Seroepidemiology of measles in Beijing, China: a cross-sectional study.

The aim of this study was to assess the seroprevalence of measles and identify the high risk of measles infection in the general population of Beijing. A total of 2144 subjects aged 0-76 years old were selected using a multi-stage stratified sampling method. Socio-demographic characteristics, vaccination history, and disease history of measles were collected by questionnaire. Serum samples were tested for measles-specific IgG by using commercial ELISA kits. The overall seropositivity rate of measles was 79.80% (95% CI 78.1-81.5%) and standardized seropositivity rate was 84.61% (95% CI 84.12-87.10%), with the median concentration of 773.40IU/L. The area of Beijing with the highest seroprevalence was the central area [81.79% (95% CI 80.16-83.42%) and 855.84IU/L]. There were no significant differences in seropositivity rates of different genders (P = 0.074), history of measles infection (P = 0.421) and registered population (P = 0.598). The 1-4 age group had the highest seropositivity rate [94.06%(95% CI 93.06-95.06%)] and children below the age of 1 (0-12 months) had the lowest seropositivity rate [34.42% (95% CI 32.41-36.43%)]. The 30-34 and 35-39 age groups were relatively lower with 72.90% (95% CI 71.02-74.78%) and 74.65% (95% CI 72.81-76.49%) respectively. Seropositivity rates changed along with the incidence rates of measles periodically by years. As shown in the present study, the seroprevalence of measles antibody in Beijing have not yet met the threshold required to achieve measles elimination and therefore the risk of an epidemic of measles will be existing. Appropriate targeted immunization strategies and measures should be considered and carried out.