"Let’s have a yarn about the whooping cough vaccine", will bring together expectant First Nations women, who live in the Southern NSW Local Health District (SNSWLDH) to ‘yarn’ about the pertussis vaccine. Yarning will be facilitated by First Nations peoples. At least five yarning circles will be organised, hosted in Goulburn, Queanbeyan, Moruya, Bega, and Cooma.
Additional yarning circles will be flexible, ensuring inclusivity and accommodating the needs of the community. This initiative’s overarching goal is to foster shared decision-making, enhance pertussis vaccine uptake, and mitigate vaccine hesitancy within this demographic. A secondary outcome will be the development of an acceptable culturally appropriate vaccines information leaflet (s), co-developed with First Nations Women who live in the area to meet their information needs
– “women’s business”.

Introduction
Pertussis notification rates were at an all-time low during the COVID-19 pandemic. There was a resurgence of cases in Australia in 2024, with NSW recording the most cases since it became notifiable in 1991. We compared the characteristics of the epidemic of 2024 to the previous NSW epidemic in 2015.
Methods
A retrospective observational analysis was conducted using data from the NSW notifiable conditions database (NCIMS). Notification rates in 2015 and 2024 were compared by age group, sex, and remoteness as defined by the accessibility/Remoteness Index of Australia Plus (ARIA+) and incidence rate ratios (IRR) were calculated.
Results
In 2024, there were 25,694 pertussis notifications, more than double the 12,007 in 2015. The annual rate per 100,000 population doubled from 158 in 2015 to 315 in 2024 (IRR: 2.00, 95% Confidence Interval (CI): 1.95 - 2.04).
In 2015, the highest rates were in the 5-9 and 10-14-year age groups (617 and 594 per 100,000 population, respectively). In 2024, rates increased across all age groups, with the highest rates observed in the 10-14 age group (1,904 per 100,000), followed by the 5-9 age group (1,187 per 100,000). The largest increase was in the 10-14-year age group (IRR: 3.21, 95% CI: 3.07 - 3.35).
In 2015, rates were higher for females than males (166 vs. 149 per 100,000). In 2024, rates increased for both groups, with a more pronounced increase in males (317 vs. 312 per 100,000 population; IRR: 2.14 vs. 1.87).
Conclusion
We quantified a shift in pertussis notifications to older children between the epidemics of 2015 and 2024. Reduced pertussis circulation during the COVID-19 pandemic extended the duration between cyclical epidemics that naturally occur due to waning immunity. This disruption in exposure timing likely contributed to older children having lower-than-expected immunity and consequently higher rates of disease.

Background: For pertussis, public health follow-up of children <10 years of age is standard practice in Victoria. In response to epidemic levels of pertussis in 2024, the Ovens Murray Public Health Unit (OMPHU) expanded follow-up to include a convenient sample of cases aged ≥10. We assessed the implications of this expanded follow-up on identifying high-risk contacts and outbreaks

Methods: All OMPHU-catchment pertussis cases and outbreaks reported between 1 January 2024 and 24 January 2025 to Victoria’s notifiable diseases database were extracted. The presence of a risk factor (defined as either having a high-risk contact or attending a high-risk setting while infectious) was compared by age group (<10 or ≥10). High-risk contacts were defined as children <6 months or pregnant women, and high-risk settings were defined as maternity or neonatal units.

Results: 272 cases were followed up by OMPHU. Of these, 121 (44.5%) were followed up according to protocol (i.e., <10 years of age), while 151 (55.5%) were part of the expanded follow-up response. Among cases <10 years, 36.4% (n=44) had an identified risk factor, while 26.5% (n=40) of cases ≥10 years had an identified risk factor (Chi² test: p=0.080). Nine school outbreaks were detected during the follow-up of cases aged ≥10, with the first cases in each outbreak being ≥10, in addition to seven outbreaks identified through routine follow-up. Region-specific issues, including limited testing capacity and treatment shortages, were identified and addressed.

Conclusion: Expanding pertussis case follow-up to cases aged ≥10 years was effective for identifying high-risk contacts and additional outbreaks, particularly outbreaks in school settings. No significant difference in the identification of risk factors between age groups was found, meaning that older cases were just as likely to have a high-risk contact or have attended a high-risk setting while infectious. Although resource-intensive, expanded follow-up could be considered during epidemics.

Background

From early 2024 Tasmania experienced an increase in Bordetella pertussis notifications, consistent with national trends and previous epidemics. We analysed notifications from January 2024 to February 2025 to explore if school holidays were associated with reduced transmission.

Methods

We compared the average number of weekly notifications in school-aged children (5-17 years) and all ages in term and holiday periods (29 vs 18 weeks respectively) using an independent T-test.
Additionally, we compared notifications in school-aged children in the 3 weeks before and 3 weeks after commencement of school holidays for the holiday periods within the established epidemic.
Holiday and term periods were defined using public school dates, adjusted by 7 days to account for the pertussis incubation.

Results

In total there were 1055 cases, with 623 (59%) aged 5-17 years. The average weekly number of cases in holiday periods compared with term periods was 43% lower in children 5-17 years (7.2 vs 12.7, p<0.05), and 58% lower among children 12-17 years (2.2 vs 5.3, p<0.01). For cases 18 years and over, differences were negligible (6.2 vs 6.1, p=0.9).
Among children 5-17 years, the period following commencement of school holidays was associated with fewer cases than the preceding school term period with a reduction in total cases from 28 to 13 (54%), 93 to 73 (22%) and 78 to 36 (54%) across the 3 holiday periods respectively.

Discussion and conclusion

School holidays were associated with reduced pertussis notifications in school-aged children, with fewer weekly average notifications in holidays and a reduction immediately following commencement of holidays. This may be due to school holidays acting as a ‘circuit breaker’, with reduced mixing of these age groups leading to decreased transmission. These finding prompt consideration of the specific settings that contribute most to pertussis transmission, and interventions that may reduce this risk.

Background
Combination vaccines incorporating antigens that protect against multiple diseases reduce the number of injections infants need to receive and have been shown to be safe and highly effective. To efficiently protect infants over a short time frame, Australia’s immunisation schedule involves co-administration of a variety of combination vaccines over the first months of life.

There are two main types of combination vaccines that protect against pertussis - whole-cell (wP) which contains inactivated pertussis bacteria and acellular pertussis (aP), which is a subunit vaccine. wP is more reactogenic but more protective against pertussis infection than aP. The two vaccine types also induce different immune profiles.

Stage 1 of OPTIMUM, a blinded, adaptive, randomised, controlled trial (ACTRN12617000065392), randomised Australian infants in a 1:1 ratio to receive either wP- or aP-containing vaccines as their first pertussis dose, co-administered with other scheduled vaccines.

This study investigated the immune impact of wP and aP as a first pertussis dose on the response to co-administered antigens of pneumococcal (13vPCV), Haemophilus influenzae type b (Hib-PRP) and hepatitis B (HBsAg).

Results and Outcomes
Between March 2018 and January 2020, 150 infants were randomised (75 per study arm). In infants receiving wP, antibody responses (IgG GMR) to all 13vPCV serotypes and Hib-PRP at 6, 7, 18, and 19 months old, as well as to HBsAg at 6 and 7 months old were non-inferior (>90% probability) to those in aP-receiving infants. In many instances, responses were superior in the wP-primed group for 13vPCV serotypes, Hib-PRP, and HBsAg compared to the aP-primed group.

Conclusion
This study provides evidence of the differing immunomodulatory effect of a wP primed schedule on co-administered vaccine responses compared to the standard schedule. While the impact of these effects remains uncertain, they highlight the possibility of harnessing co-administration of vaccines for the augmentation of vaccine immunity.

Background: Pertussis is a highly contagious, endemic respiratory disease in Australia, with cyclical increases every two to five years despite high levels of vaccination coverage. Low pertussis activity was reported from 2020-2023. From March 2024, there was a pertussis epidemic in Australia with the highest number of cases reported to National Notifiable Diseases Surveillance System (NNDSS) in a single year.
Methods: We analysed pertussis cases reported to the NNDSS between 1 January 1995 and 31 December 2024 by age groups and single year of age.
Results: Of 57,134 pertussis notifications in 2024, rates were highest in adolescents aged 10-14 years and children aged 5-9 years, with the highest notification rate by single year of age being in children aged 11 years (1,890.7 notifications per 100,000 population). The proportion of pertussis cases in adolescents aged 10-12 years was substantially higher in 2024 (29.4%) compared with recent epidemic peaks 2009-2011 (9.2%) and 2015-2016 (14.9%). Infants less than 6 months accounted for a lower proportion of cases (0.9%) than in previous epidemic years from 1995 (range 1.4%-4.3%), representing shifting trends where the highest rates were observed in this age group prior to 2014.
Conclusion: The record number of pertussis notifications in 2024 may be partly due to reduced pertussis activity during 2020-2023 resulting in a higher proportion of susceptible individuals in the population. This coupled with waning immunity in adolescents aged 10-14 years who were last eligible for a funded booster at 4 years may have driven the highest rates reported in this age group. Other factors include decreasing vaccination coverage post-COVID-19 and changing testing practices. Australia boasts relatively high vaccination coverage in pregnant people with a funded vaccine available since 2015 in all states and territories. The lower proportion of pertussis in infants in 2024 compared with previous periods likely indicates the success of this strategy in protecting this vulnerable age group.

Objective: The study aimed to evaluate maternal vaccine coverage and determinants of uptake among pregnant women in South Australia.
Methods: This retrospective cohort study included 19,098 pregnant women who delivered at the Women’s and Children’s Hospital in South Australia between January 2020 and December 2023. Poisson regression models were used to estimate adjusted prevalence ratios (aPRs) to identify factors influencing vaccine uptake. Results: Overall, 64.1% received the influenza vaccine, 74.1% pertussis, 59.7% both, and 24.8% ≥1 COVID-19 dose during pregnancy. Late initiation of antenatal care and multiparity were both associated with lower uptake of all three maternal vaccines. Women with a history of pregnancy loss had lower influenza uptake (aPR 0.97, 95% CI: 0.94–0.99) but higher pertussis uptake (aPR 1.02, 95% CI: 1.00–1.05). Maternal smoking was associated with lower uptake of the influenza vaccine (aPR 0.92, 95% CI: 0.87–0.97). First Nations women had lower pertussis uptake (aPR 0.86, 95% CI: 0.82–0.91), while culturally and linguistically diverse (CALD) women had higher uptake of influenza (aPR 1.05, 95% CI: 1.03–1.07) and pertussis vaccines (aPR 1.02, 95% CI: 1.00–1.04). Women whose infants were discharged to alternative care, such as adoption, had lower pertussis uptake (aPR 0.91, 95% CI: 0.84–0.98). Lower vaccine uptake was observed among women attending midwifery-led care (influenza: aPR 0.95, 95% CI: 0.92–0.98; pertussis: aPR 0.91, 95% CI: 0.89–0.94; COVID-19: aPR 0.82, 95% CI: 0.75–0.90). In contrast, attending private maternity care (aPR 1.24, 95% CI: 1.13–1.35) and receiving shared antenatal care (aPR 1.17, 95% CI: 1.10–1.24) were associated with higher COVID-19 vaccine uptake. Influenza and pertussis uptake declined from 2021–2023 compared to 2020, while COVID-19 uptake increased tenfold in 2022 and fivefold in 2023 compared to 2021.
Conclusion: Maternal vaccine uptake varies by maternity care model, patient-provider interactions, and sociodemographic factors.