To evaluate the safety of diphtheria–tetanus–acellular pertussis–inactivated polio–Haemophilus influenzae type B (DTaP-IPV-HIB) immunization in premature infants.

Observational study of 78 very low birth weight premature infants (mean gestational age, 28±2 weeks; mean birth weight, 1045±357 g) given DTaP-IPV-HIB vaccine before hospital discharge. Apnea, bradycardia, oxygen requirements and saturation, feeding practice, and medical interventions were assessed before and after immunization. The results were analyzed by the severity of the clinical condition and the persistence of prematurity-associated symptoms.

Administration of DTaP-IPV-HIB elicited resurgence or increase in cardiorespiratory events in 47% of infants (15% had apnea, 21% had bradycardia, 42% of desaturations). Most vaccine-triggered events resolved spontaneously or after brief stimulation. The relative risk was 5- to 8-fold higher in infants with a severe clinical course or persistence of cardiorespiratory symptoms at the time of immunization. Bag-mask respiratory support was given to 5 of 78 infants, and O₂ requirements increased transiently in 4 of 21 infants with chronic lung disease, none requiring reventilation. Reintroduction of O₂ supplementation, interruption of active oral feeding, or postponing of hospital discharge was not required.

Cardiorespiratory events were frequently increased after DTaP-IPV-HIB immunization, requiring monitoring and appropriate intervention. However, these episodes did not have detrimental impact on the infants' clinical course. Timely immunization is warranted even in the most vulnerable preterm infants.