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Published on: May 19, 2020
Risk Factors Associated With Bordetella pertussis Among Infants ≤4 Months of Age in the Pre-Tdap Era: United States,
Christine Robinette Curtis1, Andrew L Baughman, Chas DeBolt
1From the *Immunization Services Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; †Preventive Medicine Residency, Population Health Workforce Branch, Division of Scientific Education and Professional Development, Center for Surveillance, Epidemiology, and Laboratory Services, Centers for Disease Control and Prevention, Atlanta, Georgia; ‡Epidemic Intelligence Service Program, Epidemiology Workforce Branch, Division of Scientific Education and Professional Development, Center for Surveillance, Epidemiology, and Laboratory Services, Centers for Disease Control and Prevention, Atlanta, Georgia; §Division of Global HIV & TB, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia; ¶Washington State Department of Health, Shoreline, Washington; ‖Public Health-Seattle & King County, Seattle, Washington; **Arizona Department of Health Services, Phoenix, Arizona; ††Infectious Disease Epidemiology, Prevention, and Control Division, Minnesota Department of Health, St. Paul, Minnesota; ‡‡City of Philadelphia Department of Public Health, Philadelphia, Pennsylvania; §§Meningitis and Vaccine Preventable Diseases Branch, Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; and ¶¶ Epidemiology and Surveillance Division, National Immunization Program, Centers for Disease Control and Prevention, Atlanta, Georgia.
Insights
Infants with household contacts experiencing prolonged cough are at higher risk for pertussis. Breastfeeding appears to offer protection against pertussis in infants.
Area of Science:
- Pediatric Infectious Diseases
- Epidemiology
- Immunology
Background:
- Infants in the United States face the highest rates of pertussis incidence and mortality.
- Understanding infant risk factors for pertussis is crucial for enhancing prevention strategies.
Purpose of the Study:
- To identify risk factors for pertussis in infants.
- To evaluate the protective effect of breastfeeding against pertussis.
Main Methods:
- Prospective enrollment of infants under 4 months with confirmed pertussis and matched controls across four sites (2002-2005).
- Structured interviews with caregivers and serologic testing for IgG antibodies against pertussis toxin in infants and contacts.
- Matched case-control study design with multivariable analysis to assess risk factors.
Main Results:
- Infants with household contacts (mother or other) experiencing prolonged new cough (≥5 days) had significantly higher odds of pertussis.
- Breastfeeding, particularly with limited formula supplementation (0-1 feeding/day), was associated with decreased odds of pertussis.
- High seropositivity rates (90%) were observed among tested infant case-patients.
Conclusions:
- Prolonged new cough in household contacts is a significant risk factor for infant pertussis.
- Breastfeeding demonstrates a protective effect against pertussis and should be recommended alongside vaccination strategies.
- Findings support current pertussis prevention measures including maternal and close-contact vaccination.
Background:
In the United States, infants have the highest reported pertussis incidence and death rates. Improved understanding of infant risk factors is needed to optimize prevention strategies.
Methods:
We prospectively enrolled infants ≤4 months of age with incident-confirmed pertussis from 4 sites during 2002-2005 (preceding pertussis antigen-containing vaccination recommendations for adolescents/adults); each case-patient was age and site matched with 2 control subjects. Caregivers completed structured interviews. Infants and their contacts ≥11 years of age were offered serologic testing for IgG; being seropositive was defined as ≥94 antipertussis toxin IgG enzyme-linked immunosorbent assay units per milliliter.
Results:
Enrolled subjects (115 case-patients; 230 control subjects) had 4396 contacts during incubation periods; 83 (72%) case-patients had ≥1 contact with prolonged (≥5 days) new cough in primary or secondary households. In multivariable analysis, the odds for pertussis were higher for infants with primary/secondary household contacts who had a prolonged new cough, compared with infants who did not. These contacts included mother [adjusted matched odds ratio (aMOR), 43.8; 95% confidence interval (CI), 6.45-298.0] and ≥1 nonmother contact (aMOR, 20.1; 95% CI, 6.48-62.7). Infants receiving breast milk with 0-1 formula feedings daily had decreased pertussis odds (aMOR, 0.27; 95% CI, 0.08-0.89), compared with those receiving more formula. Of 41 tested case-patients, 37 (90%) were seropositive.
Conclusions:
Pertussis in infants was associated with prolonged new cough (≥5 days) in infants' household contacts. Findings suggest that breastfeeding protects against pertussis and warrants recommendation with pertussis prevention strategies, which currently include pertussis vaccination of pregnant mothers and infants' close contacts.
