This study is aimed at detecting the rate of untimely immunization in a large cohort
of extremely low gestational age neonates (ELGANs) of the German Neonatal Network (GNN)
and at addressing risk factors for delayed vaccination and associated long-term consequences. We
performed an observational study of the GNN between 1st January 2010 and 31st December 2019.
The immunization status for the hexavalent and pneumococcal immunization was evaluated in
n = 8401 preterm infants <29 weeks of gestation. Univariate analysis and logistic/linear regression
models were used to identify risk factors for vaccination delay and outcomes at a 5-year follow-up.
In our cohort n = 824 (9.8%) ELGANs did not receive a timely first immunization with the hexavalent
and pneumococcal vaccine. Risk factors for delayed vaccination were SGA status (18.1% vs. 13.5%;
OR 1.3; 95% CI: 1.1–1.7), impaired growth and surrogates for complicated clinical courses (i.e.,
need for inotropes, necrotizing enterocolitis). At 5 years of age, timely immunized children had
a lower risk of bronchitis (episodes within last year: 27.3% vs. 37.7%; OR 0.60, 95% CI: 0.42–0.86)
but spirometry measures were unaffected. In conclusion, a significant proportion of ELGANs
are untimely immunized, specifically those with increased vulnerability, even though they might
particularly benefit from the immune-promoting effects of a timely vaccination