Objectives: To assess the clinical safety of DTaP-IPV-HIb-HBV hexavalent immunization in very premature infants and to verify if the first administration of vaccine is by itself a reason for close monitoring hospitalized VLBW infants born at less than 31 weeks' gestation.
Patients and methods: Eighty-one preterm newborns less than 31 weeks' gestational age, admitted in the NICU, were eligible to be immunized with hexavalent vaccine under close monitoring, including pre-and post-immunization continuous monitoring of heart rate, oxygen saturation, respiratory rate, resistance index at the anterior cerebral artery and ECG cQT interval.
Results: Of the 81 eligible premature newborns, 36 were graduated from the NICU before the least date for immunization, at 7 weeks of age. The other 45 were vaccinated in the NICU and entered the study. Twenty-three of them were under medical treatment for chronic disease at the time of the immunization while 22 were healthy and stable. Five infants (11%) had apnoea/bradycardia/desaturation, related to vaccine administration and required medical support. All five infants were in the group of newborns with chronic disease (21.7% prevalence of adverse reactions in this group). No significant variation of cQT or RI before and after the immunization was observed either in the whole groups of patients or in the five infants who showed cardio-respiratory events related to vaccination.
Conclusions: Hexavalent DTaP-IPV-HIb-HBV immunization is not associated with cardiac electric activity and cerebral blood flow variations in both stable and unstable very premature infants. However, it can cause apnoea/bradycardia/desaturation in premature babies with chronic disease. Therefore, if the baby is in the NICU for chronic diseases at 2 months post-birth, it should be monitored for apnoea, bradycardia and desaturation in association with vaccination. Hospitalized healthy preterm infants without chronic disease and therapy seem to be less vulnerable to cardio-respiratory adverse reactions. Nevertheless, it is advisable to immunize and monitor them at 8 weeks before discharge instead of possibly delaying immunization for several weeks and not monitor them.