Background: The U.K. Department of Health recommends that infants should receive routine immunization against Hemophilus influenzae at 2, 3, and 4 months of age regardless of gestation. Gestation has been shown not to affect adversely the antibody response to immunization. Dexamethasone which is known to cause immune supression is commonly used in the management of chronic lung disease and may affect the immune response in these infants.

Objectives: To study the effect of Dexamethasone used as treatment of chronic lung disease on routine immunization of preterm infants.

Methods: An unselected cohort of 59 infants of less than 32 weeks gestational age or less than 1500 gm birthweight were entered into the study. Sera were obtained pre- and post- immunisation. HIb antibodies were measured using HbO-HA with monoclonal pan IgG conjugates and differences in the geometric mean titres (GMT) between the two groups of babies analysed.

Results: 16 infants received no Dexamethasone and 43 infants received Dexamethasone. GMT antibody titres to HIb rose from 0.16 to 4.63μg IgG/ml in those not on Dexamethasone and from 0.10 to 0.51 μg IgG/ml in those receiving Dexamethasone (Differences in GMT p=0.047).

Post immunization HIb protection rates were 88% for those not receiving Dexamethasone and 44% for those receiving Dexamethasone (p=0.003).

Conclusion: Dexamethasone therapy used in the treatment of chronic lung disease does appear to have a significant effect on the response of preterm infants to immunization against Hemophilus influenzae.