Epidemiological and Clinical data of Bordetella pertussis Infection among Children Younger than One-year-old Treated in a University Hospital in Northern Mexico

Background: Despite being one of the most vaccine preventable diseases that affect children and adults, Pertussis incidence has had a gradual increase in the past several years. Vaccination strategies have been implemented across different age groups and patient populations, specifically to include pregnant women. Nonetheless, vaccine coverage remains low. We sought to analyze the epidemiological and clinical data of Bordetella pertussis infection among children less than one year-old in a university hospital in Mexico.

 

Methods: Retrospective analysis of all patients younger than one year of age diagnosed with B. pertussis infection by RT-PCR and/or culture. Epidemiological and clinical data were collected.

 

Results: During the study period, 33 patients were diagnosed with whooping cough by positive PCR. Patients mean age was 1.6 months (± 1.06). The infection was most frequent in May, June, and September. Hospital stay was 7.0 ± 4.85 days and mean duration of symptoms was of 8.60 ± 6.66 days. A paroxysmal cough was observed in 93.1%, cyanosis 82.8% and 51.7% presented productive cough. Complications developed in 30.8% and mortality occurred 6.3%. The mothers’ mean age was 23.61 ± 6.33 years and only 12.5% were vaccinated during pregnancy; 56% had only middle school education. Mothers had an average number of 6.83 ±3.89 prenatal consults during the pregnancy. This cohort of mothers of infected children was relatively young, only a third were married, and 80% had a low level of education; factors that surely play a key role in non-compliance with vaccination. 

We hypothesize that if half of our cohort had been vaccinated during pregnancy, the absolute risk reduction would be 0.22 (95% CI 329.2-746.4) with a number needed to treat (NNT) of 457. This means that one in every 457 patients will benefit from the treatment.

Conclusion: Pertussis was a frequent infection; with higher frequency in May, June, and September and showing a trending increase through the years. There is a great need to optimize immunization strategies, both actively, in the child, and passively through the mother, and continue strict epidemiological surveillance.  

 

Figure 1. Number of cases per month. Mean number of cases per month was 2.66 (horizontal line).