaccination. The numbers in the diagrams indicate the ages of the population cohorts in years. The numbers in black in each row indicate the cohorts targeted each year, while the numbers in red indicate those already protected by vaccine...
Data
Fitting the model to the 1968–69 Hong Kong pandemic. Top panel: Estimates of R and the pandemic start date. We varied R in increments of 0.05 and the pandemic start date (day on which 1,000 people are infected in Hong Kong) in increments of one week. We ran the simulation twice for each combination of values and chose the results with the smaller e...
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The effect of vaccination on influenza prevalence in the model by hemisphere. Top: For a 1968–1969-like pandemic, we assumed that it began with 1,000 infected individuals in Hong Kong on June 1 with R = 1.4 and vaccination occurred 180 days later in late November. Bottom: For a 2009-like pandemic, we assumed that the pandemic started with 1,000 inf...
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Observed and simulated pandemic H1N1 2009 epidemic peaks. Observed data was from influenza A virology surveillance data from Flunet. (PDF)
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Animation of simulated pandemics beginning in Mexico, with or without vaccination. The simulation was initialized with 1,000 infected individuals in Mexico City on April 1 with . The top panels show a map and the prevalence of infection when there is no vaccine available, while the bottom panels correspond to the simulation in which vaccine was adm...
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Fitting the model to pandemic H1N1 2009. Top panel: Estimates of R and the pandemic start date. We varied R in increments of 0.05 and the pandemic start date (day on which 1,000 people are infected in Mexico City) in increments of one week. We ran the simulation once for each combination of values. The numbers in the plot are the -square values. Do...
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Observed and simulated 1968–1969 pandemic peaks. Observed data is from [3]. (PDF)
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Vaccine availability in different countries in the model. (PDF)
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Cities in the 13 transmission clusters from the global model, in decreasing order of flow. (PDF)
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Mapping global influenza transmission. (PDF)
Article
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New strains of influenza spread around the globe via the movement of infected individuals. The global dynamics of influenza are complicated by different patterns of influenza seasonality in different regions of the world. We have released an open-source stochastic mathematical model of the spread of influenza across 321 major, strategically located...
Article
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Mathematical and computer models can provide guidance to public health officials by projecting the course of an epidemic and evaluating control measures. The authors built upon an existing collaboration between an academic research group and the Los Angeles County, California, Department of Public Health to plan for and respond to the first and sub...
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Vaccine efficacy as a function of time. Plot of the vaccine efficacies modeled as functions of time. Once vaccine is administered, the vaccine efficacies build up in time in an exponentially-like fashion during the first 15 days and remain constant afterward. The exact formula is given in Text S1. (0.02 MB PDF)
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Sensitivity analysis for the basic reproduction number R0 for a developed country. Vaccine distribution by group, for a developed country, with vaccine enough to cover 15% of the population, minimizing deaths for R0 = 1.4, R0 = 1.6 and R0 = 1.8 and set of respective dates considered. As R0 increases, the optimal solution shifts the tiping point whe...
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Sensitivity analysis for adjusting influenza-related mortality and hospitalizations in a LDC setting. Percentage of the total number of doses used in each sub-group in a less developed country when there is enough vaccine to protect 15% of the population and the objective function was set to minimize hospitalizations. The left panel shows the optim...
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Parameter values. (0.06 MB PDF)
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Results for a Developed Country with R0 = 1.8. (0.08 MB PDF)
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Results for a Less Developed Country, influenza-related mortality and hospitalizations adjusted, R0 = 1.4. (0.07 MB PDF)
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Sensitivity analysis for adjusting influenza-related mortality and hospitalizations in a LDC setting. Percentage of the total number of doses used in each sub-group in a less developed country when there is enough vaccine to protect 25% of the population and the objective function was set to minimize mortality. The left panel shows the optimal valu...
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Times considered for starting vaccination for each R0. (0.03 MB PDF)
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Results for a Developed Country with R0 = 1.4. (0.09 MB PDF)
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Results for a Less Developed Country, influenza-related mortality and hospitalizations unadjusted, R0 = 1.8. (0.07 MB PDF)
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Final illness attack rates for the developed country setting for the range of basic reproduction numbers considered. (0.03 MB PDF)
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Results for a Less Developed Country, influenza-related mortality and hospitalizations unadjusted, R0 = 1.4. (0.07 MB PDF)
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Results for a Less Developed Country, influenza-related mortality and hospitalizations adjusted, R0 = 1.8. (0.07 MB PDF)
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Supplemental material for ‘Optimizing vaccine allocation at different points in time during an epidemic’. (0.11 MB PDF)
Article
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Pandemic influenza A(H1N1) 2009 began spreading around the globe in April of 2009 and vaccination started in October of 2009. In most countries, by the time vaccination started, the second wave of pandemic H1N1 2009 was already under way. With limited supplies of vaccine, we are left to question whether it may be a good strategy to vaccinate the hi...