The next (March 17) issue of The Medical Letter will include a brief article on recent outbreaks of mumps in college students and other young adults. Mumps is transmitted by droplet or fomite exposure with an average incubation period of 16-18 days. The illness has a prodrome of headache, malaise, anorexia and fever, followed within several days by unilateral or bilateral salivary gland swelling, particularly of the parotid.   In recent US outbreaks, orchitis (<10% of postpubertal men), oophoritis (<1% of postpubertal women), pancreatitis (<1%), meningitis (<1%), encephalitis (<1%), and transient high-frequency deafness (<1%) have occurred, but no mumps-related deaths have been reported.

The attenuated live-virus mumps vaccine was first approved in the US in 1967 for use in adolescents. In 1977 it was incorporated into the routine vaccination recommendations for young children. A single dose of measles, mumps and rubella (MMR) vaccine is about 80% effective in preventing mumps; two doses increase protection to 90%. Antibodies may not reach protective levels until 2-4 weeks after vaccination.

The recent mumps outbreaks have occurred mainly in fully vaccinated young adults 10 years or so after their last injection of MMR. Some of these cases may be attributed to primary vaccine failure. Others may be due to a combination of waning immunity and the intense exposure to infection that can occur in settings such as college dormitories or military barracks.

The recommendations coming from public health authorities for responding to outbreaks may strike some health care providers as overly aggressive. They include consideration of vaccinating adults born before 1957, even though people in this age range have always been assumed to have natural immunity. No cases have been reported in older adults, and the safety of MMR vaccine has not, to my knowledge, ever been established in this population.

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  1. Faruk Ali says:

    interesting that it mainly affected those that were already vaccinated with MMR. Could it be that mump virus is becoming resistant to the herd immunity of MMR since 1967?

  2. Walter E Donnelly MD says:

    There is a similar outbreak going on now at The Ohio State University: a total of 68 cases have been confirmed at the school and in surrounding Franklin County . Thank you for your timely article. I have urged them to consider a 3rd dose of MMR to help stop this outbreak.

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