Estimating the excess burden of pertussis disease in Australia within the first year of life, that might have been prevented through timely vaccination.

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.

• Authors: Duleepa Jayasundara, Deborah Randall, Sarah Sheridan, Vicky Sheppeard, Bette Liu, Peter C Richmond, Christopher C Blyth, James G Wood, Hannah C Moore, Peter B McIntyre, Heather F Gidding
• Journal: International journal of epidemiology (Int J Epidemiol) Vol. 52 Issue 1 Pg. 250-259 (02 08 2023) ISSN: 1464-3685 [Electronic] England
• PMID: 36099159 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © The Author(s) 2022. Published by Oxford University Press on behalf of the International Epidemiological Association.

Chemical References

• Diphtheria-Tetanus-Pertussis Vaccine
• Haemophilus Vaccines

Topics

• Infant
• Female
• Pregnancy
• Humans
• Aged, 80 and over
• Whooping Cough (epidemiology, prevention & control)
• Australia (epidemiology)
• Diphtheria-Tetanus-Pertussis Vaccine
• Vaccination
• Haemophilus Vaccines