Real-World Effectiveness of 3 Types of Acellular Pertussis Vaccines Among Children Aged 3 Months-16 Years in Lu'an, China: A Matched Case-Control Study

Background The real-world vaccine effectiveness (VE) of the diphtheria, tetanus, and acellular pertussis (DTaP), DTaP-Haemophilus influenzae type b (Hib), and DTaP-inactivated polio (IPV)/Hib vaccines has not been thoroughly evaluated in China. Additionally, there are limited data on the VE of acellular pertussis-containing vaccines (aPVs) when used interchangeably.Methods We conducted a matched case-control study to estimate the VE of aPVs against polymerase chain reaction-confirmed pertussis infection in Lu'an in 2024. A conditional logistic regression model was used to compare the odds ratios (ORs) of vaccination between cases and controls. VE was calculated as [(1 - adjusted OR) x 100%], and 95% confidence intervals (CIs) were computed around the estimates.Results A total of 1936 children aged 3 months to 16 years were included in the study. The overall VE was 77.3% (95% CI, 35.2%-92.1%). The VE for fully vaccinated children was 88.4% (95% CI, 57.3%-96.8%), while the VE for partially vaccinated children was 77.4% (95% CI, 35.5%-92.1%). The VE of DTaP, DTaP-Hib, and DTaP-IPV/Hib was 75.8% (95% CI, 29.7%-91.7%), 83.2% (95% CI, 47.8%-94.6%), and 79.8% (95% CI, 36.5%-93.6%), respectively. Compared with mixed vaccination (65.3%.), the incremental VE of DTaP, DTaP-Hib, and DTaP-IPV/Hib was 31.0% (95% CI, 1.0%-51.9%), 52.9% (95% CI, 19.1%-72.6%), and 41.1% (95% CI, -18.7% to 71.8%), respectively. We observed a decline in VE over time, decreasing from 76.5% (95% CI, 33.0%-91.7%) within the first 2 years to -5.5% (95% CI, -495.2% to 81.3%) after 6 years or more.Conclusions All aPVs provide significant protection against pertussis infection, although this protection wanes over time. The VE appears to decrease materially if these vaccines are administered alternately in an individual's routine immunization schedule.