Measles and mumps immunization: benefit versus risk factors

Abstract

Measles and mumps are universal diseases that affect more than 90% of the population of most countries of the world. During the prevaccine era about 98% of young adults had serologic evidence of past measles infection. Although mumps infection was less prevalent, about 90% of persons were infected before they reached their 20th birthday. Before vaccines were available, measles and mumps were inevitable infections of childhood. Therefore, an assessment of the benefits and risks of immunization to prevent these diseases must also consider the consequences of naturally acquired measles and mumps infections.

PIP: Both measles and mumps are universal diseases, affecting more than 90% of the population of most countries of the world. In the US, during the prevaccine era, about 500,000 cases of measles were reported each year. Since licensure of measles vaccine in 1963, about 70% of the population of infants and children have been immunized. This extensive use of vaccine has been associated with a progressive decline in the number of reported cases of measles, measles encephalitis, and subacute sclerosing panencephalitis (SSPE). By 1978, the reduction in incidence of measles will exceed 90%. The rising incidence of measles in older persons represents a risk of the present immunization program, but this risk can be eliminated by a more aggressive immunization program. Mumps, usually regarded as a relatively mild disease, is responsible for considerable morbidity in those children and adults who develop fever and painful parotid swelling during the course of the illness. A live attenuated mumps-virus vaccine was licensed for use in the US in January 1968. Experience with this vaccine, the Jeryl Lynn strain, revealed that it was well-tolerated, immunogenic, and protective. Local or systemic reactions rarely were observed; it did not cause fever, and side-effects were negligible. The vaccine induced an antibody response in about 95% of recipients, and persistence of antibody and protection were observed for the 2-year period before licensure. Since licensure of mumps vaccine in 1968, more than 36 million doses have been distributed. This extensive experience confirmed the safety and efficacy of the vaccine. It also revealed evidence of persistence of immunity. The use of more than 36 million doses of mumps vaccine in the US has been followed by a decrease in the number of reported cases from about 200,000 in the prevaccine era to about 20,000 this past year, a 90% reduction in the incidence of mumps.