How many children developed hearing loss due to measles before the introduction of the Measles, Mumps, and Rubella (MMR) vaccine in the United States?

Historical Burden of Measles-Related Deafness in the United States Before MMR

Before the MMR vaccine was introduced in 1963, mumps was a major cause of childhood deafness in the United States, though specific numerical data on total cases of measles-related hearing loss are not well-documented in the available evidence. 1

Understanding the Pre-Vaccine Disease Burden

Measles Disease Prevalence

• Approximately 3.5 million measles cases occurred annually in the United States before 1963, representing essentially an entire birth cohort as virtually all children acquired measles. 2
• During the 1950s, an annual average of greater than 500,000 cases of measles and nearly 500 deaths were reported, though surveys indicated that 95% of the population had been infected with measles by age 15 years. 3

Neurological Complications Leading to Hearing Loss

• Wild-type measles causes encephalitis in approximately 1 per 1,000 infected persons, presenting with fever, altered mental status, seizures, and potential permanent CNS impairment including hearing loss. 2
• With 3.5 million annual cases and a 1:1,000 encephalitis rate, this translates to approximately 3,500 cases of measles encephalitis per year in children before vaccine introduction, many of whom suffered permanent brain damage. 2

Mumps as the Primary Cause of Vaccine-Preventable Deafness

• Mumps, not measles, was identified as a major cause of childhood deafness in the pre-vaccine era, with sudden sensorineural deafness being a recognized complication. 1
• The available evidence does not provide specific numerical estimates for total cases of hearing loss attributable to measles versus mumps before MMR introduction. 1

Impact of MMR Vaccination

Disease Reduction

• The introduction of measles vaccine and its widespread use beginning in 1963 resulted in dramatic declines in reported cases, deaths, and complications including encephalitis. 3
• The reported incidence of measles dropped to less than 1% of prevaccine era levels, with 1981 showing only 1.3 cases per 100,000 population compared to an average of 336.3 cases per 100,000 during 1950-1959. 3

Elimination of Complications

• Measles vaccination has essentially eliminated Subacute Sclerosing Panencephalitis (SSPE) in countries with high vaccination coverage, with the decline in SSPE following the decline in measles by approximately seven years. 2, 3
• The MMR vaccine shows no evidence of association with hearing loss, while preventing the neurological complications of wild-type infection that could lead to deafness. 4

Important Clinical Context

The available historical data does not provide precise numbers for measles-specific hearing loss cases, but the evidence clearly demonstrates that wild-type measles infection caused thousands of cases of encephalitis annually, with survivors often experiencing permanent neurological sequelae including potential hearing impairment. 2 The more significant contributor to vaccine-preventable childhood deafness was mumps rather than measles specifically. 1