Epidemiological characteristics and vaccination history analysis of pertussis in Quzhou from 2005 to 2024.

BACKGROUND

Despite high vaccination coverage, pertussis is reemerging in China and increasingly affecting older children. This shift challenges current immunization strategies. To inform better prevention, we aimed to investigate pertussis epidemiology in Quzhou, with a focus on analyzing factors linked to the time between vaccination and illness onset among diagnosed cases.

METHODS

We analyzed pertussis cases from the China Information System for Disease Control and Prevention (CISDCP) in Quzhou City (2005-2024) and linked them to vaccination records from the Zhejiang Immunization Program Smart Service Information System. The outcome variable was the time from the last vaccine dose to pertussis diagnosis.

RESULTS

During 2005-2024, Quzhou reported 2,045 pertussis cases, with 93.25% concentrated in 2024. Case distribution shifted from 0 to 4 to ≥ 5 years (P < 0.001). Age‑specific incidence rose markedly in all groups in 2024 (all P < 0.001), with the highest rate observed among 5-9‑year‑olds (878.99/100,000). Among cases with known vaccination history, 83.86% had received at least one dose. Multivariable Cox regression showed that vaccination status and vaccine type were significantly associated with pertussis risk. Pertussis risk was 45% lower after the fourth dose than before it (P = 0.017). For vaccine type comparisons versus DTaP, the hazard ratio for pertussis was 0.11 for DTwP, 2.09 for DTaP-Hib, and 3.28 for DTaP-IPV/Hib (all P < 0.001).

CONCLUSIONS

The 2024 pertussis outbreak in Quzhou showed a marked age shift toward school-aged children, with the highest incidence in 5-9-year-olds. Our findings support adding a booster dose at 6 years of age and reconsidering multivalent DTaP-containing vaccines.