The seroprevalence of SARS-CoV-2 antibodies among health care workers before the era of vaccination: a systematic review and meta-analysis.

BACKGROUND: The prevalence of SARS-CoV-2 infection among health care workers (HCWs) provides information about the spread of COVID-19 within health care facilities, and the risk groups. OBJECTIVES: We aimed to describe the rate of SARS-CoV-2 seroprevalence and its determinants among HCWs. DATA SOURCES: We used Web of Science, PubMed, Scopus, MEDLINE, EBSCOhost and Cochrane Library. STUDY ELIGIBILITY CRITERIA: We included the reports of SARS-CoV-2 seroprevalence with a sample size of minimum 1000 HCWs. METHODS: The study was registered at the International Prospective Register of Systematic Reviews (PROSPERO, no. CRD42021230456). We used PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. The keywords were "COVID-19", "SARS-CoV-2", "Coronavirus", "seroprevalence", "health care workers" and "risk factors". RESULTS: In total 4329 reports were retrieved, duplications were removed; after filtering according to the title and abstract, 25 studies were selected. Risk of bias was assessed in 25 studies; it was low in 13 studies, medium in four studies, and high in eight studies. In meta-analysis using the random effect model, the weighted average of seroprevalence was calculated as 8% (95% CI 6-10%). The pooled seroprevalence rates of the selected variables that have a rate above the average were male HCWs with 9% (95% CI 7-11%); HCWs from ethnic minorities with 13% (95% CI 9-17%); high exposure 9% (95% CI 6-13%); exposure to the virus outside the health care setting 22% (95% CI 14-32%). CONCLUSIONS: Our analysis indicates a SARS-CoV-2 seroprevalence rate of 8% among studies that included >1000 HCWs for the year 2020, before vaccinations started. The most common risk factors associated with higher seroprevalence rate were ethnicity, male gender and having a higher number of household contacts. Working as a frontline HCW was inconsistent in its association with higher seroprevalence.

Health system modelling research: towards a whole-health-system perspective for identifying good value for money investments in health system strengthening.

Global health research has typically focused on single diseases, and most economic evaluation research to date has analysed technical health interventions to identify 'best buys'. New approaches in the conduct of economic evaluations are needed to help policymakers in choosing what may be good value (ie, greater health, distribution of health, or financial risk protection) for money (ie, per budget expenditure) investments for health system strengthening (HSS) that tend to be programmatic. We posit that these economic evaluations of HSS interventions will require developing new analytic models of health systems which recognise the dynamic connections between the different components of the health system, characterise the type and interlinks of the system's delivery platforms; and acknowledge the multiple constraints both within and outside the health sector which limit the system's capacity to efficiently attain its objectives. We describe priority health system modelling research areas to conduct economic evaluation of HSS interventions and ultimately identify good value for money investments in HSS.

Getting from analysis to action: framing obesity research, policy and practice with a solution-oriented complex systems lens.

Public policy aimed at reducing obesity is just one of many avenues that must be pursued to address the still-growing obesity pandemic. The complexity of the problem is illustrated in ecological frameworks and system maps of the determinants. These conceptual maps illustrate the complexity by acknowledging the influence of many different factors such as social norms and values; sectors of influence such as the food and beverage industries, media and transportation; behavioural settings including home and family, school and community; and individual factors such as genetics, psychosocial and other personal elements. But to solve such a complex problem, we need to move from an analysis of the determinants or causes of the problem to a solution orientation; the frameworks used to describe the problem may not be the right ones for building the "best" solutions. Solution-oriented frameworks, like those presented by Hobbs and Seeman, have been based on parameters such as the sector of influence (e.g., public policy) but would benefit from the consideration of complexity and the leverage points for intervention in complex systems, which are a function of parameters such as the structure of relationships and the presence or absence of feedback loops.

Public and health professionals' misconceptions about the dynamics of body weight gain/loss.

Human body energy storage operates as a stock-and-flow system with inflow (food intake) and outflow (energy expenditure). In spite of the ubiquity of stock-and-flow structures, evidence suggests that human beings fail to understand stock accumulation and rates of change, a difficulty called the stock-flow failure. This study examines the influence of health care training and cultural background in overcoming stock-flow failure. A standardized protocol assessed lay people's and health care professionals' ability to apply stock-and-flow reasoning to infer the dynamics of weight gain/loss during the holiday season (621 subjects from seven countries). Our results indicate that both types of subjects exhibited systematic errors indicative of use of erroneous heuristics. Stock-flow failure was found across cultures and was not improved by professional health training. The problem of stock-flow failure as a transcultural global issue with education and policy implications is discussed.

Places to Intervene to Make Complex Food Systems More Healthy, Green, Fair, and Affordable.

A Food Systems and Public Health conference was convened in April 2009 to consider research supporting food systems that are healthy, green, fair, and affordable. We used a complex systems framework to examine the contents of background material provided to conference participants. Application of our intervention-level framework (paradigm, goals, system structure, feedback and delays, structural elements) enabled comparison of the conference themes of healthy, green, fair, and affordable. At the level of system structure suggested actions to achieve these goals are fairly compatible, including broad public discussion and implementation of policies and programs that support sustainable food production and distribution. At the level of paradigm and goals, the challenge of making healthy and green food affordable becomes apparent as some actions may be in conflict. Systems thinking can provide insight into the challenges and opportunities to act to make the food supply more healthy, green, fair, and affordable.