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Background Few studies have assessed participant safety in human challenge trials (HCTs). Key questions regarding HCTs include how risky such trials have been, how often adverse events (AEs) and serious adverse events (SAEs) occur, and whether risk mitigation measures have been effective. Methods A systematic search of PubMed and PubMed Central for articles reporting on results of HCTs published between 1980 and 2021 was performed and completed by 7 October 2021. Results Of 2838 articles screened, 276 were reviewed in full. A total of 15 046 challenged participants were described in 308 studies that met inclusion criteria; 286 (92.9%) of these studies reported mitigation measures used to minimize risk to the challenge population. Among 187 studies that reported on SAEs, 0.2% of participants experienced at least 1 challenge-related SAE. Among 94 studies that graded AEs by severity, challenge-related AEs graded "severe" were reported by between 5.6% and 15.8% of participants. AE data were provided as a range to account for unclear reporting. Eighty percent of studies published after 2010 were registered in a trials database. Conclusions HCTs are increasingly common and used for an expanding list of diseases. Although AEs occur, severe AEs and SAEs are rare. Reporting has improved over time, though not all papers provide a comprehensive report of relevant health impacts. We found very few severe symptoms or SAEs in studies that reported them, but many HCTs did not report relevant safety data. This study was preregistered on PROSPERO as CRD42021247218. [ABSTRACT FROM AUTHOR]

Background Antibiotic noninferiority randomized controlled trials (RCTs) are used for approval of new antibiotics and making changes to antibiotic prescribing in clinical practice. We conducted a systematic review to assess the methodological and reporting quality of antibiotic noninferiority RCTs. Methods We searched MEDLINE, Embase, the Cochrane Database of Systematic Reviews, and the Food and Drug Administration drug database from inception until November 22, 2019, for noninferiority RCTs comparing different systemic antibiotic therapies. Comparisons between antibiotic types, doses, administration routes, or durations were included. Methodological and reporting quality indicators were based on the Consolidated Standards of Reporting Trials reporting guidelines. Two independent reviewers extracted the data. Results The systematic review included 227 studies. Of these, 135 (59.5%) studies were supported by pharmaceutical industry. Only 83 (36.6%) studies provided a justification for the noninferiority margin. Reporting of both intention-to-treat (ITT) and per-protocol (PP) analyses were done in 165 (72.7%) studies. The conclusion was misleading in 34 (15.0%) studies. The studies funded by pharmaceutical industry were less likely to be stopped early because of logistical reasons (3.0% vs 19.1%; odds ratio [OR] = 0.13; 95% confidence interval [CI],.04–.37) and to show inconclusive results (11.1% vs 42.9%; OR = 0.17; 95% CI,.08–.33). The quality of studies decreased over time with respect to blinding, early stopping, reporting of ITT with PP analysis, and having misleading conclusions. Conclusions There is room for improvement in the methodology and reporting of antibiotic noninferiority trials. Quality can be improved across the entire spectrum from investigators, funding agencies, as well as during the peer-review process. There is room for improvement in the methodology and reporting of antibiotic noninferiority trials including justification of noninferiority margin, reporting of intention-to-treat analysis with per-protocol analysis, and having conclusions that are concordant with study results. Clinical Trials Registration PROSPERO registration number CRD42020165040. [ABSTRACT FROM AUTHOR]