Tinnitus risk after COVID-19 XBB.1.5 vaccination: A self-controlled case series study.

BACKGROUND: While prior studies found no clear evidence of an association between COVID-19 vaccination and tinnitus, concerns about a potential link remain. This study assessed the risk of tinnitus following COVID-19 XBB.1.5 vaccination, administered alone or coadministered with influenza vaccine, using the event-dependent self-controlled case series (SCCS) design.

METHODS: We conducted an SCCS study among individuals aged ≥12 years enrolled at Kaiser Permanente Southern California, with tinnitus events occurring between September 1, 2023, and March 31, 2024. The exposures included Pfizer-BioNTech and Moderna COVID-19 XBB.1.5 vaccines, with or without influenza vaccine coadministration. The primary outcome was first-ever tinnitus (no documented history before September 1, 2023), and the secondary outcome was first-in-1-year tinnitus, identified using ICD-10 code H93.1* in inpatient, emergency department, and outpatient settings. Risk intervals were pre-specified as 1-14 days and 1-28 days after vaccination, with person-time outside the risk interval serving as the control interval. Relative incidences (RI) and 95% confidence intervals (CI) were estimated, adjusting for seasonality by including tinnitus events among non-recipients of COVID-19 XBB.1.5 vaccines and by including calendar month in the SCCS models.

RESULTS: With 13,940 first-ever tinnitus events among recipients of COVID-19 XBB.1.5 vaccines, no increased risk was observed within 1-14 or 1-28 days following vaccination in overall analyses. The RI was 0.78 (95% CI: 0.67-0.90) for the 14-day risk interval and 0.87 (95% CI: 0.78-0.96) for the 28-day interval. Subgroup analyses by age and influenza vaccine coadministration status also showed no significant increase in RI. Similarly, no significantly elevated RI was found for first-in-1-year tinnitus in the overall analyses, age-specific analyses, or analyses by coadministration with influenza vaccine.

CONCLUSION: Our findings suggest no increased tinnitus risk following COVID-19 XBB.1.5 vaccination, either administered alone or coadministered with influenza vaccine. These results provide reassuring evidence of the safety of COVID-19 vaccines with respect to tinnitus risk.