Nationwide survey of hearing loss caused by mumps during 2015-2016 in Japan

The vaccination rate for mumps has declined to around 40% because of occasional reports about aseptic meningitis associated with the mumps vaccine that have appeared in recent years. Consequently, outbreaks of mumps have periodically reappeared. Although mumps usually causes unilateral hearing loss, bilateral hearing loss can occur in rare cases, leading to considerable socioeconomic disadvantages and the creation of serious obstacles in daily life. However, the actual situation of hearing loss associated with mumps is not well known. The Oto-Rhino-Laryngological Society of Japan conducted a nationwide survey of 5,565 facilities specializing in otorhinolaryngology to investigate hearing loss caused by mumps between 2015 and 2016. Responses were obtained from 3,906 facilities (response rate: 70%), revealing that at least 359 patients developed hearing loss during this period. Among the 335 patients for whom sufficient data was available, 320 patients had unilateral hearing loss and 15 patients had bilateral hearing loss. In addition, the persistent hearing loss was severe or worse in 290 patients with unilateral loss and 12 patients with bilateral loss, even when the ear with better hearing was tested. The patients ranged in age from 0 years to 78 years, and the peak age range was identified as being from 3 years to 15 years, followed by the child-rearing generation in their 30s. Among the 203 patients who were followed from the time of the initial consultation to the final hearing, a worsening of auditory function over time was confirmed in 52 patients; many of them developed profound hearing loss. In contrast, an improvement in hearing was only noted in 11 patients. Because the benefits of vaccination are difficult to recognize, the Oto-Rhino-Laryngological Society should provide information about the value of vaccination for preventing mumps, work to standardize the periodic vaccination schedule, and request the development of new and safer vaccine strains for this disease.