Frequency of respiratory deterioration after immunisation in preterm infants

Aim: To determine the relationship between the initiation of respiratory support and the first routine immunisation of neonates at 2 months of age during primary hospitalisation. Methods: An historical cohort study design was used to study the neonatal factors associated with the initiation of respiratory support within 7 days of immunisation in a cohort of 7629 preterm and term infants admitted to the Neonatal Unit of the Royal Women's Hospital between 2001 and 2008. Results: The 411 infants who received their first immunisations in hospital were both very preterm and of extremely low birth weight (ELBW, below 1000 g). Twenty-two infants experienced post-immunisation apnoea of sufficient severity to warrant the initiation of either intermittent positive pressure ventilation (two cases) or continuous positive airway pressure (20 cases). Infants exhibiting a respiratory deterioration following immunisation had a higher incidence of previous septicaemia (Odds ratio 2.5, 95% confidence interval 1.0, 6.1; P = 0.04) and received CPAP for a longer period prior to vaccination (P = 0.03). Conclusion: Apnoea following immunisation may be an aetiological factor in the requirement of respiratory support in a small number of preterm, ELBW infants particularly those with significant lung disease and those who have previously experienced septicaemia.