Vaccinating premature infants in a Special Care Baby Unit in the UK: results of a prospective, non-inferiority based, pragmatic case series study

Abstract

Premature infants are at greater risk of infections in part because of impaired functioning of external barriers, innate and adaptive systems. For similar immunological reasons, diminished responses to particular vaccines have also been reported. This study, utilising a prospective, pragmatic case series approach was designed to show non-inferiority of antibody response in premature infants to diphtheria, tetanus, Haemophilus influenzae type b conjugate (Hib), meningococcal C conjugate (MenC) and pneumococcal conjugate (PnC) vaccines between immunization in a routine clinical situation rather than a vaccine trial. A secondary objective was to determine the effect of gestational age on antibody response to these vaccines. The case series comprised 131 infants born at ≤ 32 weeks gestation and managed on the Special Care Baby Unit (SCBU) of a District General Hospital in Stockport, UK. For diphtheria and tetanus, 98.3% and 100% of premature infants respectively developed a minimum protective antibody response; 86.6% were protected against Men C. However, only 67.8% preterm infants achieved anti-polyribosylribitolphosphate (PRP) antibodies >0.15μg against Hib, with only 34.7% having a level ≥1.0μg, and responses to the different pneumococcal serogroups ranged from 67.5% against serotype 6B to 92.5% against serogroup 19F. In comparison to term infants, preterm infants were less likely to achieve protective levels against MenC and Hib: there were no significant differences in the proportions of infants protected against diphtheria and tetanus. Protection was inferior to expected based on published premature infant clinical trial data for Hib and particular pneumococcal serotypes; data for Men C were also lower than expected.