INTRODUCTION
University of Otago (UoO) has required routine serological screening for measles (Me), mumps (Mu) and rubella (Ru) antibody for the last two decades for entry into health professional courses, irrespective of prior vaccination with measles-containing vaccine (MCV). Students seronegative for Me, Mu, or Ru received MMR vaccine. We examined patterns of seronegativity among UoO health professional students between 2015-2020.

METHODS
Ethical approval was obtained for analysis of de-identified pre-enrolment data on seroprevalence to Me, Mu, and Ru based on thresholds from the Trinity test. Odds ratios (ORs) were calculated for the following predictor variables of seronegativity by logistic regression: residency status (international vs domestic), age, gender, MCV status (from records or declaration), and for domestic students: ethnicity (European, Māori, Pacific, and Asian/Other).

RESULTS
Of 4,479 students, 4,408 (98.4%) had complete data (median age: 19 years; 63.0% female; 90.5% MMR2, 90.0% domestic). 963 were measles seronegative (21.9%; 95% CI: 20.7, 23.1); 3.6-fold greater in 331 (34.4%) seronegative to Mu and Ru (171; 51.7%) than 3,017 seropositive to both (438; 14.5%). Seronegativity was similar in 3,001 (68.1%) with MCV2 verified by records (20.8%) and 953 by declaration (23.3%). Seronegativity predictors (multivariate): age <30 years (OR: 1.7, 95% CI: 1.0, 2.8); male (OR: 1.3; 95% CI 1.2, 1.5); international student (OR: 1.4; 95% CI: 1.1, 1.7); among domestic students: Pacific (OR: 2.0; 95% CI: 1.4, 2.9) and Asian or other ethnicity (OR: 1.7; 95% CI: 1.5, 2.1); presumptive non-NZ born (international and domestic Pacific, Asian/other) vs European or Māori (OR: 1.8; 95% CI: 1.5, 2.0).

CONCLUSION
Measles seronegativity was common in health professional students with vaccine-acquired immunity, significantly lower with age >30 years and significantly higher in males, if seronegative to Mu and Ru, and with presumptive vaccination outside NZ.

Commonly carried harmlessly in the nasopharynx, Streptococcus pneumoniae is a multi-serotype pathogen that causes a substantial global burden of invasive pneumococcal disease and community acquired pneumonia. Almost 100 serotypes have been identified, with multiple circulating serotypes competing for host resources in the same population. Pneumococcal conjugate vaccines have been implemented worldwide, protecting against colonisation and disease with selected high-burden serotypes, but in many settings, short-term effectiveness has been eroded by serotype replacement. Vaccines with broader serotype coverage have been developed, at the cost of immunogenicity against single serotypes. To determine the longer-term impact of these new formulations, we propose a novel modelling framework that evaluates the relationship between serotype-specific vaccine immunogenicity and effectiveness, comprising immunity, carriage and clinical models. Dynamics of individual serotypes are modelled over time, including between-serotype competition and heterogeneity of immunogenicity, advancing existing paradigms that group all serotypes according to vaccine type. This modelling framework is sufficiently flexible to consider diverse populations and vaccine implementation strategies. A retrospective analysis of sequential introduction of 7- and 13-valent pneumococcal conjugate vaccines in Australia validates and demonstrates the model.

Introduction
In response to concerns regarding breakthrough episodes of vaccine-type invasive pneumococcal disease (VT-IPD) in those fully vaccinated, the Australian infant 13-valent pneumococcal conjugate vaccine (PCV13) program transitioned from a 3+0 (implemented in July-2011) to a 2+1 schedule in July-2018. This study aimed to assess the impact of this schedule change on IPD epidemiology in children and estimate the vaccine effectiveness (VE) of the 2+1 schedule compared to 3+0 against IPD using a matched case-control approach.

Methods
We analysed all IPD notifications (cases) to the National Notifiable Disease Surveillance System between July 2011 to September 2024, among children born from 01 May 2011 (age-eligible to have received PCV13). For VE analysis, controls (matched by age, First Nations status and jurisdiction) were extracted from the Australian Immunisation Register.

Results
The study period included 3654 notified IPD cases; approximately half (n=1861) were among children aged <24 months. Of these, 74% (n=1375/1861) had at least one serotype identified, of which 34% (n=471/1375) were a PCV13-VT. The proportion of IPD due to VT-IPD in these children decreased from 43% in 2013 to 22% in 2023 (relative risk [RR]:0.51;95% confidence interval [CI]:0.35,0.75), and ST-3 replaced ST-19A as the predominant VT-ST (17% and 55% in 2013 to 59% and 18% in 2023, respectively). The most common clinical phenotype among those aged <24 months was bacteraemia (42%, n=779), followed by bacteraemic pneumonia (26%; n=481) and meningitis (12%; n=214); the proportion of meningitis was lower in the 2+1 cohort compared to 3+0 cohort (RR:0.48;95% CI:0.36,0.64). Of the 3348 cases included in the VE analysis, 11% (n=351) were unvaccinated prior to IPD onset; 5% of controls were unvaccinated. VE analysis is ongoing.

Conclusions
Our study provides valuable insights into the impact of the 2+1 schedule on the burden and epidemiology of VT-IPD. VE results will be finalised and presented at the conference.

Introduction
In pre-licensure trials, 13 valent Pneumococcal Conjugate Vaccine (13vPCV) elicited lower immune responses against serotype 3 (ST3). In post-licensure studies, IPD due to ST3 has continued to occur in fully-vaccinated children. We explored changes in ST3 disease epidemiology since the introduction of 13vPCV to Australia’s National Immunisation Program.
Methods
We identified all IPD cases caused by ST3 from the National Notifiable Disease Surveillance System from 1 January 2012 to 31 December 2023. The clinical profile of ST3 IPD cases, and trends comparing the early 13vPCV implementation period (2012–2014) to two recent years (2022–2023) were assessed using relevant proportions, age-specific IPD incidence rates and incidence rate ratios (IRR) with 95% confidence interval (CI).
Results
Overall ST3 accounted for 12% of all IPD cases (n=2,586/20,841) and 17% (n=262/1,591) of IPD-related deaths. The proportion was higher in 2022-23 (23% child, 14% adults IPD cases). The most common clinical presentation was pneumonia (79% of total ST3 IPD cases in children <5 years, 75% in adults ≥65 years), with 37% of paediatric ST3 IPD cases complicated by empyema or pleural effusion. Overall, ST3 meningitis was rare (4%, of total ST3 IPD cases). From 2012 to 2023, ST3 IPD incidence rose from 0.8 to 4.0/100,000 (children), and 2.2 to 2.6/100,000 (adults); resulting in IRRs (2022-23 vs. 2012-14) of 3.5 (95% CI: 2.5-4.9) in children <5 years, 7.5 (95% CI: 4.2-14.3) in children 5-14 years, and 1.2 (95% CI: 0.9 to 1.5) in adults.
Conclusion
Since the introduction of 13vPCV, the progressive rise in the incidence of ST3 IPD highlights a key ongoing challenge for pneumococcal disease prevention. Immune responses against ST3 in newer generation PCVs vary, and clinical effectiveness remains uncertain. Efforts need to continue to gain further understanding of ST3 IPD. including genomic analyses and the development of new vaccine technologies to improve IPD prevention.

Background
Despite pneumococcal conjugate vaccine (PCV) introduction and high uptake, First Nations children in remote northern Australia have a high prevalence of pneumococcal carriage and serotype diversity, beginning early in life. Non-vaccine serotypes dominate, and rates of all-cause otitis media persist from a very young age. Currently, the 13-valent PCV, Prevnar13 (PCV13) is used in a 3+1 series at 6 weeks, and 4, 6, and 12 months. Three PCV’s- PCV15, PCV20 and PCV21, are potentially entering the Australian market.
Methods
Using nasopharyngeal carriage, serotype and antimicrobial resistance data from 2013 – 2019 during a pneumococcal vaccine trial, the potential impact of increasing valency vaccines on serotype-specific carriage and resistance will be estimated (% carried serotypes included).
Results
The estimated change in proportion of carried and resistant serotypes potentially impacted by additional serotypes in PCV15, 20 and 21 will be reported by age and pre- and post- each primary and booster dose.
Conclusions
The current serotype population is dominated by non-PCV13 serotypes, the potential of higher valency vaccines to reduce disease will be estimated and described. This data is the only pneumococcal carriage data available to inform vaccine policy in Australia.

Background:

Japanese Encephalitis (JE) is a mosquito-borne disease of concern, with high case-fatality rates and significant long-term effects on survivors. In addition to preventing mosquito bites, vaccination is the most effective prevention method, but global uptake is limited. This study aims to systematically review global research on knowledge, attitudes, and practices (KAP) towards JE vaccination and identify barriers to effective program delivery.

Methods:

We searched seven data bases, reference lists of included studies and grey literature for studies on KAP for JE vaccination. Studies were screened by a minimum of two independent reviewers, resolving discrepancies by consensus. The data were then thematically summarised using the American Psychological Associations (APA) definitions of Knowledge, Attitudes and behavior to benchmark our synthesis.

Results:

Of the 2452 records, 26 studies from seven countries met the inclusion criteria. Studies were of variable quality and inconsistent in how KAP were measured and reported. Studies examined four participants groups: vaccine recipients (travellers, caregivers and non-traveller adults), and vaccine providers/advocates. Of the few studies that reported knowledge, travellers and adult groups had little to no knowledge of the vaccine, whereas caregivers had knowledge about the availability gained through health workers and community leaders. Higher literacy among caregivers, non-traveller adults and vaccine advocates was associated with increased vaccine uptake. Most studies reported only attitudes and practices. Attitudes were generally positive and influenced by health worker and community leaders. Practices among travellers were driven by cost and time. Cost, migration and vaccine availability drove practices among caregivers and non-traveller adults living in endemic countries.

Conclusion:

There is limited information on knowledge, attitudes, and practices (KAP) regarding Japanese Encephalitis (JE) vaccination in both endemic and non-endemic countries. Engaging community leaders and healthcare providers/advocates, and tailoring interventions for different population groups can help address barriers to JE vaccination and improve uptake.

Background
Timor-Leste has declared elimination of measles and rubella. A nationally representative serosurvey in 2022 identified a measles immunity gap (IgG seroprevalence 59.6% in those aged <5 years). The Timor-Leste Ministry of Health responded with a Supplementary Immunisation Activity (SIA) in March 2023, which aimed to provide Measles Rubella (MR) vaccination (one dose) to all children aged <5 years. This study aimed to measure the impact of the SIA on measles and rubella seroprevalence in five municipalities in Timor-Leste.

Methods
5/13 municipalities were chosen to represent different geographic regions of Timor-Leste, and around 600 children aged <10 years who had participated in the baseline survey were eligible. The original selection of participants was based on a three-stage cluster random sample of census-enumerated households. Serum was tested for measles IgG (Euroimmun enzyme-linked immunosorbent assay (ELISA)) and rubella IgG (VITROS immunoassay) in the National Health Laboratory. Seropositivity was calculated using cut-off value of >=120IU/L for measles and IgG≥10IU/L for rubella. Data regarding routine childhood immunisation and SIA participation were collected.

Results
434/486 (89%) eligible children participated. Among those who were SIA-eligible (aged <5 years at time of SIA), 32/103 (31.1%) received ‘validated doses’; 29/103 (28.2%) received ‘non-validated doses’ (‘crude uptake’ 59.3%); 42/103 (40.8%) did not receive a dose. MR SIA uptake was higher in previously vaccinated individuals (58/88, 65.9%) compared to unvaccinated children 3/15, 20.0%; p=0.0013). Measles seropositivity increased from 41.9% to 47.5%; rubella seropositivity did not significantly increase (85.0% to 86.2%). Of those who were measles seronegative at baseline, 10/15 (66.7%) became seropositive after a validated SIA dose. Reasons for non-participation in the MR SIA included being unaware of the campaign (24/42, 57.1%) and being too busy (5/42, 11.9%).

Conclusions
The SIA achieved modest improvement in measles seroprevalence in eligible children in Timor-Leste, where there is an ongoing immunity gap and associated risk of measles transmission. Effective strategies are needed to improve immunisation coverage.

The availability and use of biological and small molecule targeted therapies are rapidly expanding. The intricate nature of their mechanisms of action and the impact of the underlying condition makes it challenging for clinicians to understand the infectious complication risks and safety/efficacy of vaccination for individuals prescribed these agents. We aimed to summarise the current evidence via structured literature searches, focusing on the risk of vaccine-preventable diseases, vaccine efficacy and safety in patients receiving these novel therapies.

Our review revealed the dysregulated immunity, infection risk and vaccine responses in patients on biological and small molecule agents varied widely, ranging from high (e.g., alemtuzumab, blinatumomab) to negligible (e.g., etanercept, mepolizumab, imatinib). The observed infectious complications may differ from what would be predicted based on the mechanism of action, possibly due to a cohesive interplay of the innate and adaptive immune response to infection. Higher risks of serious infection were associated with the receipt of concomitant immunosuppressive medications, particularly corticosteroids. Current immunogenicity data is limited in assessing humoral responses from patients treated with biological therapies and are predominately investigating COVID-19, influenza, and pneumococcal vaccines, with fewer on herpes zoster, hepatitis B, and diphtheria/tetanus vaccines. Evidence suggests that the use of biological therapies results in attenuation, but not abolishment, of the antibody response to vaccines. Despite safety being a concern for live vaccines administered to patients prescribed biological agents, very few vaccine-strain infections in children have been reported, with most involving varicella vaccines, not vaccine-derived measles or rubella.

Current evidence is largely based on non-randomised trials and observational studies. Including immunocompromised individuals in future trials is necessary for accurate evaluation with assessments of cellular response, clinical efficacy and safety. Better prediction models or biomarkers for stratifying risk and predicting vaccine efficacy are important further steps.

Background: A dramatic rise in pertussis cases was observed globally in 2023–2024. In Queensland cases in 2024 rose to the highest value since becoming notifiable. Pertussis epidemics occur every 3–4 years, influenced by waning immunity from acellular vaccine. Here we describe the epidemiology of pertussis in Queensland in 2024.

Methods: We extracted pertussis notifications of Queensland residents from 1991 to 2024, inclusive. Case counts and rates in 2024, overall and in specific age-groups, were compared with the 10-year mean incidence rates (2014–2023) and 2011 (previous annual peak).

Results: The total number of pertussis cases for 2024 (14,986) was more than 12 times higher than the 10-year mean (1,187 cases/year) and 67% higher than 2011 (8,985). Age-group specific incidence rates in 2024 were observed to peak at 10–14-years (1,300/100,000 persons) with those aged 10-, 11- and 12-years accounting for 25% of all cases, with those aged 13 years representing 3% of all cases.
Infants aged <6 months represented 1% of cases in 2024 with an incidence rate (403/100,000 persons), 6.9 times higher compared with the 10-year mean (58/100,000 persons) though 14% lower than 2011 (469/100,000 persons). In 2024, the incidence rate for infants aged <6 months was 61% and 69% lower than the 5–9 year and 10–14-year-old age groups, respectively. Maternal vaccination was given in pregnancy for 48% of cases aged <6 months.

Conclusion: We found overall and age-group specific rates are congruent with what is known about pertussis in the vaccine era, the vaccination schedule and waning immunity. Despite unprecedented case numbers overall, rates in infants were lower than older children and adolescents in 2024. The known protective benefit of the maternal vaccination and demonstration of the effect of the adolescent booster suggest the value of targeting these age-groups, particularly during pertussis epidemics.

Introduction
Adults ≥50 years are recommended to receive a diphtheria-tetanus-pertussis (dTp) booster if their last vaccine was >10 years ago, but recorded uptake among older Australians is low (30% for diphtheria and 20% for pertussis on the Australian Immunisation Register [AIR]), and the vaccine is not funded by the National Immunisation Program. This is despite most tetanus deaths occuring in adults ≥65 years and in 2024 Australia experiencing the highest ever pertussis cases on record. As immunisation data are incomplete and seroprevalence data outdated, this study aimed to estimate the prevalence of antibodies to diphtheria, tetanus and pertussis in adult blood donors.

Methods
Stored de-identified residual whole blood samples from blood donors aged ≥18 years were collected as part of a 2022 serosurvey for SARS-CoV-2 (COVID-19) (n = 21,000) and 1,945 were randomly selected for this study. A total of 1,881 were tested using commercial Virion enzyme immunoassays (IgG) to pertussis, diphtheria, and tetanus toxin. Results were analysed in the following age cohorts: 18-34 years, 35-49 years, 50-64 years, 65-74 years, 75-85 years.

Results
Of the tested samples, 1407 (74.8%) donors were born in Australia and 1,097 (58.3%) were male. Preliminary data indicates that 120 (6.4%) donors had diphtheria antibody levels (≥1.0 IU/mL), 1817 (96.6%) donors had tetanus antibody levels (≥0.1 IU/mL) and 1249 (66.4%) donors had pertussis antibody (XX) levels >5 IU/mL. Further analysis is underway and more results will be presented.

Conclusion
Detailed data on antibody seroprevalence in older donors compared to younger blood donors, will provide essential information to assess population immunity gaps against these three pathogens and inform the need for targeted strategies to promote vaccination in older Australians.

Background
A six-in-one vaccine that combines pentavalent vaccine (diphtheria, tetanus, whole-cell pertussis [DTwP], hepatitis B and Haemophilus influenzae type b) with inactivated polio vaccine (IPV) was prequalified by WHO in March 2024. The Solomon Islands currently offers OPV & Pentavalent vaccine at 6,10 & 14 weeks with a single IPV at 14 weeks and two doses of Measles Rubella at 12 and 18 months. In order to align with WHO recommendations a second dose of IPV and a booster for DTPw should be included. Solomon Islands is one of eight bOPV-using countries in the Pacific that are yet to introduce IPV2 into the immunization program.
Methods
A Hexavalent Switch three-day Workshop was conducted in Honiara in August 2024 with lead staff from Solomon Islands EPI, Finance, Public Health & Paediatrics with country based staff and visiting experts from NCIRS, WHO, World Bank & UNICEF to optimize the immunization schedule and align with WHO recommendations. The workshop considered a range of implications in schedule changes including impact on the community, the EPI Program, HR and logistics; as well as polio risk and the supply and cost of the Hexavalent vaccine.
Results
The workshop determined that Solomon Islands is not eligible to switch to an IPV-only regime as it is at medium risk of polio reintroduction, the routine immunization coverage of DTP3 is < 90% and it has not yet introduced the 2nd IPV dose.
While the use of the Hexavalent vaccine would result in 2 less injections for the child, there were concerns with duplication in the presence of continuing bOPV vaccine and the additional cost
Conclusion
The preferred option for Solomon Islands at this time was to optimize the current schedule with the addition of a second dose of IPV with MR1 and introduction of DTP booster with MR2. This would align with WHO recommendations. It is also the cheapest option. There is sufficient capacity in the current cold chain network. Hexavalent vaccine is planned to be reconsidered in time with the oral polio vaccine cessation likely in 2030 with the polio endgame strategy.