Dayan, P. 2008, https://doi.org/10.1128/JCM.01803-07), and PRN titers were positive (titers of 1 1:32) (10). (A) Box-and-whisker analysis. The gray dashed line indicates the manufacturers ODR threshold. The black dashed line is usually ODR threshold used in the mumps avidity assay. The number of samples is in parentheses. (B) Receiver operating characteristic curve. The diagonal collection is the area under the curve Arbidol (AUC) of 0.5, interpreted as a random imagine. Ninety-five percent confidence intervals are in parentheses and are plotted as dashed lines. Download FIG?S1, EPS file, 2.2 MB. This is a work of the U.S. Government and is not subject to copyright protection in the United States. Foreign copyrights may apply. FIG?S2. Evaluation of the Zeus mumps IgG enzyme immunoassay optical density ratio (ODR) threshold. Prevaccine samples were collected before mumps vaccination from 15- to 23-month-old infants attending immunization clinics due to upper respiratory symptoms (group E) (46). The uncovered group includes samples drawn from healthy individuals previously exposed to mumps computer virus (groups B and C) and from healthy 15-month-old infants after the first dose of mumps vaccine (group A). (A and B) Box-and-whisker analysis. The gray dashed line indicates the manufacturers ODR threshold. The black dashed line is the ODR threshold used in the mumps avidity assay. Open symbols are values larger than the higher quartile plus 1.5 times the interquartile range. The number of samples is in parentheses. Time of collecting is usually indicated in months and years. Samples are unpaired. (C) Receiver operating characteristic curve. The diagonal collection is an area under the curve (AUC) of 0.5, interpreted as a random imagine. Ninety-five percent confidence intervals are in parentheses and are plotted as dashed lines. Download FIG?S2, PDF file, 0.4 MB. This is a work of the U.S. Government and is not subject to copyright protection in the United States. Foreign copyrights may apply. ABSTRACT Waning mumps IgG antibody and incomplete IgG avidity maturation may increase susceptibility to mumps computer virus infection in some vaccinees. To measure mumps IgG avidity, serum specimens serially diluted to the endpoint were incubated on a commercial mumps-specific IgG enzyme immunoassay and treated with the protein denaturant diethylamine (60?mM, pH 10). End titer avidity indices (etAIs [percent ratio of detected diethylamine-resistant IgG at endpoint]) were calculated. Unpaired Arbidol serum specimens (= 108) from 15-month-old children living in a low-incidence setting were collected 1?month and 2?years after the first measles, mumps, and rubella vaccine dose (MMR1) and tested for mumps avidity. Per the receiver operating characteristic curve, the avidity assay is usually accurate (area under the curve, 0.994; 95% confidence interval [CI], 0.956 to 1 1.000), 96.5% sensitive (95% CI, 87.9 to 99.6%), and 92.2% specific (95% CI, 81.1 to 97.8%) at an etAI of 30%. When 9 units of paired serum specimens collected 1 to 60?months post-MMR1 were tested for mumps and measles IgG avidity using comparable methods, the mumps etAI increased from 11% to 40 to 60% in 6?months. From 6 to 60?months, avidity was sustained at a mean etAI of 50% (95% CI, 46 to 54%), significantly lower (= 51), TLR9 unvaccinated adults with distant mumps disease (= 29), and confirmed mumps cases (= 23) were 54, 62, and 57%, respectively. A mumps-specific endpoint avidity assay was developed and validated, and mumps avidity was decided to be generally sustained at etAIs of 40 to 60%, reaching etAIs of 80% in some individuals. IMPORTANCE Numerous outbreaks of mumps have occurred in the United States Arbidol among two-dose measles-mumps-rubella (MMR)-vaccinated populations since 2006. The avidity of mumps-specific IgG antibodies may impact susceptibility to mumps computer virus contamination in some vaccinated individuals. To accurately measure mumps avidity, we developed and validated a mumps-specific IgG avidity assay that determines avidity at the endpoint titer of serially diluted serum specimens, providing results that are impartial of IgG concentration. At low antibody titers, endpoint methods are considered more accurate than methods that determine avidity at a single dilution. We decided that 6?months after the first MMR dose, mumps IgG avidity is high and generally sustained at avidity indices of 40 to 60%, reaching values of 80% in some individuals. Additionally, 4% (4/103) of individuals experienced avidity indices of 30% (low avidity) 2 years after vaccination. Inadequate mumps avidity maturation may be one factor influencing susceptibility to mumps computer virus contamination among previously vaccinated or naturally infected individuals. = 6%), 40 to 70% (= 8%), and 70% (= 18%). Taking into account the assay variability, etAI values ranged from 0 to 100% (Table?1). The avidity threshold was established at an etAI of 30%, above which all samples are classified as high avidity. This threshold was selected by determining the threshold at which the sensitivity and specificity were highest (etAI of 23%), adding to it the of 6% for the low-avidity control, and rounding up Arbidol to 30%..