Serological testing for immunity to mumps (and measles, rubella and varicella) is not recommended before or after routine administration of the 2-dose childhood schedule of these vaccines.
Alternatively, these people can receive MMR vaccine without serological testing. There is no known increase in adverse events from vaccinating people with pre-existing immunity to one or more of the vaccine antigens. See Adverse events.
Serological tests for immunity to mumps can detect antibody produced by both previous natural infection and vaccination. Sensitivity varies by assay and clinical setting (including time since vaccination).1
When interpreting serological testing results, it may be useful to discuss the results with the laboratory that performed the test, to ensure that decisions are based on all relevant clinical information.