Abstract
BackgroundPertussis remain a global health concern, especially in infants too young to initiate their vaccination. Effective vaccination and high coverage limit the circulation of the pathogen, yet duration of protection is limited and boosters are recommended during a lifetime. In Iran, boosters are given at 18 months and 6 years old using whole pertussis vaccines for which efficacy is not known, and pertussis surveillance is scant with only sporadic biological diagnosis. Burden of pertussis is not well understood and local data are needed.MethodsHospital-based prospective study implementing molecular laboratory testing in infants aged ≤6 months and presenting ≥5 days of cough associated to one pertussis-like symptom in Tehran. Household and non-household contact cases of positive infants were evaluated by comprehensive pertussis diagnosis (molecular testing and serology) regardless of clinical signs. Clinical evaluation and source of infection were described.ResultsA total of 247 infants and 130 contact cases were enrolled. Pertussis diagnosis result was obtained for 199 infants and 104 contact cases. Infant population was mostly < 3 months old (79.9%; 157/199) and unvaccinated (62.3%; 124/199), 20.1% (40/199) of them were confirmed having B. pertussis infection. Greater cough duration and lymphocyte counts were the only symptoms associated to positivity. Half of the contact cases (51.0%; 53/104) had a B. pertussis infection, median age was 31 years old. A proportion of 28.3% (15/53) positive contacts did not report any symptom. However, 67.9% (36/53) and 3.8% (2/53) of them reported cough at inclusion or during the study, including 20.8% (11/53) who started coughing ≥7 days before infant cough onset. Overall, only five samples were successfully cultured.ConclusionThese data evidenced the significant prevalence of pertussis infection among paucy or poorly symptomatic contacts of infants with pertussis infection. Widespread usage of molecular testing should be implemented to identify B. pertussis infections.
Highlights
Pertussis is a highly contagious respiratory disease caused by Bordetella pertussis or, in a lower extent, Bordetella parapertussis, typically transmitted through airborne droplets
It remains an important cause of morbidity and mortality among infants too young to have initiated their primary vaccine series, who account for the majority of pertussis related complications, hospitalizations and deaths
This study aimed at improving our knowledge of pertussis in infants with whooping cough syndrome in Tehran, Iran, and at better understanding the source of infection by analyzing the close contacts of infected infants
Summary
Pertussis (whooping cough) is a highly contagious respiratory disease caused by Bordetella pertussis or, in a lower extent, Bordetella parapertussis, typically transmitted through airborne droplets. Mass vaccination led to an important decrease in pertussis incidence, the pathogen still circulates worldwide even in countries where vaccine coverage is high in infants and young children. It remains an important cause of morbidity and mortality among infants too young to have initiated their primary vaccine series, who account for the majority of pertussis related complications, hospitalizations and deaths. To limit the period of vulnerability for infants, the World Health Organization (WHO) recommends to initiate the pertussis vaccination at 6 weeks of age and no later than 8 weeks, and maintain high coverage (≥90%) with at least three doses of quality assured pertussis vaccine [2, 3]. Burden of pertussis is not well understood and local data are needed
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