Introduction: Seroepidemiology enables the measurement of biomarkers of vaccination or infection with vaccine-preventable diseases (VPDs) and can provide an accurate estimate of population-level immunity compared to vaccination coverage data alone. This study aimed to examine the seroprevalence of VPD immunity and the spatial distribution in Samoa from 2018-2019.

Methods: Dried blood spots (DBS) were collected from two community-based serosurveys of participants aged ≥5 years during the Surveillance and Monitoring to Eliminate Lymphatic Filariasis and Scabies from Samoa (SaMELFS) project. DBS were tested using multiplex bead assays (MBA) to measure the presence of antibodies against diphtheria, measles, rubella, and tetanus. Village-level seroprevalence estimates were adjusted for study design, age, and gender. Spatial analysis was conducted using SatScan.

Preliminary Results: Overall, 6,938 (3,851 in 2018 and 3,087 in 2019) valid MBA results were analysed across 35 villages. The highest seroprevalence estimates were observed for tetanus in 2018 (90.6% [95% Confidence interval (CI):89.3-92.0]) and 2019 (90.9% [95% CI:89.6-92.0]), followed by diphtheria in 2018 (84.5%, [95%CI:83.0-85.9]) and 2019 (81.1% [95%CI:79.4-82.7]) rubella in 2018 (78.7% [95%CI:77-80.3]) and 2019 (79.9% [95%CI:78.1-81.5]), and measles in 2018 (43.7% [95%CI:42.2-45.3] and 2019 (47% [95%CI:45.3-48.7]). Seropositivity to tetanus ranged from 100% seropositivity in Musumusu (2018 and 2019) to 72.9% seropositivity (in 2019) in Utulaelae. Only seven villages had a seropositivity rate over 34% to all four VPDs, and 30 villages had at least one participant seronegative to all VPDs. SatScan identified clusters of low immunity for tetanus (Log likelihood ratio (LLR): 8.5) and measles (LLR: 4.62).

Conclusion: Significant variations in VPD immunity were seen across Samoa in 2018-2019. Considering that measles and rubella vaccines are administered together, the relatively high seroprevalence of rubella compared to measles suggests local transmission of rubella. Identifying clusters of low immunity can inform targeted vaccination strategies to reduce the risk of outbreaks.

The Pacific Public Health Surveillance Network (PPHSN) is a Pacific regional health network that aims to build capacity for infectious diseases surveillance, laboratory testing, hospital infection prevention, and response. It operates through five themed sub-networks. The core objectives of PPHSN include enhancing the capacity of Pacific Member States for effective health surveillance, fostering the development of adequate surveillance systems, harmonising health data needs, and facilitating information sharing and communication within the region.

In March 2019, Pacific Member States requested an external evaluation of PPHSN. This evaluation aimed to examine the purpose, strengths, and limitations of the PPHSN, and its support of Pacific States progress towards International Health Regulation (IHR) 2005 core capacities compliance.

A Pacific-based technical advisory group was established to guide the evaluation. We conducted a document review, administered an online survey and conducted seven focus-groups to examine how PPHSN is meeting its objectives.

Twenty-seven documents were reviewed, 149 PPHSN users responded to the survey and 38 stakeholders were interviewed from across 22 Pacific Member States.
The review found key strengths and weaknesses in PPHSN’s governance, performance, and perceived acceptability and usefulness of the network. The survey highlighted PPHSN’s critical role of facilitating communication (75%; 45/60), timely surveillance (78%; 47/63), and effective capacity building in enhancing outbreak responses (86%; 31/36), while also identifying barriers such as unmodern communication channels (30%; 18/60) and the need for real-time data-sharing improvements (70%;12/42).

PPHSN’s strengths lied in supporting regional communication and coordination of surveillance and outbreak response. It is well aligned to support implementation of IHR2005. However, the network experiences persistent challenges related to governance and funding structures, roles and responsibilities, and stretched public health workforce. Findings will inform the 5-year strategy for PPHSN to support PICTs strengthen outbreak preparedness and response activities.

Covid-19 presented significant challenges worldwide, yet rural communities in Papua New Guinea (PNG) demonstrated resilience, adaptability, and self-reliance in navigating the crisis. Despite resource limitations, communities relied on traditional knowledge, social networks, and localized innovations to manage health risks and food security disruptions. Understanding these lived experiences is essential for developing effective health communication strategies that are responsive to rural realities.
This study was conducted in two rural communities, Balimo, located in Western Province near the Australian border, and Tari, in Hela Province in the Highlands of PNG. It employed a participatory action research approach, using photovoice to document the experiences of sixteen male and female participants. Their narratives provide insight into how rural communities responded to health challenges, adapted pandemic protocols, and sustained their well-being through culturally relevant practices. Findings highlight that while pandemic measures were difficult to implement due to limited access to essential services, communities adapted them to align with their lived realities. Healthcare access, already constrained in remote areas, became a collective effort, with individuals sharing knowledge and resources. Similarly, disruptions to food security prompted a revival of traditional agricultural practices, ensuring sustenance. Traditional healing methods, including steaming, herbal infusions, and the use of medicinal plants, played a crucial role in preventative and curative care.
Rather than focusing solely on vulnerabilities, these findings emphasize the agency and resourcefulness of rural communities. Recognizing and integrating these lived experiences into health communication strategies is crucial for improving crisis preparedness, fostering trust, and ensuring that public health interventions are community-centred, culturally appropriate, and grounded in existing social and knowledge systems.

Background: In East New Britain Province (ENB) Papua New Guinea, 41% of children were considered “zero-dose” (did not receive the first dose of Diphtheria-Tetanus-Pertussis (DTP1) containing vaccine) and 55% were under-immunised (did not receive DTP3) in 2023. This study examined barriers and enablers to routine immunisation in un(der)-vaccinated areas in ENB.

Methods: Face-to-face semi-structured interviews were conducted with caregivers of children aged 12-23 months and healthcare professionals in ENB. Five local research officers conducted the interviews following comprehensive in-country qualitative research training. Data were thematically analysed and mapped across the six UNICEF Journey to Immunisation framework stages. Strategies to address identified immunisation barriers were also discussed.

Results: Thirty-three caregivers and 28 healthcare professionals were interviewed. All caregivers reported that their child had received DTP1, and 91% reported DTP3 vaccination (9% through verbal recall, 12% through record book check and 79% through both). However, they noted barriers including lack of immunisation knowledge, financial and travel challenges, limited availability of healthcare professionals and healthcare professionals not adequately explaining why children should be vaccinated. Vaccination enablers reported by caregivers included support provided by families and accessible services. Barriers reported by healthcare professionals included service delivery costs, non-functioning aid posts and vaccine stock-outs. Healthcare professionals reported that working with community leaders and providing vaccine education sessions facilitated vaccination uptake. Suggested strategies for improving immunisation uptake included developing tailored immunisation communication materials, engaging community members to support routine immunisation promotion activities, and strengthening coordination between communities and healthcare professionals.

Conclusion: Focusing on the identified barriers and enabling factors to implement locally informed strategies for community members and healthcare professionals is critical to increasing childhood routine immunisation coverage. These findings have informed the implementation of interventions including the development of routine immunisation communication materials and community leader and healthcare professional immunisation training.

Background: Immunization coverage varies across Papua New Guinea. In East New Britain (ENB) Province in 2022, only 65.5% and 50.2% of children under one year received their first dose of pentavalent (DTP1) and measles–rubella (MR1) vaccine, respectively. This study aimed to examine barriers and enablers to routine immunization in areas of un(der)-vaccination in ENB. Methods: A face-to-face survey was conducted with caregivers of children aged 12–23 months in ENB. We used Poisson regression to calculate incidence rate ratios (IRR) and 95% confidence intervals (95% CI) for factors associated with timely receipt of DTP1 or MR1 vaccines, defined as a child who was vaccinated between –2 and +30 days of the vaccine schedule. Delayed receipt is defined as a child who was vaccinated >30 days from the recommended due date. Results: Among 237 caregivers surveyed, 59.9% of children were vaccinated within the “timely” window for DTP1 and 34.1% for MR1. Timely DTP1 receipt was associated with a facility-based birth (IRR:1.93; 95% CI: 1.10–3.38) and trusting healthcare workers “very much”, compared to “a little or moderately” (IRR:1.53; 95% CI: 1.17–1.99). For MR1, the caregiver having completed tertiary/vocational education (IRR:1.79; 95% CI: 1.15–2.78), reporting taking a child to be vaccinated is affordable (IRR:1.52; 95% CI: 1.04–2.22), and healthcare workers explaining immunization services and answering associated questions (IRR:1.68; 95% CI: 1.18–2.41) were associated with timely vaccination. Conclusions: Activities to improve timely vaccination in ENB could include strengthening healthcare worker interpersonal communication skills to optimize trust and incentivizing women to give birth in a health facility.

Vanuatu’s population is at risk of neglected tropical diseases (NTDs) and vaccine-preventable diseases (VPDs). Serological surveys that measure the prevalence of antibodies are a strategy for monitoring current or past exposure to infectious pathogens. Integrated serosurveillance using novel multi-bead assays that can detect ~100 different disease-specific antibodies from a single dried blood spot, and has the potential to provide information on the distribution of a wide range of infections, including estimating vaccine coverage.

Between 2021 and 2023, we conducted integrated serological surveys to assess the seroprevalence of IgG antibodies against multiple VPDs, NTDs, and other infectious diseases in 92 villages in Vanuatu’s Tafea, Sanma and Shefa provinces. After obtaining informed consent, approximately 2000 participants aged >1 year of age provided a finger prick blood sample to prepare a dried blood spot (DSB) that was analysed using the Luminex technology. Seroprevalence was defined as the proportion of patients with positive IgG results in DBS specimens.

Here, we report the overall estimated cluster-adjusted seroprevalence in 2048 participants across Tafea (N=467), Sanma (N=624), and Shefa (N=957) for 32 antigens. Of note, the seroprevalence of Chlamydia trachomatis ranged from approximately 35% (95% CI: 21.86–50.29%) in Tafea to 43% (95% CI: 33.75–54.32%) in Shefa; For yaws, seroprevalence of anti-rp17 ranged from 3.52% in Sanma to 16.17% in Tafea across all age groups. The seroprevalence of anti-TmpA ranged from 0.68% in Sanma to 5.67% in Tafea.

Overall, seropositivity of anti-MeV antibodies for measles in children (1-14 years) ranged from 39.45% in Tafea to 50.92% in Shefa, below the reported WHO measles vaccination coverage for 2021-2023. Rubella seroprevalence ranged from 70.38% (95% CI: 52.79–82.92%) in Tafea to 90.33% (95% CI: 81.71–94.84%) in Shefa.

Our results provide a promising measure of effective population-level immunity and exposure to multiple infectious diseases, with the advantage of being cost-effective, scalable, acceptable, and able to target hard-to-reach and high-risk populations. Additional analysis by age groups has been conducted, and comparisons with national immunisation coverage surveys and case reportings is underway.

Background: Vaccine coverage varies significantly across Papua New Guinea (PNG), and is not always accurately reported. Many factors can prevent a vaccinated individual mounting an antibody response protective against infection. We assessed antibodies to five vaccine-preventable diseases - diphtheria, tetanus, pertussis, measles, and rubella – in East New Britain (ENB) province, PNG.

Methods: We collected dried blood spots from children aged 10-23 months to quantify antibody levels using a multi-pathogen serological assay. Vaccination and infection history were also collected for each child.

Results: Across five local-level governments in ENB, 380 blood samples were collected; 378 passed quality control and were included in this analysis. 88% of children had documented evidence of at least one dose of measles-rubella vaccine. Most children had protective levels of antibodies against measles (87.6% >153 IU/mL) and rubella (88.4% >9.36 IU/mL), regardless of vaccination status, and no recent measles or rubella cases were reported in this cohort. Despite 96.8% of children having evidence of least one dose of diphtheria-tetanus-pertussis vaccine, only 72.5% and 42.3% had antibodies above the protective threshold of 0.01IU/mL and 0.1IU/mL for diphtheria and tetanus respectively. Fewer than 5 individuals (<1%) had pertussis antibody levels >30 and <100IU/mL, indicative of protection without recent infection. There were no differences in antibody protection for any antigen by gender.  

Conclusions: Sero-surveillance enables timely monitoring and evaluation of antibodies to vaccine-preventable diseases, facilitating identification of communities at risk of future outbreaks and supporting targeted vaccination campaigns. Although antibodies do not always correlate with protection, most children had high antibodies against measles, rubella, and diphtheria. Children did not have antibodies to pertussis. Comparison of these data with other PNG samples and additional clinical and demographic data will aid interpretation of findings. The ability to integrate other priority pathogens into this assay could enhance timely disease surveillance in PNG.