Passive immunity of premature infants against measles during early infancy.

The aim of this study was to evaluate the presence of transferred measles antibodies and seronegativity rates during early infancy in premature newborns whose mothers had infection-induced immunity. The premature group was composed of 22 and 35 newborns of gestational ages < 32 wk and > 32 wk, respectively, and the control group consisted of 28 term newborns. Enzyme-linked immunosorbent assay (ELISA) was used for the qualitative detection of IgG antibodies to measles virus. Mean cord blood relative values were significantly lower in both premature groups, < or = 32 wk (p < 0.0001) and > 32 wk (p < 0.001), when compared with term infants. No seronegative infant was found in the premature group at 2 mo of age. At 4 mo, the seronegativity rate was 27% for premature infants < or = 32 wk and 35% for those > 32 wk. At 6 mo, seronegativity increased to 86% and 74% for premature infants born at gestational ages < or = 32 wk and > 32 wk, respectively. Forty-six percent of the term infants became seronegative at that age. The differences between term infants and those in the two premature groups were statistically significant (p < 0.05 and p < 0.005). Premature infants, regardless of their prematurity degree, were thought to be more susceptible to measles infection than term ones at the age of 6 mo. Policies for their protection from measles infection are still to be investigated.