Pertussis-related infant mortality was associated with leukocytosis and pulmonary hypertension, according to findings from a case-control study published in BMC Infectious Diseases.

Investigators analyzed medical records from infants (N=59) aged 4 months or younger who were admitted for severe pertussis. Of these, 54.2% were boys and 3.3% of infants had been vaccinated.

The infants presented with cough and cyanosis (n=57), atrial septal defect (n=18), pulmonary hypertension (n=11), and patent ductus arteriosus (n=2). The majority of patients had coinfections (86%) including respiratory syncytial virus (n=13), Haemophilus influenzae (n=13), Klebsiella pneumoniae (n=13), influenza B (n=3), and adenovirus (n=3). Nearly all patients (90%) required respiratory support.


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Among the severe cases, 15 (29.4%) resulted in infant death. Infant death was significantly associated with symptoms of apnea (80.00% vs 31.80%; P =.001), leukocytosis (≥30×109/L; 93.33% vs 43.18%; P =.001), and pulmonary hypertension (57.14% vs 8.33%; P =.001). Analyses found that these factors were also independently associated with infant mortality apnea (P =.004; P =.005; P =.017, respectively).

The infants who died had significantly greater peak white blood cell count (77.33±28.56 vs 30.52±16.46; P =.00) and lymphocyte count (29.59±13.59 vs 16.19±9.20; P =.00) compared to infants who survived.

This study was limited by its low sample size and its retrospective design.

The study authors concluded there was a high mortality rate from severe pertussis among unvaccinated infants. Infants who presented with leukocytosis, pulmonary hypertension, and apnea were at higher risk for death. These data may indicate that vaccination guidelines among infants need to be reevaluated such that infants may be protected at a younger age.

Reference

Liu C, Yang L, Cheng Y, Xu H, Xu F. Risk factors associated with death in infants <120 days old with severe pertussis: a case-control study. BMC Infect Dis. 2020;20(1):852. doi:10.1186/s12879-020-05535-0