| Summary: | Premature infants represent 7% of all births in the UK and have higher rates of vaccine preventable infections. National recommendations for vaccine schedules focus predominantly on term infants. We aimed to assess the immunogenicity of the UK immunisation schedule in preterm infants randomising infants to 3 different PCV13 primary schedules and using data from the randomized controlled trial and a pooled data metaanalysis of preterm vaccine studies to identify factors affecting vaccine responses. Methods 210 infants «35 weeks gestation) received DTaP-IPV-Hib vaccine at 2, 3 and 4 months of age and meningococcal C conjugate vaccine at 2 and 3 months alongside 3 different PCV13 vaccine schedules (Group1: 2 and 4 months, Group 2: 2, 3 and 4 months, Group 3: 2,4 and 6 months). At 12 months of age participants received MMR, PCV13 and Hib-MenC-TI vaccines. Antibody concentrations and Iymphocyte subpopulations were measured before and one month after primary and booster vaccinations. Results The median birth gestation was 29+6 weeks (range 23+2-34+6). Younger gestation was associated with lower antibody concentrations at baseline but had limited effect on vaccine responses. For PCV13, group 3 had the highest antibody concentrations post-primary and prior to booster vaccination but the lowest antibody concentrations after the booster. There was no consistent effect of chronic lung disease, growth restriction or the receipt of blood products, antenatal or postnatal steroids on vaccine responses. For all antibodies a longer duration of vaccine course or an older age at final immunisation was associated with improved immunogenicity. Increased CD19+was associated with improved PCV13 immunogenicity Conclusion Premature infants can mount satisfactory responses to all routine vaccines but the schedule followed for PCV13 vaccine will significantly influence when optimal protection occurs. Disease epidemiology must be considered when deciding which schedule to follow.
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