Mathematical modeling of pertussis transmission: evaluating the impact of delayed vaccination in infants

FABRICIUS G; PESCO P; BERGERO P; HOZBOR D

Erice

Conferencia; Mathematical and Computational Epidemiology of Infectious diseases ? the interplay between models and public health policies.; 2015

Mathematical modeling of pertussis transmission: evaluating the impact ofdelayed vaccination in infants.*G.Fabricius*(*), P.Pesco(*), P.Bergero(*) and D. Hozbor(**)(*) Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas,Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CONICET,CC 16, Suc. 4, 1900 La Plata, Argentina.(**) Laboratorio VacSal. Instituto de Biotecnología y Biología Molecular,Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas,Universidad Nacional de La Plata y CCT-La Plata, CONICET. Calles 47 y 115(1900) La Plata, Argentina.The incidence of the highly contagious respiratory disease named pertussisor whooping cough has been increasing for the past two decades in severalcountries despite the highly extended vaccination. The reasons for thisresurgence are a matter of discussion and, while trying to understand thiscomplex problem, new strategies that include more boosters for adolescentsand adults have been adopted in many countries in an attempt to improve thecontrol of the disease. However, the impact of these measures on infants(the risk age group) is not clear. In this context mathematical models arebeing increasingly used to study the disease transmission and to estimatethe impact of different control strategies. In previous work, we developedan age structured deterministic mathematical model with 9 epidemiologicalclasses to evaluate the effect of an adolescent booster on pertussis infantincidence [1]. We have also applied the model to explore different possiblecauses for pertussis resurgence that are compatible with observedepidemiological data [2].  In this contribution, recent improvementsintroduced into the model to evaluate the effect of delays in theadministration of the first three vaccination doses are described. Themethodology involves the consideration of additional epidemiologicalclasses to keep track of the number of doses administered to the populationindependently of their immune status [3]. Using data gathered fromvaccination centers in urban and suburban areas in an Argentine city, weevaluated the impact on infant incidence of reducing the observed delays invaccine administration. We conclude that reducing delays in vaccination orimproving the coverage of the first doses are measures with a highpotential impact on the risk age group, clearly higher than the inclusionof an adolescent or adult booster at a given age. Robustness of the resultswas checked for different sets of parameters representing differentpossible epidemiological scenarios.[1] "Modeling pertussis transmission to evaluate the effectiveness of anadolescent booster in  Argentina".       G.Fabricius, P.Bergero,  M.Ormazabal, A.Maltz and D. Hozbor.       Epidemiology and Infection 141, 718-734 (2013).[2] "Modelling the effect of changes in vaccine effectiveness andtransmission contact rates on pertussis epidemiology".       P. Pesco, P.Bergero, G. Fabricius and D. Hozbor.       Epidemics 7, 13-21 (2014).[3] "Mathematical modeling of delayed pertussis vaccination in infants".       P. Pesco, P.Bergero, G. Fabricius and D. Hozbor.       Accepted for publication in Vaccine on 1st July 2015