Seroepidemiology of measles in immune generation in Taiwan: Prevalence of neutralizing antibody and immune response to reimmunization

BackgroundSecondary vaccine failure was the principal mechanic of measles reemergence in countries with high measles vaccine coverage. The information on neutralizing antibody (nAb) prevalence, epidemiological factors of waned immunity and immune response after reimmunization was essential to measles control but largely lacking in Taiwan.MethodsThe nAb and factors of wanned immunity to measles were evaluated in a cohort of 333 subjects aged 11–30 years in 2010. The longitudinal immune response to reimmunization (n = 30) and potential virus exposure (n = 24) were assessed in young healthcare workers (HCWs) during a hospital outbreak. The nAb titer was used to define susceptibility to measles disease (<120 mIU/mL) and infection (120–900 mIU/mL).ResultsIn the 2010 cohort, the susceptibility to measles diseases and infections was respectively identified in 35 (10.5%) and 226 (67.9%) subjects. A generalized linear model identified earlier ages of first immunization in childhood (P = 0.0214) and subjects aged ≥18 years (versus <18 years, P = 0.0425) as significant factors associated with lower nAb titers. Reimmunization of 30 seronegative HCWs resulted in seroconversion for all, with nAb titers significantly rising on day 5, peaking on day 15 and declining in month 4 post-immunization. Similar measles-specific IgG levels were observed in 24 seropositive HCWs before and 4 months after measles contact (P = 0.2352).ConclusionA lack of protective immunity to measles diseases might be identified in 10% of the Taiwanese population aged 11–30 years and associated with a trend toward earlier ages of the first measles vaccination. The wanned immunity can be boosted promptly by reimmunization but with uncertain durability.