Temporal changes in auditory adverse event reporting in the U.S. vaccine adverse event reporting system associated with the COVID-19 vaccine rollout: an interrupted time series analysis with negative control evaluation.

Objectives: To assess whether auditory adverse event (AE) reporting changed after the COVID-19 vaccine rollout, and whether any change reflected a true safety signal or a shift in reporting behavior. Methods: We analyzed U.S. Vaccine Adverse Event Reporting System (VAERS) data from 2018 through 2025 using interrupted time series (ITS) analysis. The COVID-19 vaccine Emergency Use Authorization (EUA), granted in the fourth quarter of 2020, was treated as a time-level ecological intervention. Because VAERS receives reports for all vaccines, we included every report regardless of vaccine type. We then modeled quarterly auditory AE reporting rates before and after the EUA. Sensitivity analyses stratified results by age, fit quasi-Poisson regression models, used dermatologic events as a reporting-propensity sentinel serving much like a negative control, and compared auditory AE proportions across vaccine types after the EUA (COVID-19 versus influenza versus other). Results: Of 1,347,820 reports, 27,750 involved auditory AEs. Reporting rates rose immediately after the EUA ( Conclusion: Auditory AE reporting increased after the COVID-19 vaccine EUA. The increase was concentrated in adults and showed up across both rate-based and count-based models, although its magnitude remained imprecisely estimated. It was also specific to COVID-19 vaccine reports. Given the inherent limits of passive surveillance and the non-classical nature of the dermatologic reporting-propensity sentinel, these findings argue for targeted investigation in studies with individual-level data, rather than being read as definitive evidence against reporting bias.