Antimeasles antibodies in preterm infants during early infancy in Turkey

Aim: To measure maternally derived measles antibodies in sera of premature infants at birth and seropositivity rates in early infancy in a rural area of central Turkey. Methods: 65 premature and 24 full-term infants born in Erciyes University Hospital and their mothers were recruited to a longitudinal, prospective study. The infants were divided into three groups by gestational age: group A, < 33 weeks; group B, 33-37 weeks; group C, > 37 weeks. For specific analyses, the groups were subdivided into groups A1, B1 and C1 (infants of naturally immunised mothers) and A2, B2 and C2 (infants of vaccinated mothers). Blood samples were obtained from mothers and infants after delivery. The infants were re-evaluated at 2, 4 and 6 months of age. Results: Of 25 mothers, 20.3% were seronegative for measles antibodies. Twenty of the mothers had not been vaccinated. The percentages of seronegative infants at birth were 24.2% (n = 8), 12.5% (n = 4) and 0% (n = 0) in groups A, B and C, respectively. No infants were seronegative at birth in A1, B1 or C1. Mean levels of antimeasles antibodies in all naturally immunised mothers were significantly higher than in vaccinated mothers. Antibody levels in all infants decreased rapidly with increasing age. Gestational age at birth [beta = 0.179, t = 3.359, 95% confidence interval (CI) 0.0001-0.0001, p < 0.05], birthweight (beta = 0.637, t = 9.691, 95% Cl 0.057-0.086, p < 0.05) and maternal naturally immunised status (beta = 0.168, t = 2.8253, 95% CI 0.002-0.014, p < 0.05) were significantly associated with antibody levels after birth. In all groups of naturally immunised mothers, the percentages of seronegative infants were significantly lower than in vaccinated mothers at birth and at 2, 4 and 6 months of age. Conclusion: The current recommendation to immunise all infants at 9 months of age might require revision for premature infants, especially those whose mothers have vaccination-induced immunity.