The mumps, measles, and rubella (MMR) vaccine is not just for children, but few studies focus on safety outcomes in older people receiving the immunization.
  
Compiling information on use by adults and adolescents in the Vaccine Safety Datalink (VSD), a study in Open Forum Infectious Diseases, estimates the incidence of medically attended outcomes after MMR. The authors said their results could provide information to future studies estimating vaccine-associated risk.

The study population included adults, as well as adolescents, in the VSD who received at least one MMR vaccine from 2010 through 2016. 

Outcomes, which were prespecified based on previous vaccine safety studies, were categorized as either clinically serious, involving anaphylaxis, encephalitis/myelitis, Guillain-Barré syndrome, meningitis, or seizure; or nonserious, such as allergic reaction, arthropathy, fever, injection-site reaction, lymphadenopathy, nonspecific reaction, parotitis, rash, or syncope.

Marshfield Clinic Research Institute–led researchers identified outcomes by searching for ICD-9 and ICD-10 diagnosis codes in postvaccination exposure windows. 

Overall, more than 146,000 adults and adolescents received 162,992 MMR vaccines during the study period. Mean age at vaccination was 33.7 years, 65% were female, and 53% received at least one other vaccine simultaneously, according to the report. 

Demographic and vaccination characteristics varied across age groups. Adults were less likely to have received another vaccination with the MMR; only in the oldest age group of 45 years or older did the percentage reach more than half, 50.7%. Women were far more likely than men to get the MMR vaccination as adults, ranging from more than 70% from age 18 to 44 years to 61.3% at age 45 years and older.

Overall, researchers report, the incidence of validated serious outcomes was low, ranging from 0 to 6.8 per 100,000 vaccinations. In fact, only one serious outcome, anaphylaxis, was noted to be vaccine-associated in the medical records.
 
Incidence of clinically nonserious outcomes varied from 0.4 to 56.0 per 10,000 vaccinations, according to the study team. Compared with adults, injection-site reactions were more common among adolescents (118.1 per 10,000 vaccinations), who also had a higher frequency of simultaneous vaccination (80%).

“Clinically serious outcomes were rare following MMR vaccination,” the authors concluded. “Rates of clinically non-serious outcomes varied but were similar to or lower than previous reports in children. This descriptive analysis did not evaluate the association between MMR and adverse events. Future analysis with an appropriate comparison group is needed for risk estimation.”

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