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It is common practice in the UK to immunise babies with DTP (diphtheria, pertussis, tetanus), Hib (haemophilus influenza type b), meningitis C, and polio at 8 weeks following delivery, regardless of corrected gestational age. However, such recommendations may be inappropriate for premature babies who may be at increased risk of apnoea and bradycardia.1,2
Twenty seven week gestation twins underwent their first immunisations at 62 days of age (corrected age 36+2 weeks) The following morning (15–16 hours later) both twins went a pale, dusky colour and had a respiratory arrest requiring bag and mask ventilation with severe bradycardia. On examination both infants were tachypnoeic and pyrexial. Intravenous antibiotics were started but stopped 48 hours later when full septic screens, viral cultures, and a nasopharyngeal aspirate returned negative. Cardiac and oxygen saturation monitoring showed several further episodes of desaturations, requiring facial oxygen and gentle stimulation. A full recovery to normal self-ventilation in air followed over four hours. Both babies remained pink, active, and with no respiratory distress despite elevated C reactive protein (twin 1: 27 mg/l; twin 2: 38 mg/l; normal <10 mg/l) and raised platelets in twin 1 (420×109/l; normal 150–400). The reactions were reported to the UK Adverse Drug Reactions reporting scheme.
Four weeks later the second immunisation sets using acellular pertussis were administered while cardiorespiratory and oxygen monitoring was performed. Neither twin had any reaction to the second course of immunisations. Current evidence points to an increase in episodes of apnoea and bradycardia in preterm infants receiving their eight week immunisation,2 and the unit has decided to review its policy on the monitoring of such infants.
The episodes of apnoea and bradycardia in the twins following their immunisations were highly suggestive of a delayed type hypersensitivity reaction to a component of one of the vaccines. Studies have implicated the whole cell pertussis component of DTwP with significantly more reactions and raised C reactive protein after immunisation with DTwP than after separate diphtheria, Hib, and tetanus toxoid vaccines alone.2–4
Current opinion for immunisation of preterm infants suggests cardiorespiratory monitoring for up to 48 hours post-immunisation rather than postponement of immunisation;1,2 however, recommendations for future immunisations in infants who have had an episode of apnoea or bradycardia are unclear. Many suggest immunisation with acellular pertussis, as inpatients with 48 hour monitoring.1 However, the evidence from one Australian study implies that the risk of future reaction is very low.5
Competing interests: none declared