Estimating the excess burden of pertussis disease in Australia within the first year of life, that might have been prevented through timely vaccination. (13th September 2022)

• Record Type: Journal Article
• Authors: Jayasundara, Duleepa; Randall, Deborah; Sheridan, Sarah; Sheppeard, Vicky; Liu, Bette; Richmond, Peter C; Blyth, Christopher C; Wood, James G; Moore, Hannah C; McIntyre, Peter B; Gidding, Heather F
• Is Part Of: International journal of epidemiology. Volume 52:Number 1(2023)
• Page Start: 250
• Page End: 259
• Publication Date: 2022-09-13
• Subjects: Pertussis -- propensity score weighting -- vaccination timeliness; Epidemiology -- Periodicals; 614.4
• DOI: 10.1093/ije/dyac175
• Languages: English
• ISSNs: 0300-5771

Abstract

Abstract: Background: Previous Australian studies have shown that delayed vaccination with each of the three primary doses of diphtheria-tetanus-pertussis-containing vaccines (DTP) is up to 50 % in certain subpopulations. We estimated the excess burden of pertussis that might have been prevented if (i) all primary doses and (ii) each dose was given on time. Methods: Perinatal, immunization, pertussis notification and death data were probabilistically linked for 1 412 984 infants born in two Australian states in 2000–12. A DTP dose administered >15 days after the recommended age was considered delayed. We used Poisson regression models to compare pertussis notification rates to 1-year of age in infants with ≥1 dose delayed (Aim 1) or any individual dose delayed (Aim 2) versus a propensity weighted counterfactual on-time cohort. Results: Of all infants, 42% had ≥1 delayed DTP dose. We estimated that between 39 to 365 days of age, 85 (95% CI: 61–109) cases per 100 000 infants, could have been prevented if all infants with ≥1 delayed dose had received their three doses within the on-time window. Risk of pertussis was higher in the delayed versus the on-time cohort, so crude rates overestimated the excess burden (110 cases per 100 000 infants (95% CI: 95–125)). The estimated dose-specific excess burden per 100 000 infants was 132 for DTP1, 50 for DTP2 and 19 for DTP3. Conclusions: We provide robust evidence that improved DTP vaccine timeliness, especially for the first dose, substantially reduces the burden of infant pertussis. Our methodology, using a potential outcomes framework, is applicable to other settings.