Disclaimer: Early release articles are not considered as final versions. Any changes will be reflected in the online version in the month the article is officially released.
Volume 32, Number 10—October 2026
Research Letter
Age Differences in Pertussis Epidemics, New South Wales, Australia, 2015 and 2024
Ella F. Madden
, Sally L. Ellis, Andrea Parisi, Christine E. Selvey, and Janaki Amin
, Sally L. Ellis, Andrea Parisi, Christine E. Selvey, and Janaki Amin
Table
Demographic characteristics of pertussis cases notified in New South Wales, Australia, 2015 and 2024*
| Characteristic | Notifications |
Rate, cases/100,000 population† |
IRR, 2024 vs. 2015 (95% CI) | |||
|---|---|---|---|---|---|---|
| 2015 | 2024 | 2015 | 2024 | |||
| Age group | ||||||
| <1 y | 336 (2.80) | 503 (1.96) | 342.47 | 505.03 | 1.47 (1.28–1.69) | |
| 0–5 mo | 171 (1.42) | 232 (0.90) | 348.58 | 516.33 | 1.48 (1.22–1.8) | |
| 6–11 mo | 165 (1.37) | 271 (1.05) | 336.35 | 603.13 | 1.79 (1.48–2.18) | |
| 1–4 y | 1,477 (12.30) | 1,641 (6.39) | 372.04 | 431.54 | 1.16 (1.08–1.24) | |
| 5–9 y | 3,020 (25.15) | 5,964 (23.21) | 617.39 | 1,187.25 | 1.92 (1.84–2.01) | |
| 10–14 y | 2,666 (22.20) | 9,762 (37.99) | 594.18 | 1,904.40 | 3.21 (3.07–3.35) | |
| 15–24 y | 981 (8.17) | 2,738 (10.66) | 99.50 | 275.72 | 2.77 (2.58–2.98) | |
| 25–34 y | 645 (5.37) | 859 (3.34) | 57.77 | 73.85 | 1.28 (1.15–1.42) | |
| 35–44 y | 905 (7.54) | 1,185 (4.61) | 87.96 | 105.64 | 1.2 (1.1–1.31) | |
| 45–54 y | 853 (7.10) | 1,332 (5.18) | 86.51 | 131.25 | 1.52 (1.39–1.65) | |
| >55 |
1,124 (9.36) |
1,711 (6.66) |
54.41 |
71.95 |
1.32 (1.23–1.43) |
|
| Sex | ||||||
| M | 5,607 (46.70) | 12,883 (50.14) | 148.47 | 317.32 | 2.14 (2.07–2.21) | |
| F | 6,386 (53.19) | 12,801 (49.82) | 166.32 | 311.78 | 1.87 (1.82–1.93) | |
| Unknown/other |
13 (0.11) |
10 (0.04) |
NA |
NA |
NA |
|
| Median age, y (IQR) |
11 (7–33) |
11 (9–17) |
NA |
NA |
NA |
|
| Total cases | 12,007 (100.0) | 25,695 (100.0) | 157.65 | 314.68 | 2 (1.95–2.04) | |
*Values are no. (%) cases except as indicated. IRR, incidence rate ratio. NA, not applicable. †As no population was available for the groups 0–5 mo and 6–11 mo, the total population estimates for people <1 years of age in 2015 and 2024 respectively was halved. Those populations were then used for rate calculations.
Page created: August 07, 2026
Page updated: September 22, 2026
Page reviewed: September 22, 2026
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.