Premature infants are at a high risk for pneumonia. The PCV-7 vaccine effectively prevents the invasive disease from Streptococcus pneumoniae in full-term infants, but was not thoroughly studied in premature infants. This study evaluated the effectiveness and safety of the vaccine given in routine practice to very low birth weight infants, looking at blood antibody levels 4-6 weeks after the final vaccine dose, and adverse events, survival, infections, and neurodevelopmental outcomes at 18-22 months corrected age.