Temporal Confounding in the Test-Negative Design

In the test-negative design, routine testing at health-care facilities is leveraged to estimate the effectiveness of an intervention such as a vaccine. The odds of vaccination for individuals who test positive for a target pathogen is compared with the odds of vaccination for individuals who test negative for that pathogen, adjusting for key confounders. The design is rapidly growing in popularity, but many open questions remain about its properties. In this paper, we examine temporal confounding by generalizing derivations to allow for time-varying vaccine status, including out-of-season controls, and open populations. We confirm that calendar time is an important confounder when vaccine status varies during the study. We demonstrate that, where time is not a confounder, including out-of-season controls can improve precision. We generalize these results to open populations. We use our theoretical findings to interpret 3 recent papers utilizing the test-negative design. Through careful examination of the theoretical properties of this study design, we provide key insights that can directly inform the implementation and analysis of future test-negative studies.

Direct replications in the era of open sampling

Data collection in psychology increasingly relies on “open populations” of participants recruited online, which presents both opportunities and challenges for replication. Reduced costs and the possibility to access the same populations allows for more informative replications. However, researchers should ensure the directness of their replications by dealing with the threats of participant nonnaiveté and selection effects.

Direct replications in the era of open sampling

Data collection in psychology increasingly relies on “open populations” of participants recruited online, which presents both opportunities and challenges for replication. Reduced costs and the possibility to access the same populations allows for more informative replications. However, researchers should ensure the directness of their replications by dealing with the threats of participant nonnaiveté and selection effects.

Overcoming the dichotomy: new insights into the genomic diversity of open and isolated European populations

ABSTRACTHuman populations are often dichotomized into “isolated” and “open” using cultural and/or geographical barriers to gene flow as differential criteria. Although widespread, the use of these alternative categories could obscure further heterogeneity due to inter-population differences in effective size, growth rate, and timing or amount of gene flow. We compared intra and interpopulation variation measures combining novel and literature data relative to 87,818 autosomal SNPs in 14 open populations and 10 geographic and/or linguistic European isolates. Patterns of intra-population diversity were found to vary significantly more among isolates, probably due to differential levels of drift and inbreeding. The relatively large effective size estimated for some population isolates challenges the generalized view that they originate from small founding groups. Principal component scores based on measures of intra-population variation of isolated and open populations turned out to be distributed along a sort of continuum, with an area of intersection between the two groups. Patterns of inter-population diversity were even closer, as we were able to detect some differences between population groups only for a few multidimensional scaling dimensions. Therefore, different lines of evidence suggest that dichotomizing human populations into open and isolated fails to capture the actual relations among their genomic features.