Epidemiological characteristics of pertussis from 2014 to 2023 and pertussis antibody level in children aged 1−<5 years in Shapingba district of Chongqing

Objective To describe the epidemiological characteristics of pertussis and understand the antibody level in 1−<5 years old population in Shapingba district of Chongqing from 2014 to 2023.

Methods A descriptive epidemiological analysis was conducted on the incidence data of pertussis in Shapingba from 2014 to 2023, which were collected from China Disease Control and Prevention Information System. Blood samples collected from healthy children aged 1−<5 years in Shapingba from September to November, 2022 were used for pertussis antibody level detection with enzyme-linked immunosorbent assay.

Results From 2014 to 2023, a total of 559 cases of pertussis were reported in Shapingba, with an average annual incidence rate of 4.48/100 000. The pertussis cases were distributed in different age groups, i.e. 326 cases in age group ＜1 year (427.06/100 000), 113 cases in age group 1− years (31.49/100 000), 107 cases in age group 5− years ( 17.55/100 000), and 13 cases in age group ≥10 years ( 0.10/100 000). The study found that 64 cases (13.82%) received no dose of diphtheria, tetanus and pertussis (DTP) vaccine at age ≥3 months, 88 cases (20.85%) received less than two doses of DTP vaccine at age ≥4 months, 76 cases (20.77%) received less than three doses of DTP vaccine at age ≥5 months, and 3 cases (1.78%) received less than four doses of DTP vaccine at age ≥18 months. The positive rate of pertussis IgG was 45.83% in age group 1 year, 37.78% in age group 2 years, 13.64% in age group 3 years, and 7.55% in age group 4 years (χ²=27.798, P＜0.01), with corresponding geometric mean concentrations of 71.80, 42.09, 32.71, and 19.23 IU/mL, respectively (F=5.530, P=0.001).

Conclusion Over the past decade, the relatively high and increased incidence of pertussis was observed in Shapingba. The high incidence of pertussis was observed in infants, especially in those receiving no DTP vaccine or receiving less than 3 doses. In children aged 1−<5 years, the level of pertussis antibody significantly decreased with age. It is necessary to strengthen the timely and full-series pertussis vaccination for age-eligible children and improve the childhood pertussis immunization strategy.