Pertussis-Associated Pneumonia in Infants and Children From Low- and Middle-Income Countries Participating in the PERCH Study

Abstract

Background: Few data exist describing pertussis epidemiology among infants and children in low- and middle-income countries to guide preventive strategies.

Methods: Children 1-59 months of age hospitalized with World Health Organization-defined severe or very severe pneumonia in 7 African and Asian countries and similarly aged community controls were enrolled in the Pneumonia Etiology Research for Child Health study. They underwent a standardized clinical evaluation and provided nasopharyngeal and oropharyngeal swabs and induced sputum (cases only) for Bordetella pertussis polymerase chain reaction. Risk factors and pertussis-associated clinical findings were identified.

Results: Bordetella pertussis was detected in 53 of 4200 (1.3%) cases and 11 of 5196 (0.2%) controls. In the age stratum 1-5 months, 40 (2.3% of 1721) cases were positive, all from African sites, as were 8 (0.5% of 1617) controls. Pertussis-positive African cases 1-5 months old, compared to controls, were more often human immunodeficiency virus (HIV) uninfected-exposed (adjusted odds ratio [aOR], 2.2), unvaccinated (aOR, 3.7), underweight (aOR, 6.3), and too young to be immunized (aOR, 16.1) (all P ≤ .05). Compared with pertussis-negative African cases in this age group, pertussis-positive cases were younger, more likely to vomit (aOR, 2.6), to cough ≥14 days (aOR, 6.3), to have leukocyte counts >20 000 cells/µL (aOR, 4.6), and to have lymphocyte counts >10 000 cells/µL (aOR, 7.2) (all P ≤ .05). The case fatality ratio of pertussis-infected pneumonia cases 1-5 months of age was 12.5% (95% confidence interval, 4.2%-26.8%; 5/40); pertussis was identified in 3.7% of 137 in-hospital deaths among African cases in this age group.

Conclusions: In the postneonatal period, pertussis causes a small fraction of hospitalized pneumonia cases and deaths; however, case fatality is substantial. The propensity to infect unvaccinated infants and those at risk for insufficient immunity (too young to be vaccinated, premature, HIV-infected/exposed) suggests that the role for maternal vaccination should be considered along with efforts to reduce exposure to risk factors and to optimize childhood pertussis vaccination coverage.

Keywords: infant; pertussis; pneumonia; vaccination; whooping cough.

© The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America.

Figures

Figure 1.

Cumulative age distribution of children with severe or very severe pneumonia by pertussis infection status as determined by polymerase chain reaction (PCR) results. A, Children with a positive PCR result for pertussis (n = 53). B, Children whose PCR results were negative (n = 4120). Pertussis-positive children were significantly younger than pertussis-negative children (median, 2 vs 7 months; P = .01, logistic regression adjusted for site, restricted to sites in Africa and Bangladesh where positive cases were found).