[A matched case-control study on the effectiveness of acellular pertussis-containing vaccine among children aged 4...

Objective: To evaluate the vaccine effectiveness (VE) of acellular pertussis vaccine (aPV) in children aged 4 months to 6 years. Methods: Children aged 4 months to 6 years presenting with cough at sentinel surveillance hospitals in Jiangsu Province in 2024 and undergoing pertussis laboratory testing were enrolled. A case-control study design was employed, with pertussis nucleic acid test-positive cases selected in the case group. A 1∶1 individual matching method was used to select the control group, with matching factors including identical or adjacent residential subdistrict/township, same gender, birth date within ±1 month, and no history of pertussis in the control group. A total of 893 cases and 893 controls were included in the study. Demographic data and immunisation information were collected from the sentinel hospital information management system and the Jiangsu Province Childhood Immunisation Information System. Conditional logistic regression models were used to analyse the VE of aPV, calculated as VE=(1-OR)×100%. Results: Males accounted for 58.12% (519 cases) in both the case group and the control group. There was no statistically significant difference in age distribution between the two groups (P=0.380). The overall VE of aPV against pertussis was 74.87% (95%CI: 60.46%-84.64%). The VE for doses 1, 2, 3, and 4 of aPV was 45.88% (95%CI:-3.72%-72.00%), 73.81% (95%CI: 48.64%-86.91%), 78.62% (95%CI: 65.52%-87.20%), and 74.42% (95%CI: 59.49%-84.45%), respectively. The VE after completing 4 doses of vaccination with time intervals of 1-11, 12-23, 24-35, and 36-54 months was 79.89% (95%CI: 65.94%-88.48%), 78.39% (95%CI: 64.03%-87.43%), 76.23% (95%CI: 60.56%-86.13%), and 70.61%(95%CI:51.50%-82.75%), respectively. Conclusion: aPV has a good overall VE in preventing pertussis in children. After the final dose of vaccination, VE shows a decreasing trend over time.