Measles Virus IgG Avidity Assay for Use in Identification of Measles Vaccine Failures in Tianjin, China.

To identify measles vaccine failures in Tianjin, China using a measles virus IgG avidity assay. The China Information System for Disease Control and Prevention (CISDCP) was used to collect information about measles cases and blood specimens in Tianjin from 2013 to 2015. Measles-specific IgM and IgG antibodies were detected using Enzyme-Linked Immunosorbent Assay (ELISA). Avidity testing for measles IgG was performed using a commercial enzyme immunoassay (EIA). A total of 284 confirmed measles cases were identified. Of this total, 262 (92.25%) were in patients aged ≥ 20 years. High avidity was exhibited in 172 (60.56%) cases, while 80 (28.17%) cases demonstrated low avidity. High avidity was detected in only 21.43% of cases in patients aged < 1 year. The proportion of high avidity increased with age, and was significantly higher in patients aged 30–39 years at 70.07% (χ ² = 17.27, P = 0.002). Of the 52 measles cases in patients with a history of vaccinations, 41 (78.85%) cases showed high avidity, indicating secondary vaccine failures (SVF). In these vaccinations, there was no significant difference (P > 0.05) in clinical severity between high avidity and low avidity cases. However, regardless of vaccination status, clinical severity was significantly lower in high avidity cases (P < 0.001) than in low avidity cases. The percentages of positive measles IgM results in high avidity and low avidity cases were 66.28% and 91.25%, respectively. Geometric Mean Concentration (GMC) was significantly lower in high avidity cases at 33.73 U/mL, compared to 166.07 U/mL in low avidity cases. Low clinical severity and inconclusive IgM antibody results are more likely in high avidity measles cases. Measles cases were more common in adults. Therefore, a further dose of vaccines should be recommended for 30–39 years in Tianjin. [ABSTRACT FROM AUTHOR]