David N Fisman

University of Toronto, Toronto, Ontario, Canada

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Publications (169)908.77 Total impact

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    ABSTRACT: Highly transmissible genes encoding resistance to carbapenems have demonstrated global spread. The New Delhi Metallo-beta-lactamase 1 gene is hypothesized to have originated in India, with subsequent dissemination by colonized or infected travelers. We conducted an ecological study evaluating the association between the cumulative air traffic departing India between 2007 and 2012 and published cases of NDM-1. Receiver operator characteristic curves were generated as well as multivariate logistic regression models. 193 countries with complete flight and World Bank data were included in the analysis. Receiver operator characteristic curves (ROC) of the dichotomous outcome of a published case of NDM-1 were generated, yielding an unadjusted area under the curve (AUC) of 0.88 and adjusted AUC of 0.85. The unadjusted odds ratio of having a reported case of NDM-1, for every percentage increase in cumulative air traffic departing India, was 2.3 (95% CI 1.4 to 3.7) and adjusted was 2.0 (95% CI 1.2 to 3.4). We demonstrate that flows of international travelers departing India by air is associated with published NDM-1 cases, globally. Countries with high passenger flight traffic from India with no reported cases of NDM-1 may be at increased risk of having unreported transmission of NDM-1. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Travel Medicine and Infectious Disease 06/2015; DOI:10.1016/j.tmaid.2015.06.003 · 1.54 Impact Factor
  • Ashleigh Tuite, David Fisman
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    ABSTRACT: Syphilis outbreaks in urban men who have sex with men (MSM) are an ongoing public health challenge in many high-income countries, despite intensification of efforts to screen and treat at-risk individuals. We sought to understand how population-level coverage of asymptomatic screening impacts the ability to control syphilis transmission. We developed a risk-structured deterministic compartmental mathematical model of syphilis transmission in a population of sexually active MSM. We assumed a baseline level of treatment of syphilis cases due to seeking medical care in all scenarios. We evaluated the impact of sustained annual population-wide screening coverage ranging from 0% to 90% on syphilis incidence over the short term (20 years) and at endemic equilibrium. The relationship between screening coverage and equilibrium syphilis incidence displayed an inverted U-shape relationship, with peak equilibrium incidence occurring with 20-30% annual screening coverage. Annual screening of 62% of the population was required for local elimination (incidence <1 case per 100 000 population). Results were qualitatively similar in the face of differing programmatic, behavioural and natural history assumptions, although the screening thresholds for local elimination differed. With 6-monthly or 3-monthly screening, the population coverage required to achieve local elimination was reduced to 39% or 23%, respectively. Although screening has the potential to control syphilis outbreaks, suboptimal coverage may paradoxically lead to a higher equilibrium infection incidence than that observed in the absence of intervention. Suboptimal screening programme design should be considered as a possible contributor to unsuccessful syphilis control programmes in the context of the current epidemic. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
    Sexually transmitted infections 05/2015; DOI:10.1136/sextrans-2014-052001 · 3.08 Impact Factor
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    ABSTRACT: Only a portion of hospital-acquired Clostridium difficile infections can be traced back to source patients identified as having symptomatic disease. Antibiotic exposure is the main risk factor for C difficile infection for individual patients and is also associated with increased asymptomatic shedding. Contact with patients taking antibiotics within the same hospital ward may be a transmission risk factor for C difficile infection, but this hypothesis has never been tested. To obtain a complete portrait of inpatient risk that incorporates innate patient risk factors and transmission risk factors measured at the hospital ward level and to investigate ward-level rates of antibiotic use and C difficile infection risk. A 46-month (June 1, 2010, through March 31, 2014) retrospective cohort study of inpatients 18 years or older in a large, acute care teaching hospital composed of 16 wards, including 5 intensive care units and 11 non-intensive care unit wards. Patient-level risk factors (eg, age, comorbidities, hospitalization history, antibiotic exposure) and ward-level risk factors (eg, antibiotic therapy per 100 patient-days, hand hygiene adherence, mean patient age) were identified from hospital databases. Incidence of hospital-acquired C difficile infection as identified prospectively by hospital infection prevention and control staff. A total of 255 of 34 298 patients developed C difficile (incidence rate, 5.95 per 10 000 patient-days; 95% CI, 5.26-6.73). Ward-level antibiotic exposure varied from 21.7 to 56.4 days of therapy per 100 patient-days. Each 10% increase in ward-level antibiotic exposure was associated with a 2.1 per 10 000 (P < .001) increase in C difficile incidence. The association between C difficile incidence and ward antibiotic exposure was the same among patients with and without recent antibiotic exposure, and C difficile risk persisted after multilevel, multivariate adjustment for differences in patient-risk factors among wards (relative risk, 1.34 per 10% increase in days of therapy; 95% CI, 1.16-1.57). Among hospital inpatients, ward-level antibiotic prescribing is associated with a statistically significant and clinically relevant increase in C difficile risk that persists after adjustment for differences in patient-level antibiotic use and other patient- and ward-level risk factors. These data strongly support the use of antibiotic stewardship as a means of preventing C difficile infection.
    JAMA Internal Medicine 02/2015; 175(4). DOI:10.1001/jamainternmed.2014.8273 · 13.25 Impact Factor
  • Ashleigh McGirr, David N Fisman
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    ABSTRACT: Pertussis incidence is increasing, possibly due to the introduction of acellular vaccines, which may have decreased the durability of immune response. We sought to evaluate and compare the duration of protective immunity conferred by a childhood immunization series with 3 or 5 doses of diphtheria-tetanus-acellular pertussis (DTaP). We searched Medline and Embase for articles published before October 10, 2013. Included studies contained a measure of long-term immunity to pertussis after 3 or 5 doses of DTaP. Twelve articles were eligible for inclusion; 11 of these were included in the meta-analysis. We assessed study quality and used meta-regression models to evaluate the relationship between the odds of pertussis and time since last dose of DTaP and to estimate the probability of vaccine failure through time. We found no significant difference between the annual odds of pertussis for the 3- versus 5-dose DTaP regimens. For every additional year after the last dose of DTaP, the odds of pertussis increased by 1.33 times (95% confidence interval: 1.23-1.43). Assuming 85% vaccine efficacy, we estimated that 10% of children vaccinated with DTaP would be immune to pertussis 8.5 years after the last dose. Limitations included the statistical model extrapolated from data and the different study designs included, most of which were observational study designs. Although acellular pertussis vaccines are considered safer, the adoption of these vaccines may necessitate earlier booster vaccination and repeated boosting strategies to achieve necessary "herd effects" to control the spread of pertussis. Copyright © 2015 by the American Academy of Pediatrics.
    Pediatrics 01/2015; 135(2). DOI:10.1542/peds.2014-1729 · 5.30 Impact Factor
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    ABSTRACT: Evaluate safety and efficacy of Incobotulinumtoxin A in elderly patients with dementia and paratonia. University-affiliated hospital, spasticity management Clinic. Ten subjects were enrolled. 1) severe cognitive impairment 2) diagnosis of Alzheimer's disease, vascular dementia, or frontotemporal dementia, and 3) score >3 on the paratonic assessment instrument, with posture in an arm(s) interfering with provision of care. 1) alternate etiologies for increased tone and 2) injection with botulinum toxin within the 6 months preceding the study. Single center, randomized, double blind, placebo-controlled, crossover trial with two treatment cycles of 16 weeks. Assessments occurred at 2, 6, 12 and16 weeks following injections. Subjects received up to 300 U of Incobotulinumtoxin A in arm(s). Primary outcome measure was the modified caregiver burden scale (mCBS); exploratory secondary outcome measures were also performed. Analysis of variance and mixed modeling techniques were used to evaluate treatment effects. Incobotulinumtoxin A treatment produced significant improvement in mCBS total score -1.11 (-2.04 to -0.18) (Treatment effect and 95% CI), dressing sub-score -0.36 (-0.59 to 0.12), and cleaning under the left and right armpits sub-score -0.5 (-0.96 to -0.04), -0.41 (-0.79 to -0.04) respectively. PROM in the left and right elbow increased by 27.67 degrees (13.32-42.02) and 22.07 degrees (9.76-34.39) respectively. PROM in the left and right shoulder increased by 11.92 degrees (5.46-18.38) and 8.58 degrees (3.73-13.43) respectively. No significant treatment effect was found for GAS, VAS and PAINAD scales or change in time to perform care. No adverse drug reactions occurred. Administration of Incobotulinumtoxin A in elderly people with advanced dementia and paratonia may be an efficacious and safe treatment to increase range of motion and reduce functional burden. Further studies are needed to confirm results. ClinicalTrials.Gov NCT02212119.
    PLoS ONE 12/2014; 9(12):e114733. DOI:10.1371/journal.pone.0114733 · 3.53 Impact Factor
  • PLoS ONE 12/2014; · 3.53 Impact Factor
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    ABSTRACT: Infections due to Gram-negative bacteria exhibit seasonal trends, with peak infection rates during warmer months. We hypothesized that the likelihood of a bloodstream infection due to Gram-negative bacteria increases with proximity to the equator. We tested this hypothesis and identified geographical, climatic and social factors associated with this variability. We established a network of 23 international centers in 22 cities. Setting: De-identified results of positive blood cultures from 2007-2011 and data sources for geographic, climatic and socioeconomic factors were assembled for each center. Patients at the 23 centers with positive blood cultures. Due to variability in the availability of total culture volumes across sites, our primary outcome measure was the fraction of positive blood cultures that yielded Gram-negative bacteria; sources of variability in this outcome measure were explored using meta-regression techniques. The mean fraction of bacteremia associated with Gram-negative bacteria was 48.4% (range 26.4% to 61.8%). Although not all sites displayed significant seasonality, the overall P-value for seasonal oscillation was significant (P<0.001). In univariate meta-regression models, temperature, latitude, latitude squared, longitude, per capita gross domestic product and percent of gross domestic product spent on healthcare were all associated with the fraction of bacteremia due to Gram-negative bacteria. In multivariable models, only percent of gross domestic product spent on healthcare and distance from the equator (ie. latitude squared) were significantly associated with the fraction of bacteremia due to Gram-negative bacteria. The likelihood of bacteremia due to Gram-negative bacteria varies markedly between cities, in a manner that appears to have both geographic (latitude) and socioeconomic (proportion gross domestic product devoted to health spending) determinants. Thus, the optimal approach to initial management of suspected bacteremia may be geographically specific. The rapid emergence of highly antibiotic-resistant Gram-negative pathogens may have geographically specific impacts.
    PLoS ONE 12/2014; 9(12):e114548. DOI:10.1371/journal.pone.0114548 · 3.53 Impact Factor
  • David Fisman, Ashleigh R Tuite
    The Lancet Infectious Diseases 12/2014; 14(12):1164-5. DOI:10.1016/S1473-3099(14)70851-5 · 19.45 Impact Factor
  • David Fisman, Edwin Khoo, Ashleigh Tuite
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    ABSTRACT: The 2014 West African Ebola virus outbreak, now more correctly referred to as an epidemic, is the largest ever to occur. As of August 28, 2014, concerns have been raised that control efforts, particularly in Liberia, have been ineffective, as reported case counts continue to increase. Limited data are available on the epidemiology of the outbreak. However, reported cumulative incidence data as well as death counts are available for Guinea, Sierra Leone, Liberia and Nigeria. We utilized a simple, two parameter mathematical model of epidemic growth and control, to characterize epidemic growth patterns in West Africa, to evaluate the degree to which the epidemic is being controlled, and to assess the potential implications of growth patterns for epidemic size. Models demonstrated good fits to data. Overall basic reproductive number (R0) for the epidemic was estimated to be between 1.6 and 2.0, consistent with prior outbreaks. However, we identified only weak evidence for the occurrence of epidemic control in West Africa as a whole, and essentially no evidence for control in Liberia (though slowing of growth was seen in Guinea and Sierra Leone). It is projected that small reductions in transmission would prevent tens of thousands of future infections. These findings suggest that there is an extraordinary need for improved control measures for the 2014 Ebola epidemic, especially in Liberia, if catastrophe is to be averted.
    09/2014; 6. DOI:10.1371/currents.outbreaks.89c0d3783f36958d96ebbae97348d571
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    ABSTRACT: Antibiotic therapy is the principal risk factor for Clostridium difficile infection (CDI), but little is known about how risks cumulate over the course of therapy and abate after cessation. We prospectively identified CDI cases among adults hospitalized at a tertiary hospital between June 2010 and May 2012. Poisson regression models included covariates for time since admission, age, hospitalization history, disease pressure, and intensive care unit stay. Impacts of antibiotic use through time were modeled using 4 measures: current antibiotic receipt, time since most recent receipt, time since first receipt during a hospitalization, and duration of receipt. Over the 24-month study period, we identified 127 patients with new onset nosocomial CDI (incidence rate per 10,000 patient days [IR] = 5.86). Of the 4 measures, time since most recent receipt was the strongest independent predictor of CDI incidence. Relative to patients with no prior receipt of antibiotics in the last 30 days (IR = 2.95), the incidence rate of CDI was 2.41 times higher (95% confidence interval [CI] 1.41, 4.13) during antibiotic receipt and 2.16 times higher when patients had receipt in the prior 1-5 days (CI 1.17, 4.00). The incidence rates of CDI following 1-3, 4-6 and 7-11 days of antibiotic exposure were 1.60 (CI 0.85, 3.03), 2.27 (CI 1.24, 4.16) and 2.10 (CI 1.12, 3.94) times higher compared to no prior receipt. These findings are consistent with studies showing higher risk associated with longer antibiotic use in hospitalized patients, but suggest that the duration of increased risk is shorter than previously thought.
    PLoS ONE 08/2014; 9(8):e105454. DOI:10.1371/journal.pone.0105454 · 3.53 Impact Factor
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    ABSTRACT: To discuss the potential for systematically incorporating economic evaluation into immunization decision-making in Canada, the Vaccine Industry Committee of BIOTECanada, together with the Public Health Agency of Canada, academic vaccine researchers, economists, and modelers, held a workshop titled 'Economic Evaluation in Immunization Decision Making'. The workshop brought together multiple interested parties to discuss opportunities and challenges in the Canadian system, learn about proposed best practices in this field, and consult about the optimal use of economic analysis in an overall coherent vaccine decision-making framework. Participants were asked to reflect on how economic evaluation can best fit in Canada, whether current standards for economic evaluation are sufficient, and how and by whom these evaluations should be conducted. In this paper, we summarize the workshop presentations and consultations as well as insights about what approaches may be needed and feasible in Canada.
    Expert Review of Vaccines 07/2014; 13(11):1-6. DOI:10.1586/14760584.2014.939637 · 4.22 Impact Factor
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    Ashleigh R Tuite, Ann N Burchell, David N Fisman
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    ABSTRACT: Syphilis co-infection risk has increased substantially among HIV-infected men who have sex with men (MSM). Frequent screening for syphilis and treatment of men who test positive might be a practical means of controlling the risk of infection and disease sequelae in this population.
    PLoS ONE 07/2014; 9(7):e101240. DOI:10.1371/journal.pone.0101240 · 3.53 Impact Factor
  • Kevin A Brown, David N Fisman, Nick Daneman
    Infection Control and Hospital Epidemiology 07/2014; 35(7):911-912. DOI:10.1086/676881 · 3.94 Impact Factor
  • Marija Vasilevska, Jennifer Ku, David N Fisman
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    ABSTRACT: Background and objective. Healthcare workers experience occupational risk of infection and may transmit infections to patients. Vaccination provides an efficient means of protecting workers and patients, but uptake may be low. We sought to identify factors influencing vaccine acceptance by healthcare workers in order to obtain insights leading to more effective vaccination programs in this population. Design. Systematic review and meta-analysis. Methods. We searched Medline, Embase, and CINAHL databases to identify studies published up to May 2012. Factors influencing vaccination acceptance were devised a priori. Random-effects meta-analysis was performed to generate summary estimates of effect. Heterogeneity and publication bias were explored using statistical tools. Results. Thirty-seven studies evaluating a variety of vaccines (against influenza, pertussis, smallpox, anthrax, and hepatitis B) were included. Homogeneous effects on vaccine acceptance were identified with desire for self-protection (odds ratio [OR], 3.42 [95% confidence interval (CI), 2.42-4.82]) and desire to protect family and friends (OR, 3.28 [95% CI, 1.10-9.75]). Concern that vaccine transmits the illness it was meant to prevent decreased acceptance (OR, 0.42 [95% CI, 0.30-0.58]). Differences in physician and nurse acceptance of immunization were seen between Asian and non-Asian studies. Conclusions. Consideration of self-protection (rather than absolute disease risk or protection of patients) appears the strongest and most consistent driver of healthcare workers' decisions to accept vaccination, though other factors may also be impactful, and reasons for between-study divergence in effects is an important area for future research. This finding has important implications for the design of programs to enhance healthcare worker vaccine uptake.
    Infection Control and Hospital Epidemiology 06/2014; 35(6):699-708. DOI:10.1086/676427 · 3.94 Impact Factor
  • David N Fisman, Gabriel M Leung, Marc Lipsitch
    The Lancet 01/2014; 383(9913):189-90. DOI:10.1016/S0140-6736(13)62123-6 · 45.22 Impact Factor
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    ABSTRACT: In the 19th century, there were several major cholera pandemics in the Indian subcontinent, Europe, and North America. The causes of these outbreaks and the genomic strain identities remain a mystery. We used targeted high-throughput sequencing to reconstruct the Vibrio cholerae genome from the preserved intestine of a victim of the 1849 cholera outbreak in Philadelphia, part of the second cholera pandemic. This O1 biotype strain has 95 to 97% similarity with the classical O395 genome, differing by 203 single-nucleotide polymorphisms (SNPs), lacking three genomic islands, and probably having one or more tandem cholera toxin prophage (CTX) arrays, which potentially affected its virulence. This result highlights archived medical remains as a potential resource for investigations into the genomic origins of past pandemics.
    New England Journal of Medicine 01/2014; 370:334-340. DOI:10.1056/NEJMoa1308663 · 54.42 Impact Factor
  • David Fisman, Ashleigh Tuite
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    ABSTRACT: The 2014 West African Ebola outbreak has evolved into an epidemic of historical proportions and catastrophic scope. Prior outbreaks have been contained through the use of personal protective equipment, but such an approach has not been rapidly effective in the current epidemic. Several candidate vaccines have been developed against the Ebola virus, and are undergoing initial clinical trials. As removal of population-level susceptibility through vaccination could be a highly impactful control measure for this epidemic, we sought to estimate the number of vaccine doses and timing of vaccine administration required to reduce the epidemic size. Our base model was fit using the IDEA approach, a single equation model that has been successful to date in describing Ebola growth. We projected the future course of the Ebola epidemic using this model. Vaccination was assumed to reduce the effective reproductive number. We evaluated the potential impact of vaccination on epidemic trajectory under different assumptions around timing of vaccine availability. Using effective reproductive (Re) number estimates derived from this model, we estimate that 3-4 million doses of vaccine, if available and administered, could reduce Re to 0.9 in the interval from January-March 2015. Later vaccination would be associated with a progressively diminishing impact on final epidemic size; in particular, vaccination to the same Re at or after the epidemic is projected to peak (April-May 2015) would have little impact on final epidemic size, though more intensive campaigns (e.g., Re reduced to 0.5) could still be effective if initiated by summer 2015. In summary, there is a closing window of opportunity for the use of vaccine as a tool for Ebola epidemic control. Effective vaccination, used before the epidemic peaks, would be projected to prevent tens of thousands of deaths; this does not minimize the ethical challenges that would be associated with wide-scale application of vaccines that have undergone only limited evaluation for safety and efficacy.
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    ABSTRACT: The Middle East Respiratory Syndrome Coronavirus (MERS-CoV) was initially recognized as a source of severe respiratory illness and renal failure in 2012. Prior to 2014, MERS-CoV was mostly associated with sporadic cases of human illness, of presumed zoonotic origin, though chains of person-to-person transmission in the healthcare setting were reported. In spring 2014, large healthcare-associated outbreaks of MERS-CoV infection occurred in Jeddah and Riyadh, Kingdom of Saudi Arabia. To date the epidemiological information published by public health investigators in affected jurisdictions has been relatively limited. However, it is important that the global public health community have access to information on the basic epidemiological features of the outbreak to date, including the basic reproduction number (R0) and best estimates of case-fatality rates (CFR). We sought to address these gaps using a publicly available line listing of MERS-CoV cases. R0 was estimated using the incidence decay with exponential adjustment ("IDEA") method, while period-specific case fatality rates that incorporated non-attributed death data were estimated using Monte Carlo simulation. 707 cases were available for evaluation. 52% of cases were identified as primary, with the rest being secondary. IDEA model fits suggested a higher R0 in Jeddah (3.5-6.7) than in Riyadh (2.0-2.8); control parameters suggested more rapid reduction in transmission in the former city than the latter. The model accurately projected final size and end date of the Riyadh outbreak based on information available prior to the outbreak peak; for Jeddah, these projections were possible once the outbreak peaked. Overall case-fatality was 40%; depending on the timing of 171 deaths unlinked to case data, outbreak CFR could be higher, lower, or equivalent to pre-outbreak CFR. Notwithstanding imperfect data, inferences about MERS-CoV epidemiology important for public health preparedness are possible using publicly available data sources. The R0 estimated in Riyadh appears similar to that seen for SARS-CoV, but CFR appears higher, and indirect evidence suggests control activities ended these outbreaks. These data suggest this disease should be regarded with equal or greater concern than the related SARS-CoV.
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    ABSTRACT: Communicable disease outbreaks of novel or existing pathogens threaten human health around the globe. It would be desirable to rapidly characterize such outbreaks and develop accurate projections of their duration and cumulative size even when limited preliminary data are available. Here we develop a mathematical model to aid public health authorities in tracking the expansion and contraction of outbreaks with explicit representation of factors (other than population immunity) that may slow epidemic growth. The Incidence Decay and Exponential Adjustment (IDEA) model is a parsimonious function that uses the basic reproduction number R0, along with a discounting factor to project the growth of outbreaks using only basic epidemiological information (e.g., daily incidence counts). Compared to simulated data, IDEA provides highly accurate estimates of total size and duration for a given outbreak when R0 is low or moderate, and also identifies turning points or new waves. When tested with an outbreak of pandemic influenza A (H1N1), the model generates estimated incidence at the i+1(th) serial interval using data from the i(th) serial interval within an average of 20% of actual incidence. This model for communicable disease outbreaks provides rapid assessments of outbreak growth and public health interventions. Further evaluation in the context of real-world outbreaks will establish the utility of IDEA as a tool for front-line epidemiologists.
    PLoS ONE 12/2013; 8(12):e83622. DOI:10.1371/journal.pone.0083622 · 3.53 Impact Factor
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    ABSTRACT: Despite highly successful vaccination programs and high vaccine uptake, both endemic pertussis and periodic pertussis outbreaks continue to occur. The under-recognized role of adolescents and adults in disease transmission, due to waning immunity following natural infection and vaccination, and reduced likelihood of correct diagnosis, may contribute to pertussis persistence. We constructed a mathematical model to describe the transmission of pertussis in Southern Ontario in both pre-vaccine and vaccine eras, to estimate the underlying burden of pertussis in the population. The model was well calibrated using the best available data on pertussis in the pre-vaccination (1880-1929) and vaccination (1993-2004) eras in Ontario. Pertussis under-reporting by age group was estimated by comparing model-projected incidence to reported laboratory-confirmed cases for Greater Toronto. Best-fit model estimates gave a basic reproductive number of approximately 10.6, (seasonal range 9.9 to 11.5). Under-reporting increased with age, and approximately >95% of infections in children were caused by infections in persons with waning immunity to pertussis following prior infection or vaccination. A well-calibrated model suggests that under-recognized cases of pertussis in older individuals are likely to be an important driver of ongoing pertussis outbreaks in children. Model projections strongly support enhancement of booster vaccination efforts in adults.
    PLoS ONE 12/2013; 8(12):e83850. DOI:10.1371/journal.pone.0083850 · 3.53 Impact Factor

Publication Stats

4k Citations
908.77 Total Impact Points


  • 2007–2015
    • University of Toronto
      • • Dalla Lana School of Public Health
      • • Institute of Health Policy, Management and Evaluation
      Toronto, Ontario, Canada
  • 2008–2013
    • SickKids
      Toronto, Ontario, Canada
    • Ontario Ministry Of Health And Long-Term Care
      Toronto, Ontario, Canada
  • 2011
    • Mount Sinai Hospital, Toronto
      • Department of Microbiology
      Toronto, Ontario, Canada
  • 2009–2011
    • Public Health Ontario
      Toronto, Ontario, Canada
    • The University of Calgary
      • Department of Pathology and Laboratory Medicine
      Calgary, Alberta, Canada
  • 2002–2008
    • McMaster University
      • Department of Clinical Epidemiology and Biostatistics
      Hamilton, Ontario, Canada
  • 2004–2007
    • Drexel University
      • • School of Public Health
      • • Department of Epidemiology and Biostatistics
      Filadelfia, Pennsylvania, United States
  • 2006
    • Princeton University
      • Center for Health and Wellbeing
      Princeton, NJ, United States
  • 2005
    • Drexel University College of Medicine
      Philadelphia, Pennsylvania, United States
  • 2001
    • Harvard Medical School
      Boston, Massachusetts, United States
    • Beth Israel Deaconess Medical Center
      • Division of Infectious Diseases
      Boston, MA, United States