Good or best practice statements: proposal for the operationalisation and implementation of GRADE guidance.

An evidence-based approach is considered the gold standard for health decision-making. Sometimes, a guideline panel might judge the certainty that the desirable effects of an intervention clearly outweigh its undesirable effects as high, but the body of supportive evidence is indirect. In such cases, the application of the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach for grading the strength of recommendations is inappropriate. Instead, the GRADE Working Group has recommended developing ungraded best or good practice statement (GPS) and developed guidance under which circumsances they would be appropriate.Through an evaluation of COVID-1- related recommendations on the eCOVID Recommendation Map (COVID-19.recmap.org), we found that recommendations qualifying a GPS were widespread. However, guideline developers failed to label them as GPS or transparently report justifications for their development. We identified ways to improve and facilitate the operationalisation and implementation of the GRADE guidance for GPS.Herein, we propose a structured process for the development of GPSs that includes applying a sequential order for the GRADE guidance for developing GPS. This operationalisation considers relevant evidence-to-decision criteria when assessing the net consequences of implementing the statement, and reporting information supporting judgments for each criterion. We also propose a standardised table to facilitate the identification of GPS and reporting of their development. This operationalised guidance, if endorsed by guideline developers, may palliate some of the shortcomings identified. Our proposal may also inform future updates of the GRADE guidance for GPS.

The BIGG-REC database makes available all WHO/PAHO evidence informed recommendations.

OBJECTIVE: To build and maintain a living database of the Pan American Health Organization/World Health Organization (PAHO/WHO) recommendations developed using GRADE. STUDY DESIGN AND SETTING: Guidelines are identified from WHO and PAHO databases. We periodically extract recommendations, according to the health and wellbeing targets of Sustainable Development Goal 3. RESULTS: As of March 2022, the BIGG-REC (https://bigg-rec.bvsalud.org/en) database hosted 2682 recommendations contained in 285 WHO/PAHO guidelines. Recommendations were classified as follows: communicable diseases (1,581), children's health (1,182), universal health (1,171), sexual and reproductive health (910), non-communicable diseases (677), maternal health (654), COVID-19 (224), use of psychoactive substances (99), tobacco (14) and road and traffic accidents (16). BIGG-REC allows searching by SDG-3, condition or disease, type of intervention, institution, year of publication and age. CONCLUSION: Recommendation maps provide an important resource for health professionals, organizations and Member States that use evidence-informed guidance to make better decisions, providing a source for the adoption or adaptation of recommendations to meet their needs. This one-stop shop database of evidence-informed recommendations built with intuitive functionalities undoubtedly represents a long-needed tool for decision-makers, guideline developers and the public at large.

The life and death of living systematic reviews: a methodological survey.

OBJECTIVES: The objectives of this study are to describe the characteristics of living systematic reviews (LSRs) and to understand their life cycles. STUDY DESIGN AND SETTING: We conducted a comprehensive search up to April 2021 then selected articles and abstracted data in duplicate and independently. We undertook descriptive analyses and calculated delay in version update and delay since the last published version. RESULTS: We included 76 eligible LSRs with a total of 279 eligible versions. The majority of LSRs was from the clinical field (70%), was COVID-19 related (63%), and had a funding source specified (62%). The median number of versions per LSR was 2 (interquartile range (IQR) 1-4; range 1-19). The median and IQR for the ratio of the actual period of update to the planned period of update was 1.12 (0.81; 1.71). Out of all reviews with a 'planned period of update' and at least one update (N = 19), eight LSRs (42%) had a period since last published version greater than 3 times the planned period of update. No LSR included a 'retirement notice' in their latest published version. CONCLUSION: While most LSR complied with the planned period of producing updates, a substantive proportion lagged since their last update.

Knowledge mobilization activities to support decision-making by youth, parents, and adults using a systematic and living map of evidence and recommendations on COVID-19: protocol for three randomized controlled trials and qualitative user-experience studies.

INTRODUCTION: The COVID-19 pandemic underlined that guidelines and recommendations must be made more accessible and more understandable to the general public to improve health outcomes. The objective of this study is to evaluate, quantify, and compare the public's understanding, usability, satisfaction, intention to implement, and preference for different ways of presenting COVID-19 health recommendations derived from the COVID-19 Living Map of Recommendations and Gateway to Contextualization (RecMap). METHODS AND ANALYSIS: This is a protocol for a multi-method study. Through an online survey, we will conduct pragmatic allocation-concealed, blinded superiority randomized controlled trials (RCTs) in three populations to test alternative formats of presenting health recommendations: adults, parents, and youth, with at least 240 participants in each population. Prior to initiating the RCT, our interventions will have been refined with relevant stakeholder input. The intervention arm will receive a plain language recommendation (PLR) format while the control arm will receive the corresponding original recommendation format as originally published by the guideline organizations (standard language version). Our primary outcome is understanding, and our secondary outcomes are accessibility and usability, satisfaction, intended behavior, and preference for the recommendation formats. Each population's results will be analyzed separately. However, we are planning a meta-analysis of the results across populations. At the end of each survey, participants will be invited to participate in an optional one-on-one, virtual semi-structured interview to explore their user experience. All interviews will be transcribed and analyzed using the principles of thematic analysis and a hybrid inductive and deductive approach. ETHICS AND DISSEMINATION: Through Clinical Trials Ontario, the Hamilton Integrated Research Ethics Board has reviewed and approved this protocol (Project ID: 3856). The University of Alberta has approved the parent portion of the trial (Project ID:00114894). Findings from this study will be disseminated through open-access publications in peer-reviewed journals and using social media. TRIAL REGISTRATION: Clinicaltrials.gov NCT05358990 . Registered on May 3, 2022.

Ventilation Techniques and Risk for Transmission of Coronavirus Disease, Including COVID-19: A Living Systematic Review of Multiple Streams of Evidence.

BACKGROUND: Mechanical ventilation is used to treat respiratory failure in coronavirus disease 2019 (COVID-19). PURPOSE: To review multiple streams of evidence regarding the benefits and harms of ventilation techniques for coronavirus infections, including that causing COVID-19. DATA SOURCES: 21 standard, World Health Organization-specific and COVID-19-specific databases, without language restrictions, until 1 May 2020. STUDY SELECTION: Studies of any design and language comparing different oxygenation approaches in patients with coronavirus infections, including severe acute respiratory syndrome (SARS) or Middle East respiratory syndrome (MERS), or with hypoxemic respiratory failure. Animal, mechanistic, laboratory, and preclinical evidence was gathered regarding aerosol dispersion of coronavirus. Studies evaluating risk for virus transmission to health care workers from aerosol-generating procedures (AGPs) were included. DATA EXTRACTION: Independent and duplicate screening, data abstraction, and risk-of-bias assessment (GRADE for certainty of evidence and AMSTAR 2 for included systematic reviews). DATA SYNTHESIS: 123 studies were eligible (45 on COVID-19, 70 on SARS, 8 on MERS), but only 5 studies (1 on COVID-19, 3 on SARS, 1 on MERS) adjusted for important confounders. A study in hospitalized patients with COVID-19 reported slightly higher mortality with noninvasive ventilation (NIV) than with invasive mechanical ventilation (IMV), but 2 opposing studies, 1 in patients with MERS and 1 in patients with SARS, suggest a reduction in mortality with NIV (very-low-certainty evidence). Two studies in patients with SARS report a reduction in mortality with NIV compared with no mechanical ventilation (low-certainty evidence). Two systematic reviews suggest a large reduction in mortality with NIV compared with conventional oxygen therapy. Other included studies suggest increased odds of transmission from AGPs. LIMITATION: Direct studies in COVID-19 are limited and poorly reported. CONCLUSION: Indirect and low-certainty evidence suggests that use of NIV, similar to IMV, probably reduces mortality but may increase the risk for transmission of COVID-19 to health care workers. PRIMARY FUNDING SOURCE: World Health Organization. (PROSPERO: CRD42020178187).

Using Explicit Thresholds were valuable for judging Benefits and Harms in partially contextualized GRADE Guidelines.

OBJECTIVES: Guideline panels must assess the magnitude of health benefits and harms to develop sensible recommendations. However, they rarely use explicit thresholds. In this paper we report on the piloting and the use thresholds for benefits and harms. STUDY DESIGN AND SETTING: We piloted the use of thresholds in a Chilean COVID-19 living guideline. For each of the critical outcomes, we asked panelists to suggest values of the thresholds for large, moderate, small, or trivial or no effect. We collected this information through a survey and an on-line discussion. RESULTS: Twelve panelists decided on thresholds for three critical outcomes (mortality, need for mechanical ventilation and serious adverse events). For all outcomes, an absolute risk reduction was considered larger with more than 50 events, moderate with less than 50 events, small with less than 25 events, and trivial with less than 10 events. Having these a priori thresholds in place significantly impacted on the development of recommendations. CONCLUSION: Explicit thresholds were a valuable addition to the judgment of the certainty in the evidence, to decide the direction and strength of the recommendation and to evaluate the need for update. We believe this is a line of research worth perusing.

Identifying Health Equity Factors That Influence the Public's Perception of COVID-19 Health Information and Recommendations: A Scoping Review.

The COVID-19 pandemic has impacted global public health and public trust in health recommendations. Trust in health information may waver in the context of health inequities. The objective of this scoping review is to map evidence on public perceptions of COVID-19 prevention information using the PROGRESS-Plus health equity framework. We systematically searched the MEDLINE, Cochrane Central Register of Controlled Trials, PsycInfo, and Embase databases from January 2020 to July 2021. We identified 792 citations and 31 studies published in 15 countries that met all inclusion criteria. The majority (30/31; 96.7%) of the studies used an observational design (74.2% cross-sectional, 16.1% cohort, 6.5% case study, 3.2% experimental trials). Most studies (61.3%) reported on perception, understanding, and uptake, and 35.5% reported on engagement, compliance, and adherence to COVID-19 measures. The most frequently reported sources of COVID-related information were social media, TV, news (newspapers/news websites), and government sources. We identified five important equity factors related to public trust and uptake of recommendations: education and health literacy (19 studies; 61.3%), gender (15 studies; 48.4%), age (15 studies; 48.4%), socioeconomic status (11 studies; 35.5%), and place of residence (10 studies; 32.3%). Our review suggests that equity factors play a role in public perception of COVID-19 information and recommendations. A future systematic review could be conducted to estimate the impact of equity factors on perception and behavior outcomes.

An evaluation of the COVID-19 recommendation map identified diverging clinical and public health guidance.

OBJECTIVES: To describe divergence between actionable statements issued by coronavirus disease 2019 (COVID-19) guideline developers cataloged on the "COVID-19 Recommendations and Gateway to Contextualization" platform. STUDY DESIGN AND SETTING: We defined divergence as at least two comparable actionable statements with different explicit judgments of strength, direction, or subgroup consideration of the population or intervention. We applied a content analysis to compare guideline development methods for a sample of diverging statements and to evaluate factors associated with divergence. RESULTS: Of the 138 guidelines evaluated, 85 (62%) contained at least one statement that diverged from another guideline. We identified 223 diverging statements in these 85 guidelines. We grouped statements into 66 clusters. Each cluster addressed the same population, intervention, and comparator group or just similar interventions. Clinical practice statements were more likely to diverge in an explicit judgment of strength or direction compared to public health statements. Statements were more likely to diverge in strength than direction. The date of publication, used evidence, interpretation of evidence, and contextualization considerations were associated with divergence. CONCLUSION: More than half of the assessed guidelines issued at least one diverging statement. This study helps in understanding the types of differences between guidelines issuing comparable statements and factors associated with their divergence.

American Society of Hematology living guidelines on the use of anticoagulation for thromboprophylaxis in patients with COVID-19: January 2022 update on the use of therapeutic-intensity anticoagulation in acutely ill patients.

BACKGROUND: COVID-19-related acute illness is associated with an increased risk of venous thromboembolism (VTE). OBJECTIVE: These evidence-based guidelines from the American Society of Hematology (ASH) are intended to support patients, clinicians, and other health care professionals in making decisions about the use of anticoagulation in patients with COVID-19. METHODS: ASH formed a multidisciplinary guideline panel that included patient representatives and applied strategies to minimize potential bias from conflicts of interest. The McMaster University GRADE Centre supported the guideline development process and performed systematic evidence reviews (through November 2021). The panel prioritized clinical questions and outcomes according to their importance for clinicians and patients. The panel used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to assess evidence and make recommendations, which were subject to public comment. This is an update to guidelines published in February 2021 as part of the living phase of these guidelines. RESULTS: The panel made one additional recommendation. The panel issued a conditional recommendation in favor of therapeutic-intensity over prophylactic-intensity anticoagulation in patients with COVID-19-related acute illness who do not have suspected or confirmed VTE. The panel emphasized the need for an individualized assessment of risk of thrombosis and bleeding. The panel also noted that heparin (unfractionated or low molecular weight) may be preferred because of a preponderance of evidence with this class of anticoagulants. CONCLUSION: This conditional recommendation was based on very low certainty in the evidence, underscoring the need for additional, high-quality, randomized controlled trials comparing different intensities of anticoagulation in patients with COVID-19-related acute illness.

A multistakeholder development process to prioritize and translate COVID-19 health recommendations for patients, caregivers and the public. A case study of the COVID-19 recommendation map.

BACKGROUND AND OBJECTIVES: To develop a digital communication tool to improve the implementation of up-to-date COVID-19 recommendations. Specifically, to improve patient, caregiver and public understanding of healthcare recommendations on prevention, diagnoses and treatment. METHODS: Multi-stakeholder engagement design. In conjunction with the COVID-19 Recommendations and Gateway to Contextualization RecMap, we co-developed a stakeholder prioritization, drafting and editing process to enhance guideline communication and understanding. RESULTS: This paper presents the multi-stakeholder development process with three distinct plain language recommendation formats: formal recommendation, good practice statement, and additional guidance. Our case study of COVID-19 plain language recommendations PLRs addresses both public health interventions (e.g., vaccination, face masks) and clinical interventions (e.g., home pulse oximetry). CONCLUSION: This paper presents a novel approach to engaging stakeholders in improving the communication and understanding of published guidelines during the COVID-19 pandemic.

Which actionable statements qualify as good practice statements In Covid-19 guidelines? A systematic appraisal.

OBJECTIVES: To evaluate the development and quality of actionable statements that qualify as good practice statements (GPS) reported in COVID-19 guidelines. DESIGN AND SETTING: Systematic review . We searched MEDLINE, MedSci, China National Knowledge Infrastructure (CNKI), databases of Grading of Recommendations Assessment, Development and Evaluation (GRADE) Guidelines, NICE, WHO and Guidelines International Network (GIN) from March 2020 to September 2021. We included original or adapted recommendations addressing any COVID-19 topic. MAIN OUTCOME MEASURES: We used GRADE Working Group criteria for assessing the appropriateness of issuing a GPS: (1) clear and actionable; (2) rationale necessitating the message for healthcare practice; (3) practicality of systematically searching for evidence; (4) likely net positive consequences from implementing the GPS and (5) clear link to the indirect evidence. We assessed guideline quality using the Appraisal of Guidelines for Research and Evaluation II tool. RESULTS: 253 guidelines from 44 professional societies issued 3726 actionable statements. We classified 2375 (64%) as GPS; of which 27 (1%) were labelled as GPS by guideline developers. 5 (19%) were labelled as GPS by their authors but did not meet GPS criteria. Of the 2375 GPS, 85% were clear and actionable; 59% provided a rationale necessitating the message for healthcare practice, 24% reported the net positive consequences from implementing the GPS. Systematic collection of evidence was deemed impractical for 13% of the GPS, and 39% explained the chain of indirect evidence supporting GPS development. 173/2375 (7.3%) statements explicitly satisfied all five criteria. The guidelines' overall quality was poor regardless of the appropriateness of GPS development and labelling. CONCLUSIONS: Statements that qualify as GPS are common in COVID-19 guidelines but are characterised by unclear designation and development processes, and methodological weaknesses.

COVID-19 transmission during swimming-related activities: a rapid systematic review.

BACKGROUND: There are uncertainties about mitigating strategies for swimming-related activities in the context of the COVID-19 pandemic. There is an opportunity to learn from the experience of previous re-openings to better plan the future one. Our objectives are to systematically review the evidence on (1) the association between engaging in swimming-related activities and COVID-19 transmission; and (2) the effects of strategies for preventing COVID-19 transmission during swimming-related activities. METHODS: We conducted a rapid systematic review. We searched in the L·OVE (Living OVerview of Evidence) platform for COVID-19. The searches covered the period from the inception date of each database until April 19, 2021. We included non-randomized studies for the review on association of COVID-19 transmission and swimming-related activities. We included guidance documents reporting on the strategies for prevention of COVID-19 transmission during swimming-related activities. We also included studies on the efficacy and safety of the strategies. Teams of two reviewers independently assessed article eligibility. For the guidance documents, a single reviewer assessed the eligibility and a second reviewer verified the judgement. Teams of two reviewers extracted data independently. We summarized the findings of included studies narratively. We synthesized information from guidance documents according to the identified topics and subtopics, and presented them in tabular and narrative formats. RESULTS: We identified three studies providing very low certainty evidence for the association between engaging in swimming-related activities and COVID-19 transmission. The analysis of 50 eligible guidance documents identified 11 topics: ensuring social distancing, ensuring personal hygiene, using personal protective equipment, eating and drinking, maintaining the pool, managing frequently touched surfaces, ventilation of indoor spaces, screening and management of sickness, delivering first aid, raising awareness, and vaccination. One study assessing the efficacy of strategies to prevent COVID-19 transmission did not find an association between compliance with precautionary restrictions and COVID-19 transmission. CONCLUSIONS: There are major gaps in the research evidence of relevance to swimming-related activities in the context of the COVID-19 pandemic. However, the synthesis of the identified strategies from guidance documents can inform public health management strategies for swimming-related activities, particularly in future re-opening plans.

A taxonomy and framework for identifying and developing actionable statements in guidelines suggests avoiding informal recommendations.

OBJECTIVE: To propose a taxonomy and framework that identifies and presents actionable statements in guidelines. STUDY DESIGN AND SETTING: We took an iterative approach reviewing case studies of guidelines produced by the World Health Organization and the American Society of Hematology to develop an initial conceptual framework. We then tested it using randomly selected recommendations from published guidelines addressing COVID-19 from different organizations, evaluated its results, and refined it before retesting. The urgency and availability of evidence for development of these recommendations varied. We consulted with experts in research methodology and guideline developers to improve the final framework. RESULTS: The resulting taxonomy and framework distinguishes five types of actional statements: formal recommendations; research recommendations; good practice statements; implementation considerations, tools and tips; and informal recommendations. These statements should respond to a priori established criteria and require a clear structure and recognizable presentation in a guideline. Most importantly, this framework identifies informal recommendations that differ from formal recommendations by how they consider evidence and in their development process. CONCLUSION: The identification, standardization and explicit labelling of actionable statements according to the framework may support guideline developers to create actionable statements with clear intent, avoid informal recommendations and improve their understanding and implementation by users.

American Society of Hematology living guidelines on the use of anticoagulation for thromboprophylaxis in patients with COVID-19: May 2021 update on the use of intermediate-intensity anticoagulation in critically ill patients.

BACKGROUND: COVID-19-related critical illness is associated with an increased risk of venous thromboembolism (VTE). OBJECTIVE: These evidence-based guidelines of the American Society of Hematology (ASH) are intended to support patients, clinicians, and other health care professionals in making decisions about the use of anticoagulation for thromboprophylaxis in patients with COVID-19-related critical illness who do not have confirmed or suspected VTE. METHODS: ASH formed a multidisciplinary guideline panel that included 3 patient representatives and applied strategies to minimize potential bias from conflicts of interest. The McMaster University Grading of Recommendations Assessment, Development and Evaluation (GRADE) Centre supported the guideline development process by performing systematic evidence reviews (up to 5 March 2021). The panel prioritized clinical questions and outcomes according to their importance for clinicians and patients. The panel used the GRADE approach to assess evidence and make recommendations, which were subject to public comment. This is an update on guidelines published in February 2021. RESULTS: The panel agreed on 1 additional recommendation. The panel issued a conditional recommendation in favor of prophylactic-intensity over intermediate-intensity anticoagulation in patients with COVID-19-related critical illness who do not have confirmed or suspected VTE. CONCLUSIONS: This recommendation was based on low certainty in the evidence, which underscores the need for additional high-quality, randomized, controlled trials comparing different intensities of anticoagulation in critically ill patients. Other key research priorities include better evidence regarding predictors of thrombosis and bleeding risk in critically ill patients with COVID-19 and the impact of nonanticoagulant therapies (eg, antiviral agents, corticosteroids) on thrombotic risk.

Canadian Rheumatology Association Recommendation for the Use of COVID-19 Vaccination for Patients With Autoimmune Rheumatic Diseases.

OBJECTIVE: To develop guidance on the use of coronavirus disease 2019 (COVID-19) vaccines in patients with autoimmune rheumatic diseases (ARD). METHODS: The Canadian Rheumatology Association (CRA) formed a multidisciplinary panel including rheumatologists, researchers, methodologists, vaccine experts, and patients. The panel used the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach. Outcomes were prioritized according to their importance for patients and clinicians. Evidence from the COVID-19 clinical trials was summarized. Indirect evidence for non-COVID-19 vaccines in ARD was also considered. The GRADE evidence-to-decision (EtD) framework was used to develop a recommendation for the use of the 4 COVID-19 vaccines approved in Canada as of March 25, 2021 (BNT162b2, mRNA-1273, ChAdOx1, and Ad26.COV2.S), over 4 virtual panel meetings. RESULTS: The CRA guideline panel suggests using COVID-19 vaccination in persons with ARD. The panel unanimously agreed that for the majority of patients, the potential health benefits of vaccination outweigh the potential harms in people with ARDs. The recommendation was graded as conditional because of low or very low certainty of the evidence on the effects in the population of interest, primarily due to indirectness and imprecise effect estimates. The panel felt strongly that persons with autoimmune rheumatic diseases who meet local eligibility should not be required to take additional steps compared to people without ARDs to obtain their vaccination. Guidance on medications, implementation, monitoring of vaccine uptake, and research priorities are also provided. CONCLUSION: This recommendation will be updated over time as new evidence emerges, with the latest recommendation, evidence summaries, and EtD available on the CRA website.

Coronavirus Disease 2019 and Antimicrobial Resistance: Parallel and Interacting Health Emergencies.

The coronavirus disease 2019 (COVID-19) pandemic and antimicrobial resistance (AMR) are parallel and interacting health emergencies that provide the opportunity for mutual learning. As their measures and consequences are comparable, the COVID-19 pandemic helps to illustrate the potential long-term impact of AMR, which is less acute but not less crucial. They may also impact each other as there is a push to use existing antimicrobials to treat critically ill COVID-19 patients in the absence of specific treatments. Attempts to manage the spread of COVID-19 may also lead to a slowdown in AMR. Understanding how COVID-19 affects AMR trends and what we can expect if these trends remain the same or worsen will help us to plan the next steps for tackling AMR. Researchers should start collecting data to measure the impact of current COVID-19 policies and programs on AMR.

Getting trustworthy guidelines into the hands of decision-makers and supporting their consideration of contextual factors for implementation globally: recommendation mapping of COVID-19 guidelines.

Published research on COVID-19 is increasing rapidly and integrated in guidelines. The trustworthiness of guidelines can vary depending on the methods used to assemble and evaluate the evidence, the completeness and transparency of reporting on the process undertaken and how conflicts of interest are addressed. With a global consortium of partners and collaborators, we have created a catalogue of COVID-19 recommendations as our direct response to the increased need for structured access to high quality guidance in the field. The COVID19 map of recommendations and gateway to contextualization (https://covid19.recmap.org) is a living project: emerging guideline literature is added on an ongoing basis, allowing granular access to individual recommendations. Building on prior work on mapping recommendations for the World Health Organization tuberculosis guidelines, a novel feature of this map is the self-directed contextualization of the recommendations using the GRADE-Adolopment approach to adopt, adapt or synthesize de novo recommendations for context specific questions. Through our map, stakeholders access the evidence underpinning a recommendation, select what needs to be contextualized and go through the steps of development of adapted recommendations. This one-stop shop portal of evidence-informed recommendations, built with intuitive functionalities, easy to navigate and with a support team ready to guide users across the maps, represents a long-needed tool for decision-makers, guideline developers and the public at large.

The Conundrum of Giglio Island: Unraveling the dynamics of an apparent resistance to COVID-19 - A descriptive study.

OBJECTIVES: Despite an extensive risk of exposure to COVID-19, the residents of Giglio Island, Italy, did not develop any symptom of SARS-CoV-2. The present study aims to characterize the nature of exposure and to describe the local population dynamics underlying its apparent resistance to COVID-19. METHODS: Descriptive study of an islander partially-segregated population cohort based on a seroprevalence screening conducted from Aprile 29 to May 3, 2020 and including SARS-CoV-2 seroprevalence and viral prevalence in samples of saliva assessed through RT-qPCR. Serologic testing was performed using a COVID-19 IgG/IgM rapid test while molecular analyses were carried out by Allplex 2019-nCoV Assay (Seegene). RESULTS: A total of 634 residents out of 748 (84.8%) present at the time, and 89 non-residents underwent serological testing. 364 males and 359 females with a median age of 58.5 years. The serological screening identified one positive, asymptomatic subject. The Nucleic Acid Amplification Tests (NAAT) did not yield any positive result. CONCLUSION: Despite extensive exposure to SARS-CoV-2, possibly only one new asymptomatic infection occurred in this population, as documented by IgM positivity not confirmed by RT-qPCR. This may be due to unknown protective factors or chance. On the basis of this baseline study, using its population as a reference model, further investigations will be conducted to test the advanced hypotheses, focusing on the evaluation of a possible cross-reactivity to SARS-CoV-2 from exposure to endemic viruses.