title: A change in vaccine efficacy and duration of protection explains recent rises in pertussis incidence in the United States.
abstract: Over the past ten years the incidence of pertussis in the United States (U.S.) has risen steadily, with 2012 seeing the highest case number since 1955. There has also been a shift over the same time period in the age group reporting the largest number of cases (aside from infants), from adolescents to 7-11 year olds. We use epidemiological modelling and a large case incidence dataset to explain the upsurge. We investigate several hypotheses for the upsurge in pertussis cases by fitting a suite of dynamic epidemiological models to incidence data from the National Notifiable Disease Surveillance System (NNDSS) between 1990-2009, as well as incidence data from a variety of sources from 1950-1989. We find that: the best-fitting model is one in which vaccine efficacy and duration of protection of the acellular pertussis (aP) vaccine is lower than that of the whole-cell (wP) vaccine, (efficacy of the first three doses 80% [95% CI: 78%, 82%] versus 90% [95% CI: 87%, 94%]), increasing the rate at which disease is reported to NNDSS is not sufficient to explain the upsurge and 3) 2010-2012 disease incidence is predicted well. In this study, we use all available U.S. surveillance data to: 1) fit a set of mathematical models and determine which best explains these data and 2) determine the epidemiological and vaccine-related parameter values of this model. We find evidence of a difference in efficacy and duration of protection between the two vaccine types, wP and aP (aP efficacy and duration lower than wP). Future refinement of the model presented here will allow for an exploration of alternative vaccination strategies such as different age-spacings, further booster doses, and cocooning.
authors.affiliation: Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia; Modeling Unit, National Center for Immunization and Respiratory Diseases (NCIRD), Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, United States of America; IHRC, Inc., Atlanta, Georgia, United States of America.
authors.forename: Manoj
authors.initials: M
authors.lastname: Gambhir
authors.affiliation: Meningitis and Vaccine Preventable Diseases Branch, Division of Bacterial Diseases, NCIRD, CDC, Atlanta, Georgia, United States of America.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Clark
authors.affiliation: Medical Research Council Centre for Outbreak Analysis and Modelling, Imperial College London, London, United Kingdom; Mathematical Modelling of Infectious Diseases Unit, Institut Pasteur, Paris, France.
authors.forename: Simon
authors.initials: S
authors.lastname: Cauchemez
authors.affiliation: Kaiser Permanente Southern California, Kaiser Permanente Research, Department of Research & Evaluation, Pasadena, California, United States of America.
authors.forename: Sara Y
authors.initials: SY
authors.lastname: Tartof
authors.affiliation: Modeling Unit, National Center for Immunization and Respiratory Diseases (NCIRD), Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, United States of America; Office of Science and Integrative Programs, NCIRD, CDC, Atlanta, Georgia, United States of America.
authors.forename: David L
authors.initials: DL
authors.lastname: Swerdlow
authors.affiliation: Medical Research Council Centre for Outbreak Analysis and Modelling, Imperial College London, London, United Kingdom.
authors.forename: Neil M
authors.initials: NM
authors.lastname: Ferguson
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D003198:Computer Simulation; D015721:Diphtheria-Tetanus-Pertussis Vaccine / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007115:Immunization Schedule; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D015233:Models, Statistical; D011159:Population Surveillance; D018570:Risk Assessment / Q000379:methods; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology; D014611:Vaccination / Q000706:statistics & numerical data*; D064166:Vaccine Potency; D014917:Whooping Cough / Q000453:epidemiology* / Q000517:prevention & control*; D055815:Young Adult
chemical_list: D015721:Diphtheria-Tetanus-Pertussis Vaccine