Very low birth weight infants have only few adverse events after timely immunization.

INTRODUCTION: Premature infants should be vaccinated at the appropriate vaccinating age, without correcting for their gestational week and regardless of their weight. Uncertainty with regard to possible severe adverse events exists among physicians.
METHODS: In all, 473 patients with a birth weight under 1500 g were included in a prospective observational study for adverse events that included cardiorespiratory events, local reactions and fever. Three vaccination combinations were used at different time periods.
RESULTS: The median birth weight was 910 (375 to 1495) g. Gestational week at birth was 27.6 (22.6 to 34.3). At the time of vaccination, the gestational week was 37.4 (31.5 to 48.3). The frequency of adverse events for local reactions/fever was 2.8% and for apnea/bradycardia it was 10.8%. Apnea appeared significantly more often in children who were younger at the time of immunization. This is in concordance with the fact that they were also younger at birth. If apnea appeared, the chance of the development of bradycardia had an odds ratio of 6.4 (3.2:13.0). Children with higher-grade hemorrhages and/or with periventricular leukomalacia did not experience more adverse events, except fever.
CONCLUSION: Timely vaccination of premature infants with a birth weight under 1500 g is safe, but the occurrence of cardiorespiratory events is related to earlier gestational week.