RT Journal Article SR Electronic T1 Responses to a fourth dose of Haemophilus influenzae type B conjugate vaccine in early life JF Archives of Disease in Childhood - Fetal and Neonatal Edition JO Arch Dis Child Fetal Neonatal Ed FD BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health SP F269 OP F271 DO 10.1136/adc.2003.030718 VO 89 IS 3 A1 M H Slack A1 D Schapira A1 R J Thwaites A1 M Burrage A1 J Southern A1 D Goldblatt A1 E Miller YR 2004 UL http://fn.bmj.com/content/89/3/F269.abstract AB Objective: To describe the immune response of preterm infants, with a reduced response to primary Haemophilus influenzae type B (Hib) immunisation, to a fourth dose of Hib conjugate vaccine given in early life. Design: Prospective observational study. Setting: Five Wessex Neonatal Units. Patients: Infants born at < 32 weeks and immunised with three doses of combined acellular pertussis-Hib vaccine, with a Hib IgG geometric mean concentration (GMC) < 1.0 μg/ml after these primary immunisations. Interventions: An additional fourth dose of Hib conjugate vaccine given before 1 year of age. Blood taken to assess Hib IgG concentration and avidity after immunisation. Main outcome measures: Hib IgG GMC and avidity index. Results: Ninety six infants (mean gestational age at birth 29.1 weeks) received a fourth dose of Hib at a mean age of 7.8 months. Hib IgG GMC after the primary immunisations was 0.17 μg/ml (95% confidence interval (CI) 0.14 to 0.20) rising to 4.68 μg/ml (95% CI 3.36 to 6.57) after the fourth dose (p < 0.0001). The IgG response to the fourth dose correlated positively with the response after the primary immunisations (p < 0.001). Hib IgG geometric mean avidity index (GMAI) after the primary immunisations was 30.87 (95% CI 20.40 to 46.73). This increased to 124.73 (95% CI 109.93 to 141.51) after the fourth dose (p < 0.0001). Conclusion: Preterm infants with very low IgG responses to Hib after primary immunisations with a combined acellular pertussis-Hib vaccine mount a good response to a fourth dose of Hib. This study suggests that all infants will benefit from a fourth dose of Hib, regardless of the age at which it is given.