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Hospital-based prospective study of pertussis in infants and close contacts in Tehran, Iran
Gaelle Noel1, Masoumeh Nakhost Lotfi2, Sajedeh Mirshahvalad2
1Center for Translational Science, Institut Pasteur, Paris, France. gaelle.noel@pasteur.fr.
Insights
Pertussis remains a global concern, particularly for unvaccinated infants. Molecular testing is crucial for identifying Bordetella pertussis infections in infants and their contacts, including asymptomatic individuals.
Area of Science:
- Infectious Diseases
- Microbiology
- Public Health
Background:
- Pertussis (whooping cough) poses a significant global health risk, especially to infants too young for vaccination.
- Limited vaccine-induced immunity necessitates booster doses throughout life.
- Iran's pertussis surveillance is limited, with unknown vaccine efficacy and a need for local data.
Purpose of the Study:
- To investigate the prevalence of Bordetella pertussis infection in infants and their contacts in Tehran.
- To evaluate the utility of molecular testing for pertussis diagnosis in a hospital-based setting.
- To understand the clinical presentation and transmission patterns of pertussis.
Main Methods:
- A prospective, hospital-based study involving infants under six months with pertussis-like symptoms.
- Molecular testing (PCR) and serology were used for diagnosing pertussis in infants and their household/non-household contacts.
- Clinical data and infection sources were systematically collected and analyzed.
Main Results:
- 20.1% of infants under six months tested positive for B. pertussis, with most being unvaccinated.
- 51% of evaluated contacts of infected infants were also positive for B. pertussis.
- A significant proportion of infected contacts were asymptomatic or mildly symptomatic, highlighting potential for silent transmission.
Conclusions:
- Pertussis is prevalent among contacts of infected infants, including those with mild or no symptoms.
- Widespread implementation of molecular testing is recommended for accurate B. pertussis identification.
- This study underscores the need for enhanced pertussis surveillance and diagnostic capabilities.
Background:
Pertussis 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.
Methods:
Hospital-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.
Results:
A 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.
Conclusion:
These 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.
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