Background The World Health Organization recently described sudden sensorineural hearing loss (SSNHL) as a possible adverse effect of COVID-19 vaccines. Recent discordant pharmacoepidemiologic studies invite robust clinical investigations of SSNHL after COVID-19 messenger RNA (mRNA) vaccines. This postmarketing surveillance study, overseen by French public health authorities, is the first to clinically document postvaccination SSNHL and examine the role of potential risk factors. Objective This nationwide study aimed to assess the relationship between SSNHL and exposure to mRNA COVID-19 vaccines and estimate the reporting rate (Rr) of SSNHL after mRNA vaccination per 1 million doses (primary outcome). Methods We performed a retrospective review of all suspected cases of SSNHL after mRNA COVID-19 vaccination spontaneously reported in France between January 2021 and February 2022 based on a comprehensive medical evaluation, including the evaluation of patient medical history, side and range of hearing loss, and hearing recovery outcomes after a minimum period of 3 months. The quantification of hearing loss and assessment of hearing recovery outcomes were performed according to a grading system modified from the Siegel criteria. A cutoff of 21 days was used for the delay onset of SSNHL. The primary outcome was estimated using the total number of doses of each vaccine administered during the study period in France as the denominator. Results From 400 extracted cases for tozinameran and elasomeran, 345 (86.3%) spontaneous reports were selected. After reviewing complementary data, 49.6% (171/345) of documented cases of SSNHL were identified. Of these, 83% (142/171) of SSNHL cases occurred after tozinameran vaccination: Rr=1.45/1,000,000 injections; no difference for the rank of injections; complete recovery in 22.5% (32/142) of cases; median delay onset before day 21=4 days (median age 51, IQR 13-83 years); and no effects of sex. A total of 16.9% (29/171) of SSNHL cases occurred after elasomeran vaccination: Rr=1.67/1,000,000 injections; rank effect in favor of the first injection (P=.03); complete recovery in 24% (7/29) of cases; median delay onset before day 21=8 days (median age 47, IQR 33-81 years); and no effects of sex. Autoimmune, cardiovascular, or audiovestibular risk factors were present in approximately 29.8% (51/171) of the cases. SSNHL was more often unilateral than bilateral for both mRNA vaccines (P<.001 for tozinameran; P<.003 for elasomeran). There were 13.5% (23/142) of cases of profound hearing loss, among which 74% (17/23) did not recover a serviceable ear. A positive rechallenge was documented for 8 cases. Conclusions SSNHL after COVID-19 mRNA vaccines are very rare adverse events that do not call into question the benefits of mRNA vaccines but deserve to be known given the potentially disabling impact of sudden deafness. Therefore, it is essential to properly characterize postinjection SSNHL, especially in the case of a positive rechallenge, to provide appropriate individualized recommendations.
BACKGROUND Sudden sensorineural hearing loss (SSNHL) has recently been reported as a possible adverse effect of mRNA COVID-19 vaccination. However, no studies have described the clinical characteristics of post-vaccination SSNHL in terms of severity or duration nor examined the facilitating role of potential risk factors through a large and intensive post-marketing surveillance. OBJECTIVE The aim of this study is to evaluate the relationship between SSNHL and exposure to mRNA COVID-19 vaccines and estimate the reporting rates (RR) of mRNA-vaccines induced SSNHL. METHODS A national cross-sectional audiogram-based study was conducted using the French pharmacovigilance surveillance system for COVID-19 vaccines. All suspected cases of SSNHL after mRNA COVID-19 vaccination between January 2021 and February 2022 were examined based on a comprehensive audiological, and medical evaluation, including patient history, unilaterality or bilaterality of hearing loss, degree, and recovery after at least 3 months of follow-up. Using French administrative data, the RR of the two mRNA vaccine-induced SSNHL cases were also calculated according to the number of dose of each vaccine (tozinameran and elazomeran) administered during this period. RESULTS Results A total of 400 cases of SSNHL were reported for the two mRNA vaccines during this period, of which 171 (43%) well-documented cases could be retained: 142 SSNHL cases after Tozinameran vaccination (RR=1.45/1,000,000 injections; no difference between the first, second and booster injections; full recovery=37 cases; median interval between vaccine administration and symptom onset (i.e. delay onset) for delay onsets ≤21 days =4 days; median (range) age=51 (13-83) years; no sex effect), and 29 cases after Elasomeran vaccination (RR=1.67/1,000,000 injections; rank effect in favor of the first injection (p=0.036); full recovery=8 cases; median delay onset for delay onsets ≤21 days =8 days; median (range) age=47 (33-81) years; no sex effect). Autoimmune, cardiovascular, or audiovestibular risk factors were present in 50 (35%) Tozinameran cases and 9 (31%) Elasomeran cases. SSNHL was more often unilateral than bilateral (p<0.001 for Tozinameran) and its degree was mild to moderately severe on 71/118 (60%) audiogram tests. A positive rechallenge was identified in 5 cases for Tozinameran and 3 cases for Elasomeran immunisations. CONCLUSIONS This study identified very rare cases of SSNHL for which the role of mRNA COVID-19 vaccination was supported, considering both diagnosis and onset time criteria. Given the benefits of vaccination and the possible occurrence of profound deafness and positive rechallenge, it is essential to thoroughly characterize any post-injection SSNHL cases, before providing individualized recommendations.
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