Waning of maternal measles antibody in the offsprings

Abstract

Objective: Assess the decline of measles antibody, passively acquired from the mother, in infants from birth to nine months of age, and determine the age at which maternal measles antibody declines markedly, making infants susceptible to measles. Methodology: The study was conducted in the departments of Paediatrics and Obstetrics and Gynaecology, Institute of Postgraduate Medicine and Research, Dhaka, during September 1992-December 1993. Children were followed up in the Paediatrics Outpatient Department up to 9 months. Blood samples from 120 full-term infants were collected at birth, at 3, 6, and 9 months of age. Samples of the mothers1 blood were collected within 7 days of delivery. Neasles antibody levels were detected using the ELISA IgG-antibody kit. Results: Eighty-nine percent of the blood samples of the mothers were positive for measles IgG antibody, and were associated with their weights. In infants, this was positive in 91% at birth, and was associated with birth length. The antibody levels were positive in 64% of the infants at 3 months, 21% at 6 months, and only 17% at nine months. This decline with age was highly significant, and was more marked after three months of age. In males, the decline was more marked between 3 and 6 months of age, while in females, it was more marked between 6 and 9 months. Three infants developed measles before they were aged 9 months. Conclusion: The maximum decline in measles antibody occurred in infants during 3-6 months of age. Maternal measles antibody was extremely low at 9 months of age. The study recommends a vaccine trial infants at 6 months of age with the standard measles vaccine in Bangladesh.