Respiratory Syncytial Virus (RSV) is a leading cause of severe respiratory infections in infants, resulting in significant paediatric hospitalisations and placing a substantial healthcare burden in Australia. In Queensland, despite the availability of effective prevention strategies, including infant immunisation and antenatal maternal vaccination, uptake remains suboptimal. Understanding parental attitudes and barriers to acceptance is critical for enhancing immunisation coverage.

In 2024, Queensland, Australia, experienced approximately a 40% increase in RSV cases compared to the previous year, with confirmed diagnoses rising by over 11,000 to exceed 40,000 cases.1,2 Among these, more than 10,600 children under the age of 2 were diagnosed with RSV, accounting for about a quarter of all infections.2 Additionally, 2,000 children under 2 years old with RSV infection required hospitalisation, highlighting the substantial burden on healthcare services and the potential severity of disease.2

This study aims to explore the demographic, socio-economic, and informational factors influencing parental acceptance of RSV immunisation (Nirsevimab) for infants and antenatal RSV vaccination (Abrysvo) in Wide Bay, Queensland, Australia. The study also compares parental preferences between RSV immunisation and other early-life vaccinations.

A cross-sectional survey will be conducted among parents who delivered at Wide Bay Hospital and Health Service (WBHHS) facilities between February and November 2024. Eligible participants will be invited via SMS to complete an anonymous online questionnaire hosted on REDCap. A case-control approach will be employed, defining parents who accept RSV immunisation as controls and those who decline as cases, with a 4:1 matching ratio based on demographic characteristics. Statistical analyses, including logistic regression, will identify key predictors of immunisation acceptance.

This study will provide insights into factors shaping parental decisions regarding RSV immunisation, including healthcare provider influence, perceived vaccine safety, and socio-economic determinants. Findings will highlight potential barriers and facilitators, guiding targeted interventions to improve vaccine uptake.

1. Queensland Health Epidemiology: Queensland Acute Respiratory Infection Surveillance Report 2023.
2. Queensland Health Epidemiology: Queensland Acute Respiratory Infection Surveillance Report 2024.

Background
Data on barriers to childhood vaccine uptake are needed alongside coverage data to understand and address declining coverage. In 2024, the National Vaccination Insights project initiated annual surveys to assess the prevalence of access and acceptance barriers to routine childhood vaccination in Australia and determine their associations with under- and non-vaccination.

The 2024 survey found that the most common barrier was feeling distressed when thinking about vaccination, but this was not significantly associated with partial or non-vaccination. Compared to parents of up-to-date children, the partially vaccinated group reported more access barriers like appointment scheduling difficulty and affordability, while acceptance barriers were more associated with non-vaccination. This study will present the data from 2025, compared with previous data to highlight emerging trends.

Methods
This national cross-sectional online survey will be conducted in April 2025. Using an online panel, we will recruit 2000 Australian parents or carers of children aged <5 years who did not participate in the 2024 survey. We will measure 15 access and acceptance barriers to routine childhood vaccine uptake using the validated Vaccine Barriers Assessment Tool. Parents will report their child’s vaccination status (up-to-date, partially vaccinated, or unvaccinated) and demographics. We will calculate prevalence of vaccination barriers and associations between barriers and parent location, financial stress, number of children, and child vaccination status. Comparative analysis with 2024 data will be presented. Data will be weighted using the 2021 estimated resident parent population.

Results
We will present our analysis of the 2025 survey data and a comparison with the data from 2024.

Conclusions
Along with strategies to improve vaccine acceptance, interventions addressing access issues should be prioritised to bring partially vaccinated children up to date. This repeated survey enables comparison over time to inform policy and practice.

Context: Childhood vaccination is a critical public health measure that prevents the spread of infectious diseases. Despite its significance, Australia's childhood vaccination coverage rates have fallen for the third consecutive year, partly due to challenges in delivering actionable insights from the complex Australian Immunisation Register (AIR) data reports, among other factors.

Aim: This project aims to improve childhood vaccination rates in Central and Eastern Sydney PHN (CESPHN) region by leveraging data from AIR to deliver a targeted quality improvement activity for general practices.

Process: The project involves extracting data from the AIR to produce tailored reports for general practices, highlighting children overdue for vaccinations. Framed as a quality improvement (QI) initiative, the project provides clear and actionable guidance for timely follow-ups with parents and guardians. Monthly reports help establish this QI activity as a routine task for the 345 participating general practices.

Analysis: In 2024, the project achieved a 18.46% reduction in children overdue for vaccinations within CESPHN general practices, reducing from 5,200 in January to 4,240 in December. This improvement demonstrates the effectiveness of providing general practices with regular, accessible and actionable reports derived from AIR data to manage overdue childhood vaccinations.

Outcomes: By improving the accessibility and utilisation of vaccination data, this project has not only enabled practices to easily identify and follow-up overdue children but has also driven significant changes in practice behaviour. Embedding data-driven approaches into routine workflows has facilitated a system-wide shift towards proactive immunisation management, ensuring sustainability. These changes contribute to better public health outcomes by reducing the risk of vaccine-preventable diseases among children and strengthening the overall resilience of immunisation programs.

Limitations: A key limitation is the lack of a system to track overdue children to measure intervention and demonstrate an increase in childhood vaccination. This is due to the five-month delay in the release of childhood vaccination coverage data by the Department. Quarterly cohort changes and the absence of practice-specific coverage rates further hinder monitoring progress at the practice level.

Australia has seen a concerning decline in childhood vaccination coverage since the COVID-19 pandemic. Recent research within the National Vaccination Insights Project has found 2 of the 3 most common childhood vaccination barriers reported by parents relate to practical access: lack of affordability and not easy to get a vaccination appointment when due. In addition, significantly more parents living in metropolitan-regional areas reported cost as a vaccination barrier compared with parents living in rural-remote areas.

We present the preliminary findings of a mixed-methods evaluation of a unique initiative aimed at increasing childhood vaccination rates.

For over 20 years, the Central Coast Local Health District (CCLHD) has provided free childhood immunisation drop-in clinics at various locations. The community-based, nurse-led clinics offer a walk-in service, operate across weekdays and Saturdays and are staffed by experienced authorised nurse immunisers from the CCLHD Child and Family Health Service.

Analysis of over 29,000 clinic visits during the past 10 years has found a four-fold increase in service encounters, with growth in both number of individuals and repeat users accessing the service. Saturday clinics saw the highest increase in demand and have been the most popular day since 2022. The proportion of Aboriginal and/or Torres Strait Islander families using the service steadily increased from 2.5% in 2015 to 14.7% in 2024. Those living in the most socio-economically disadvantaged areas of the Central Coast were 1.37 times more likely to use the service than those in the least disadvantaged areas, a trend that has increased over time. These results indicate this type of service has been effective in overcoming some access barriers to vaccination that families experience. Further research is planned to better understand barriers and drivers for service use and where improvements to childhood vaccination coverage on the Central Coast can continue to be made.

The World Health Organization recommends that influenza-vaccine-naïve children <9 years receive two doses, at least one month apart, in the first year of vaccination. This recommendation is based on immunological evidence.
To assess the real-world evidence for this schedule we conducted a systematic review and meta-analysis of studies of influenza vaccine efficacy and effectiveness by dose for children that were previously influenza-vaccine-naïve. To control for intra-seasonal variation, we calculated the pooled absolute difference of directly comparable vaccine efficacy and effectiveness estimates.
Our search of EMBASE, Medline OVID and CINAHL identified 49 papers that met the inclusion criteria. Sixteen papers reported the results of 13 randomised controlled trials (RCTs), 27 were inactivated influenza vaccine (IIV) effectiveness studies and six were monovalent 2009 pandemic effectiveness studies.
All seven of the live attenuated influenza vaccine (LAIV) trials assessed one-dose efficacy and three also assessed two-dose efficacy. Two studies reported directly comparable one and two dose efficacy and the pooled absolute difference between the directly comparable estimates of LAIV efficacy was 10% (95%CI: -1.6% to 21%).
Of the 27 IIV effectiveness studies, 13 were classified as naïve studies (used a population that was previously influenza-vaccine-naïve) and 14 were classified as mixed history studies (only children who received one dose were guaranteed to be previously influenza-vaccine-naïve). Pooled absolute difference between one and two doses of IIV effectiveness from naïve studies was 14%; (95%CI: -3.4% to 31%).
Existing studies are insufficient to assess the additional benefit of a second dose of influenza vaccine in the first year of vaccination. Half the identified VE studies did not adequately control for influenza vaccine history. Further high-quality observational studies or RCTs comparing the impact of one and two doses among influenza-vaccine-naïve children are required to guide immunisation policy.

Maternal immunisation is critical to protect young infants from severe pertussis. However, maternal antibodies may influence how well infants respond to their routine childhood vaccinations (immune interference). There is limited data on whether the number of adult Tdap boosters a woman has received further impacts infant vaccine responses.

We evaluated the immunogenicity, and antibody persistence of immunisations in infants born to mothers who received either their first or second adult Tdap booster during pregnancy. We further examined whether this varied if infants were primed with acellular pertussis (aP1) or whole-cell pertussis (wP1) containing vaccines as their first dose followed by 2 doses of DTaP-IPV-HBV/Hib vaccine at 2-4-6 months of age as part of the Optimum study (ANZCTRN12617000065392p). All infants received 3 doses of 13-valent pneumococcal conjugate vaccine (PCV13) at 2-4-12 months of age and a DTaP-IPV booster at age 18 months.

Serum IgG concentrations specific to diphtheria, tetanus, pertussis, Hib, hepatitis B and PCV13 antigens were measured at ages 6, 7, 18, and 19 months using multiplex fluorescent bead-based immunoassays.

At 6 months, repeat maternal Tdap immunisation was associated with enhanced immune interference in both aP1- and wP1-primed infants. At ages 7 and 18 months, aP-primed infants whose mothers received two Tdap boosters tended to have higher IgG concentrations to some vaccine antigens, however, wP-primed infants whose mothers received two Tdap boosters generally had lower IgG concentrations than those born to mothers who had their first booster. The impact of repeat maternal Tdap was both antigen and temporally dependent.

Our data suggests repeat maternal Tdap immunisation shapes the long-term immune trajectory of infants, and this differs across priming schedules (aP1/ wP1). As fully aP-primed cohorts reach childbearing age, ongoing surveillance is needed to understand the broader implications of repeat maternal Tdap boosting on infant vaccine protection.

Background
Respiratory syncytial virus (RSV) is a major cause of early childhood respiratory illness and hospitalisation, particularly in infants under 6 months of age. In tropical regions, RSV circulates year-round, contrasting with more seasonal peaks in temperate areas. In late 2023, the Australian Therapeutic Goods Administration approved nirsevimab, a long-acting monoclonal antibody for the prevention of severe RSV disease in infants and young children.

Objective
To reduce paediatric RSV hospitalisations through the implementation of a state-wide immunisation program for newborns and other at-risk cohorts.

Methods
A multidisciplinary team developed and implemented the program, considering public health priorities, cost-effectiveness, product availability, clinical recommendations, and state-specific epidemiology. The Queensland Paediatric RSV Prevention Program launched on 15 April 2024, providing free RSV immunisation to eligible infants born on or after 1 February 2024 and for select at-risk cohorts.

Results
There were 406 less RSV-hospitalisations (a 48% reduction) and a 30% reduction in RSV-notifications in infants under 6 months of age since the program commenced (15 April to 31 Dec 2024) compared to the same period in 2023.

Discussion
The implementation of the Queensland Paediatric RSV Prevention Program resulted in a significant reduction in infant RSV hospitalisations for infants under 6 months of age. Key implementation challenges, such as the rapid rollout and timely reporting of birth doses to the Australian Immunisation Register, offered valuable lessons for future public health initiatives. These challenges highlighted the importance of efficient and effective program awareness campaigns and streamlined immunisation data reporting processes. The program's expansion to include maternal RSV vaccination represents a strategic step towards comprehensive newborn protection against severe RSV disease.

Background: Clesrovimab is an investigational, long-acting monoclonal antibody (mAb) targeting site IV of the fusion protein for the prevention of RSV lower respiratory tract infection in infants.

Methods: This phase 2b/3 double-blind, randomized, placebo-controlled pivotal study enrolled healthy preterm and full-term infants birth to 1 year of age entering their first RSV season. Participants (pts) were randomized 2:1 to receive clesrovimab (105 mg IM) or placebo on day 1. Safety and tolerability were a primary endpoint. There were two hypothesis-tested endpoints: the efficacy of clesrovimab against RSV-associated medically attended lower respiratory tract infection (MALRI) through day 150 (primary) and against RSV-associated hospitalization through day 150 (secondary). The MALRI definition required ≥1 indicators of lower respiratory tract infection (LRI) or severity.

Results: There were 3,632 pts randomized across 22 countries; >99% received study intervention. RSV-associated efficacy endpoints through day 150 and day 180. Clesrovimab reduced the incidence of RSV-associated MALRI requiring ≥1 indicator of LRI/severity (60.4% [95% CI: 44.1, 71.9], p<0.001) and ≥2 indicators of LRI/severity (88.0% [95% CI:76.1, 94.0]), RSV hospitalization (84.2% [95% CI: 66.6, 92.6], p<0.001), and severe MALRI (91.7% [95% CI:62.9, 98.1]) through day 150 postdose compared to placebo. Efficacy increased with increasing RSV-associated disease severity and was similar from days 1-180 compared to days 1-150 across endpoints. The proportions of pts with adverse events (AEs), including injection-site and systemic AEs, drug-related AEs, and serious AEs were comparable between the clesrovimab and placebo groups. There were no treatment-related deaths or deaths attributed to RSV disease.

Conclusion: A single dose of clesrovimab given before or during the first RSV season was efficacious in reducing RSV-associated MALRI and RSV-associated hospitalization in healthy preterm and full-term infants and was generally well tolerated with a safety profile comparable to placebo.

Introduction
The RSV immunisation landscape has changed dramatically in recent years with the introduction of both a single-dose monoclonal antibody and a maternal vaccine for the prevention of severe RSV infection in infants. In November 2024, the Australian federal Health Minister announced a hybrid program for 2025, with RSVpreF (maternal vaccine) on the National Immunisation Program, and nirsevimab (monoclonal) to be offered by individual States and Territories. Our aim is to use mathematical modelling to support decision-making around the development of RSV immunisation policy, with an initial focus on Western Australia (WA).

Methods
We developed a dynamic transmission model of RSV calibrated to linked population-based administrative health data from southern WA (cohort data from 2010-2019). The model simulates RSVpreF and nirsevimab immunisation on the population with protection characteristics of the products reflecting efficacy trial data. The model also captures the differential impact of potential immunisation strategies on infants born preterm, a significant subgroup at higher risk of severe RSV infection.

Results
Using our model, we analysed the impact of a set of potential single product and hybrid RSV immunisation scenarios with different assumptions of coverage levels and implementation timing (seasonal versus year-round), and strategies that consider RSV at-risk groups. We show that hybrid strategies combining year-round maternal immunisation with seasonal infant immunisation for newborns and other at-risk subgroups resulted in comparable numbers of averted RSV hospitalisations to high coverage, year-round single product programs. The model predicts the analysed hybrid programs to avert around 50% of annual RSV-hospitalisations of infants under 6 months.

Conclusions
Modelling can provide valuable evidence on the use of alternate RSV immunisation strategies in local or national programs, with consideration to the individual protection characteristics of the prevention products used, and the epidemiology of RSV in the intended population.

In April 2024 the Government of Western Australia commenced a state-funded program to provide infant RSV (respiratory syncytial virus) immunisation, following TGA approval (in November 2023) for use of the immunisation Nirsevimab in Australia. Studies have shown that Nirsevimab provides substantial passive immunity against the infection for at least 5 months after immunisation and is up to 80% effective at preventing RSV associated hospitalisations in infants; its introduction is therefore significant to protecting child health in WA.
Several other jurisdictions around the world rolled out Nirsevimab in 2023; this study engages in a comparative analysis of RSV immunisation communication strategies advanced by governments in Spain, France, Luxembourg, and Australia, comparing materials provided to the public and to healthcare professionals. We aim to understand how messaging relating to RSV immunisation was framed and presented in various countries, specifically through uncovering and comparing the key themes and values expressed in promotional materials. For example, does messaging contain language laden with appeals to specific values held in the community, focus on mitigating parental hesitancy, or adopt a factual, non-emotive approach? By comparing the strategies employed across different national, linguistic, and epidemiological contexts, we provide insight as to how successful strategies and approaches could be translated and tailored to develop communication strategies supporting infant RSV immunisation implementation and uptake (as well as other prospective immunisation programs) in Australia into the future.