Background: Despite the declining trends in measles cases corresponding to an increase in routine measles immunization coverage, measles outbreaks occur in some isolated areas in Nan province, northern Thailand. The primary reason for these outbreaks is inadequate vaccine coverage. Another reason is primary vaccine failure.
Objectives: To study maternal and cord blood measles antibody, the kenetic change of infant measles antibody from 0-9 months and the response to measles vaccine at the age of 9 and 18 months.
Material and method: A prospective cohort study for measles antibody of 1,010 mothers and infants 0-2 years was done between April 1999 and March 2001 at three hospitals in Nan province. Consecutive blood samples were drawn for measles antibody measurement by ELISA assays at Virus Research Institute, National Institute of Health, Thailand. The demographic data of mothers and infants were recorded at each visit.
Results: Maternal and cord blood measles antibody were high and the authors found a higher level in cord blood than in maternal level. Measles antibody level in infants declined significantly from the age of 4 months (246.4 +/- 364.2 mlU/L) to their lowest level at the age of 9 months (17.7 +/- 197.1 mlU/L).
Conclusion: After the first dose of 9-month measles vaccination, the authors found the seroconversion rate of 82.2 percent. The seroconversion rate was significantly higher to 99.6 percent after the second dose at 18 months old.