The value of manual backward contact tracing to control COVID-19 in practice, the Netherlands, February to March 2021: a pilot study.

BackgroundContact tracing has been a key component of COVID-19 outbreak control. Backward contact tracing (BCT) aims to trace the source that infected the index case and, thereafter, the cases infected by the source. Modelling studies have suggested BCT will substantially reduce SARS-CoV-2 transmission in addition to forward contact tracing.AimTo assess the feasibility and impact of adding BCT in practice.MethodsWe identified COVID-19 cases who were already registered in the electronic database between 19 February and 10 March 2021 for routine contact tracing at the Public Health Service (PHS) of Rotterdam-Rijnmond, the Netherlands (pop. 1.3 million). We investigated if, through a structured questionnaire by dedicated contact tracers, we could trace additional sources and cases infected by these sources. Potential sources identified by the index were approached to trace the source's contacts. We evaluated the number of source contacts that could be additionally quarantined.ResultsOf 7,448 COVID-19 cases interviewed in the study period, 47% (n = 3,497) indicated a source that was already registered as a case in the PHS electronic database. A potential, not yet registered source was traced in 13% (n = 979). Backward contact tracing was possible in 62 of 979 cases, from whom an additional 133 potential sources were traced, and four were eligible for tracing of source contacts. Two additional contacts traced had to stay in quarantine for 1 day. No new COVID-19 cases were confirmed.ConclusionsThe addition of manual BCT to control the COVID-19 pandemic did not provide added value in our study setting.

Field Epidemiology: Fit for the future.

In recent years, field epidemiologists have embraced rapidly evolving digital tools, data sources and technologies, and collaborated with an ever-growing field of scientific specialisms. The COVID-19 pandemic put field epidemiology under unprecedented demand and scrutiny. As the COVID-19 emergency recedes, it is timely to reflect on the core values of our profession and the unique challenges and opportunities that lie ahead. In November 2022, alumni of the European Programme for Intervention Epidemiology Training (EPIET) and the European Public Health Microbiology (EUPHEM) training programme celebrated 25 years of EPIET, and the present and future of field epidemiology was discussed. The output was recorded and qualitatively analysed. This Perspective reflects the authors' interpretation of the discussion. We should reaffirm our commitment to field epidemiology's core strengths: competence and rigour in epidemiology, surveillance, outbreak investigation and applied research, leading to timely and actionable evidence for public health. Our future success will be defined by an ability to adapt, collaborate, harness innovation, communicate and, ultimately, by our tangible impact on protecting and improving health.

Field Epidemiology and Public Health Microbiology training: capturing the alumni perspectives of the training's impact.

We present the findings from the European Programme for Intervention Epidemiology Training (EPIET) Alumni Network (EAN) Member Survey conducted in October to December 2021. The EAN consists of field epidemiologists (EPIET) and public health microbiologists (European Public Health Microbiology Training Programme (EUPHEM)) who stay connected after their 2-year fellowship. This active alumni network provides opportunities for career development, mentorship, knowledge exchange and sharing of best practices for community members, affiliated professionals and public health organisations in Europe. Overall, 281 of 732 members participated in the survey. Of the 192 European fellowship alumni respondents, 173 (90%) indicated that skills and competencies acquired during their fellowship improved performance in their role compared with their abilities before the fellowship. Reported skills and competencies that could be further strengthened included data management/analysis, communication, mathematical modelling and leadership/team management. The EAN Member Survey provides valuable feedback to the EAN, as well as the fellowship programme offices at the European Centre for Disease Prevention and Control (ECDC) and affiliated field epidemiology programmes. The COVID-19 pandemic was a stark reminder of how essential cross-border collaborations are for continued European health security. Maintaining and increasing the professional, well-trained workforce remains crucial for optimal response to infectious diseases and protection of public health.

SARS-CoV-2 in lions, gorillas and zookeepers in the Rotterdam Zoo, the Netherlands, a One Health investigation, November 2021.

In November 2021, seven western lowland gorillas and four Asiatic lions were diagnosed with COVID-19 at Rotterdam Zoo. An outbreak investigation was undertaken to determine the source and extent of the outbreak and to identify possible transmission routes. Interviews were conducted with staff to identify human and animal contacts and cases, compliance with personal protective equipment (PPE) and potential transmission routes. Human and animal contacts and other animal species suspected to be susceptible to SARS-CoV-2 were tested for SARS-CoV-2 RNA. Positive samples were subjected to sequencing. All the gorillas and lions that could be tested (3/7 and 2/4, respectively) were RT-PCR positive between 12 November and 10 December 2021. No other animal species were SARS-CoV-2 RNA positive. Forty direct and indirect human contacts were identified. Two direct contacts tested RT-PCR positive 10 days after the first COVID-19 symptoms in animals. The zookeepers' viral genome sequences clustered with those of gorillas and lions. Personal protective equipment compliance was suboptimal at instances. Findings confirm transmission of SARS-CoV-2 among animals and between humans and animals but source and directionality could not be established. Zookeepers were the most likely source and should have periodic PPE training. Sick animals should promptly be tested and isolated/quarantined.

COVID-19 outbreaks among crew on commercial ships at the Port of Rotterdam, the Netherlands, 2020 to 2021.

BackgroundDuring the COVID-19 pandemic, international shipping activity was disrupted as movement of people and goods was restricted. The Port of Rotterdam, the largest port in Europe, remained operational throughout.AimWe describe the burden of COVID-19 among crew on sea-going vessels at the port and recommend improvements in future infectious disease event notification and response at commercial ports.MethodsSuspected COVID-19 cases on sea-going vessels were notified to port authorities and public health (PH) authorities pre-arrival via the Maritime Declaration of Health. We linked data from port and PH information systems between 1 January 2020 and 31 July 2021, derived a notification rate (NR) of COVID-19 events per arrival, and an attack rate (AR) per vessel (confirmed cases). We compared AR by vessel type (workship/tanker/cargo/passenger), during wildtype-, alpha- and delta-dominant calendar periods.ResultsEighty-four COVID-19 events were notified on ships, involving 622 cases. The NR among 45,030 new arrivals was 173 per 100,000 impacting 1% of vessels. Events per week peaked in April 2021 and again in July 2021, when the AR was also highest. Half of all cases were notified on workships, events occurring earlier and more frequently than on other vessels.ConclusionNotification of COVID-19 events on ships occurred infrequently, although case under-ascertainment was likely. Pre-agreed protocols for data-sharing between stakeholders locally and across Europe would facilitate more efficient pandemic response. Public health access to specimens for sequencing and environmental sampling would give greater insight into viral spread on ships.

Introducing a novel "real-time" outbreak alert and notification system to monitor SARS-CoV-2 outbreaks and case fatality in elderly care facilities, the Netherlands, 2020-2022.

Surveillance systems collating individual-level data may limit timely information sharing during rapidly evolving, infectious disease outbreaks. We present a digital outbreak alert and notification system (MUIZ) in which institutional-level data are reported, allowing real-time outbreak monitoring in elderly care facilities (ECF). We describe trends in the number of outbreaks, mean case number per outbreak, and case-fatality rate (deaths/recovered + deaths) of SARS-CoV-2 in ECF notified through MUIZ in the Rotterdam area (April 2020-March 2022). Overall, 369 outbreaks were reported from 128 ECF that registered with MUIZ (approximately 85% of all ECF), and 114 (89%) notified at least one SARS-CoV-2 outbreak. Trends were consistent with the concurrent national epidemiology and societal control measures in place. MUIZ is a simple outbreak surveillance tool that was highly adopted and acceptable to users. Dutch PHS regions are increasingly adopting the system and it has potential for adaptation and further development in similar institutional outbreak settings.

Ongoing rabies outbreak in dogs of unprecedented scale and human cases in Nelson Mandela Bay Municipality, South Africa, up to 13 February 2022.

More than 430 cases of rabies have been confirmed in dogs in the Nelson Mandela Bay Metropolitan Municipality of South Africa since July 2021. We describe the ongoing outbreak, its geographical spread and six related human deaths that have occurred. Further investigation of the outbreak and vaccination of the dog population is required. Raising awareness among healthcare providers, the public, and among international travellers planning to visit the region, is key for action to protect human and animal health.

B Part of It School Leaver Study: A Repeat Cross-Sectional Study to Assess the Impact of Increasing Coverage With Meningococcal B (4CMenB) Vaccine on Carriage of Neisseria meningitidis.

BACKGROUND: Recombinant protein-based vaccines targeting serogroup B meningococci protect against invasive disease but impacts on carriage are uncertain. This study assessed carriage prevalence of disease-associated meningococci in 2018-2020 as the proportion of vaccinated adolescents increased following introduction of a school-based 4CMenB immunization program. METHODS: Eligible participants who completed high school (aged 17-25) in South Australia in the previous year had an oropharyngeal swab taken and completed a risk factor questionnaire. Disease-associated meningococci (genogroups A, B, C, W, X, Y) were detected by meningococcal and genogroup-specific polymerase chain reaction. RESULTS: The analysis included 4104 participants in 2018, 2690 in 2019, and 1338 in 2020. The proportion vaccinated with 4CMenB increased from 43% in 2018, to 78% in 2019, and 76% in 2020. Carriage prevalence of disease-associated meningococci in 2018 was 225/4104 (5.5%). There was little difference between carriage prevalence in 2019 (134/2690, 5.0%; adjusted odds ratio [aOR], 0.82; 95% confidence interval [CI], .64-1.05) and 2020 (68/1338, 5.1%; aOR, 0.82; 95% CI, .57-1.17) compared to 2018. CONCLUSIONS: Increased 4CMenB uptake in adolescents was not associated with decline in carriage of disease-associated meningococci. 4CMenB immunization programs should focus on direct (individual) protection for groups at greatest risk of disease. CLINICAL TRIALS REGISTRATION: NCT03419533.

Gonorrhoea: a systematic review of prevalence reporting globally.

BACKGROUND: The World Health Organization (WHO) recommends periodic gonorrhoea prevalence assessments in the general population or proxies thereof (including pregnant women, women attending family planning clinics, military recruits, and men undergoing employment physicals for example) and in population groups at increased risk, including men-who-have-sex-with-men (MSM) and sex workers. METHOD: We evaluated reported prevalence data, including estimates from proxy general population samples to reflect the WHO recommendations. We describe the outcomes from the general population country-by-country and extend previous reviews to include MSM, sex workers, and extragenital infections. RESULT AND CONCLUSION: In our systematic search, 2015 titles were reviewed (January 2010-April 2019) and 174 full-text publications were included. National, population-based prevalence data were identified in only four countries (the United States of America, the United Kingdom, Peru, New Caledonia) and local population-based estimates were reported in areas within five countries (China, South Africa, Brazil, Benin, and Malawi). The remaining studies identified only reported test positivity from non-probability, proxy general population samples. Due to the diversity of the reviewed studies, detailed comparison across studies was not possible. In MSM, data were identified from 64 studies in 25 countries. Rectal infection rates were generally higher than urogenital or pharyngeal infection rates, where extragenital testing was conducted. Data on sex workers were identified from 41 studies in 23 countries; rates in female sex workers were high. Current prevalence monitoring was shown to be highly suboptimal worldwide. Serial prevalence monitoring of critical epidemiological variables, and guidelines to optimize prevalence study conduct and reporting beyond antenatal settings are recommended.

Intracluster correlation coefficients in a large cluster randomized vaccine trial in schools: Transmission and impact of shared characteristics.

Cluster randomized trials (cRCT) to assess vaccine effectiveness incorporate indirect effects of vaccination, helping to inform vaccination policy. To calculate the sample size for a cRCT, an estimate of the intracluster correlation coefficient (ICC) is required. For infectious diseases, shared characteristics and social mixing behaviours may increase susceptibility and exposure, promote transmission and be a source of clustering. We present ICCs from a school-based cRCT assessing the effectiveness of a meningococcal B vaccine (Bexsero, GlaxoSmithKline) on reducing oropharyngeal carriage of Neisseria meningitidis (Nm) in 34,489 adolescents from 237 schools in South Australia in 2017/2018. We also explore the contribution of shared behaviours and characteristics to these ICCs. The ICC for carriage of disease-causing Nm genogroups (primary outcome) pre-vaccination was 0.004 (95% CI: 0.002, 0.007) and for all Nm was 0.007 (95%CI: 0.004, 0.011). Adjustment for social behaviours and personal characteristics reduced the ICC for carriage of disease-causing and all Nm genogroups by 25% (to 0.003) and 43% (to 0.004), respectively. ICCs are also reported for risk factors here, which may be outcomes in future research. Higher ICCs were observed for susceptibility and/or exposure variables related to Nm carriage (having a cold, spending ≥1 night out socializing or kissing ≥1 person in the previous week). In metropolitan areas, nights out socializing was a highly correlated behaviour. By contrast, smoking was a highly correlated behaviour in rural areas. A practical example to inform future cRCT sample size estimates is provided.

Applying a novel approach to scoping review incorporating artificial intelligence: mapping the natural history of gonorrhoea.

BACKGROUND: Systematic and scoping literature searches are increasingly resource intensive. We present the results of a scoping review which combines the use of a novel artificial-intelligence-(AI)-assisted Medline search tool with two other 'traditional' literature search methods. We illustrate this novel approach with a case study to identify and map the range of conditions (clinical presentations, complications, coinfections and health problems) associated with gonorrhoea infection. METHODS: To fully characterize the range of health outcomes associated with gonorrhoea, we combined a high yield preliminary search with a traditional systematic search, then supplemented with the output of a novel AI-assisted Medline search tool based on natural language processing methods to identify eligible literature. RESULTS: We identified 189 health conditions associated with gonorrhoea infection of which: 53 were identified through the initial 'high yield' search; 99 through the systematic search; and 124 through the AI-assisted search. These were extracted from 107 unique references and 21 International Statistical Classification of Diseases and Related Health Problems Ninth and Tenth Revision (ICD 9/10) or Read codes. Health conditions were mapped to the urogenital tract (n = 86), anorectal tract (n = 6) oropharyngeal tract (n = 5) and the eye (n = 14); and other conditions such as systemic (n = 61) and neonatal conditions (n = 7), psychosocial associations (n = 3), and co-infections (n = 7). The 107 unique references attained a Scottish Intercollegiate Guidelines Network (SIGN) score of ≥2++ (n = 2), 2+ (14 [13%]), 2- (30 [28%]) and 3 (45 [42%]), respectively. The remaining papers (n = 16) were reviews. CONCLUSIONS: Through AI screening of Medline, we captured - titles, abstracts, case reports and case series related to rare but serious health conditions related to gonorrhoea infection. These outcomes might otherwise have been missed during a systematic search. The AI-assisted search provided a useful addition to traditional/manual literature searches especially when rapid results are required in an exploratory setting.

Systematic Literature Review and Quantitative Analysis of Health Problems Associated with Sexually Transmitted Neisseria gonorrhoeae Infection.

OBJECTIVE: Neisseria gonorrhoeae (Ng) is the second most common sexually transmitted bacterial infection (STI), leading to serious health problems in men, women and newborns. While early antibiotic treatment is effective, infections are increasingly antibiotic-resistant. No systematic reviews present health problems associated with Ng infections or their likelihood of occurrence. The objective, therefore, was to conduct a systematic literature review to address these gaps. METHODS: A systematic literature review was conducted of all studies with an English abstract published since 1950 (Pubmed)/1966 (Embase). The search included patients with a history of/current sexually transmitted Ng infection. Expected outcomes were defined from published reviews of gonorrhoea health problems. Observational studies with a control group were included. A decision tree determined the best quality studies for each outcome, prioritising generalisable populations, laboratory-confirmed diagnosis, clearly defined outcomes, no STI co-infections, adjusted analyses and risk estimates. Where feasible, a meta-analysis was performed; otherwise, the best quality study estimates were identified. FINDINGS: In total, 46 studies were included, and 22 health problems were identified. Of these problems, Ng infection was statistically significantly associated with preterm premature ruptures of membranes, preterm birth, low birth weight, stillbirth, infant death, neonatal ophthalmia, schizophrenia in offspring, pelvic inflammatory disease and subsequent tubal infertility, human immunodeficiency virus and prostate cancer/problems. High-quality evidence was generally lacking, with high heterogeneity across studies, and limited or inconclusive data on other health problems. CONCLUSION: Ng infection is associated with severe health problems in women, men and newborns. More high-quality comparative studies are needed to address the limitations in current knowledge.

Modelling the impact of 4CMenB and MenACWY meningococcal combined vaccination strategies including potential 4CMenB cross-protection: An application to England.

Invasive meningococcal disease (IMD), an uncommon but severe disease, affects mainly infants, young children and adolescents. Meningococcal B (4CMenB) and ACWY (MenACWY) vaccines targeting IMD-causing serogroups B and A, C, W and Y, respectively are available for these mostly-affected age-groups. The objective was to assess the impact of 4CMenB and/or MenACWY vaccination strategies on IMD in England, considering MenACWY carriage protection and potential cross-protection of 4CMenB against non-B serogroups. A novel dynamic transmission model was developed, accounting for vaccine characteristics, with separate variables for meningococcal carriage and IMD for three groups: B; ACWY; and 'Other' mostly non-pathogenic serogroups. A dynamic force of infection is assumed for each group. The model analysis uses data from England before 2015 (when 4CMenB and MenACWY were introduced), and accounts for existing MenC vaccination impact. Compared with no vaccination, the smallest decrease in IMD cases is observed for MenACWY strategies (toddler and/or adolescent). 4CMenB (infant or infant/adolescent), alone or with MenACWY, always results in the most rapid and steep decline in IMD cases. Combined strategies with adolescent 4CMenB result in the largest decrease in IMD cases, whereas adding MenACWY for toddlers has a minor impact. With potential 4CMenB cross-protection, 4CMenB infant strategy has a notable impact on reduction of MenW and MenY IMD cases in strategies where MenACWY toddler and/or adolescent vaccination is absent. This novel model allows for analysis of combined 4CMenB and MenACWY strategies including potential 4CMenB cross-protection. In settings comparable to England, a comprehensive meningococcal vaccination programme should include infant 4CMenB as essential building block. Decisions to include MenACWY toddler programmes should consider herd effects of MenACWY adolescent programmes and 4CMenB potential cross-protection effects. Extending 4CMenB infant and MenACWY adolescent programmes with a 4CMenB adolescent programme allows for the largest overall reduction in IMD cases.

Meningococcal B Vaccine and Meningococcal Carriage in Adolescents in Australia.

BACKGROUND: The meningococcal group B vaccine 4CMenB is a new, recombinant protein-based vaccine that is licensed to protect against invasive group B meningococcal disease. However, its role in preventing transmission and, therefore, inducing population (herd) protection is uncertain. METHODS: We used cluster randomization to assign, according to school, students in years 10 to 12 (age, 15 to 18 years) in South Australia to receive 4CMenB vaccination either at baseline (intervention) or at 12 months (control). The primary outcome was oropharyngeal carriage of disease-causing Neisseria meningitidis (group A, B, C, W, X, or Y) in students in years 10 and 11, as identified by polymerase-chain-reaction assays for PorA (encoding porin protein A) and N. meningitidis genogroups. Secondary outcomes included carriage prevalence and acquisition of all N. meningitidis and individual disease-causing genogroups. Risk factors for carriage were assessed at baseline. RESULTS: A total of 237 schools participated. During April through June 2017, a total of 24,269 students in years 10 and 11 and 10,220 students in year 12 were enrolled. At 12 months, there was no difference in the prevalence of carriage of disease-causing N. meningitidis between the vaccination group (2.55%; 326 of 12,746) and the control group (2.52%; 291 of 11,523) (adjusted odds ratio, 1.02; 95% confidence interval [CI], 0.80 to 1.31; P = 0.85). There were no significant differences in the secondary carriage outcomes. At baseline, the risk factors for carriage of disease-causing N. meningitidis included later year of schooling (adjusted odds ratio for year 12 vs. year 10, 2.75; 95% CI, 2.03 to 3.73), current upper respiratory tract infection (adjusted odds ratio, 1.35; 95% CI, 1.12 to 1.63), cigarette smoking (adjusted odds ratio, 1.91; 95% CI, 1.29 to 2.83), water-pipe smoking (adjusted odds ratio, 1.82; 95% CI, 1.30 to 2.54), attending pubs or clubs (adjusted odds ratio, 1.54; 95% CI, 1.28 to 1.86), and intimate kissing (adjusted odds ratio, 1.65; 95% CI, 1.33 to 2.05). No vaccine safety concerns were identified. CONCLUSIONS: Among Australian adolescents, the 4CMenB vaccine had no discernible effect on the carriage of disease-causing meningococci, including group B. (Funded by GlaxoSmithKline; ClinicalTrials.gov number, NCT03089086.).

Meningococcal-group B (MenB) vaccine series completion and adherence to dosing schedule in the United States: A retrospective analysis by vaccine and payer type.

BACKGROUND: Two MenB vaccines with different dosing schedules are approved in the US: MenB-4C (2 doses) and MenB-FHbp (2-3 doses). Both vaccines were licensed on the basis of immunogenicity demonstrated after vaccine series completion. We evaluated vaccination completion and adherence to dosing schedules. METHODS: This retrospective analysis used data from MarketScan Commercial Claims and Encounters Database (Commercial) January 1, 2015 - February 28, 2018 and Multi-State Medicaid Database (Medicaid) January 1, 2015 - December 31, 2017 to examine vaccine series completion and adherence to dosing schedule in individuals who initiated a MenB series at ages 16-23 years. Vaccine series completion and dose schedule adherence were assessed during a 15-month follow-up period after the first dose. Completion was defined as individual receipt of the recommended number of doses, with current recommendations applied retroactively to allow individuals who initiated the MenB-FHbp series to be complete with either the 2- or the 3-dose schedule. RESULTS: The study population comprised 65,205 commercially-insured individuals (36,118 initiated MenB-4C; 29,087 initiated MenB-FHbp) and 13,535 Medicaid-covered individuals (10,153 initiated MenB-4C; 3382 initiated MenB-FHbp). In Commercial, 63% of individuals who initiated MenB-4C and 52% of individuals who initiated MenB-FHbp completed vaccination within 15 months; dosing schedule adherence was 62% for MenB-4C initiators and 18% for MenB-FHbp initiators. In Medicaid, 15-month completion rates for MenB-4C and MenB-FHbp initiators were 49% and 31%, respectively, with corresponding dosing schedule adherence of 48% and 8%. Among individuals who completed the series, median time to completion was 68 days for MenB-4C versus 258 days for MenB-FHbp in Commercial and 88 days for MenB-4C versus 309 days for MenB-FHbp in Medicaid. CONCLUSION: During the study period, MenB vaccine series completion was suboptimal. However, completion was significantly higher for MenB-4C, with notably shorter time to completion. This may reflect the flexible dosing schedule of MenB-4C.

Meningococcal Vaccination Among Adolescents in the United States: A Tale of Two Age Platforms.

PURPOSE: Despite recommended routine vaccination with meningococcal conjugate vaccine (MenACWY) at ages 11-12 years with a booster at age 16 years, national estimates indicate MenACWY uptake is lower in older adolescents than younger adolescents. This study aimed to identify factors associated with MenACWY uptake among adolescents. METHODS: Commercial Claims and Encounters (CCAE) and Medicaid MarketScan Databases from 2011 to 2016 were retrospectively analyzed (2017) to determine receipt of ≥1 dose of MenACWY during early (10.5 through 13 years) and late (15.5 through 18 years) adolescence. Multivariable logistic regression and nonlinear decomposition analyses were used to identify factors associated with MenACWY vaccination, potential missed opportunities, and differences between age groups. RESULTS: A larger proportion of younger adolescents than older adolescents received MenACWY: CCAE, 71.7% versus 48.9% (p < .001); Medicaid, 59.3% versus 31.8% (p < .001), respectively. In multivariable models (CCAE), older adolescents were less likely than younger ones to receive MenACWY (adjusted odds ratios [95% confidence intervals]: .68 [.67, .69]) and more likely to have a potential missed opportunity (1.27 [1.25, 1.28]). Decomposition results showed lower MenACWY uptake in older adolescents is largely attributed to fewer non-MenACWY vaccines received, fewer preventive care visits, and interaction with nonpediatric healthcare providers. DISCUSSION: Missed opportunities and infrequent preventive care encounters contribute to lack of vaccination in younger and older adolescents. However, the disparity in uptake between the two age groups was largely attributable to differences in healthcare utilization, suggesting a need for unique strategies to increase uptake among older adolescents, such as solidifying a vaccination platform for ages 16-18 years through encouragement of annual preventive care visits.

B Part of It School Leaver protocol: an observational repeat cross-sectional study to assess the impact of a meningococcal serogroup B (4CMenB) vaccine programme on carriage of Neisseria meningitidis.

INTRODUCTION: Invasive meningococcal disease is uncommon but associated with a high-case fatality rate. Carriage prevalence of the causative bacteria, Neisseria meningitidis, is high in adolescents. A large (n=34 500) cluster randomised controlled trial (RCT) to assess the impact of a meningococcal B (MenB) vaccine on meningococcal carriage was implemented in the state of South Australia (SA) for year 10, 11 and 12 senior school students in 2017-2018. This study will assess the impact of MenB vaccine (4CMenB) on carriage prevalence in school leavers in SA, 1 and 2 years after implementation of the cluster RCT in adolescents. Measuring the impact of population programmes on carriage can assist in informing future meningococcal immunisation programmes such as targeted age groups and use of catch-up campaigns. METHODS AND ANALYSIS: This repeat cross-sectional study will assess carriage prevalence in 2018 and 2019. All school leavers who attended year 12 in any school in SA in 2018 or 2019 will be invited to participate in this study. An oropharyngeal swab will be taken from each participating student and a risk factor questionnaire completed by the student following informed consent. Students will attend clinics at SA universities, technical colleges, and metropolitan, rural and remote government council clinics. Confirmed vaccination history will allow a comparison in carriage prevalence between vaccinated and unvaccinated school leavers. A sample size of 4096 students per year will provide 80% power to detect a 20% difference in carriage prevalence of disease-causing meningococci (defined as genogroup A, B, C, W, X or Y) between years. ETHICS AND DISSEMINATION: The study was approved by the Women's and Children's Health Network Human Research Ethics Committee. Results will be published in international peer review journals and presented at national and international conferences. TRIAL REGISTRATION NUMBER: NCT03419533; Pre-results.