Cause analysis of high incidence of measles in infants at a young age in Ningbo

Objective The study was conducted to uncover the cause that precipitated the high incidence of measles in infants at a young age in Ningbo, providing evidence for the development of measles immunization strategies aiming to reduce the incidence of young infant measles. Methods Analyze was made upon the data of measles epidemic from 2004 through 2007. Maternally derived antibodies were analyzed using serological epidemiological approaches. Results　Significant changes in epidemiological characteristics of measles were observed. Two peaks of incidence were noticed in infants less than one year of age and adults. In particular, those less than eight-month-old and eight-month-old to one-year-old of age had amounted to an increasing proportion in the age distribution. It was found that measles vaccination was not given in a timely manner to 146 out of 174 investigated infants (83.9%) who were aged 8 to 12 months. A declining positive rate of measles antibodies was noticed among infants aged 0 to 8 months in proportion to their ages, the rates for 6-month-olds and 8- month-olds being merely 4.1% and 0.8%, and GMRT 4.2 and 1.6, respectively. Conclusion Maternally derived measles antibodies reduce with the growth of infants. Therefore, 6-month-old and 8-month-old infants have too low antibody levels to protect them from measles. Inappropriate and inadequate vaccination is one of the causes that led to the high incidence of measles in infants at a young age in Ningbo.