 Study population The study population consists of all babies included in the INIS trial. The INIS trial was an RCT of intravenous immunoglobulin two infusions of 500 mgkg body weight polyvalent IgG versus placebo in the treatment of suspected or proven neonatal sepsis.INIS Study Collaborative Group 2008 3493 infants were included from 113 hospitals in nine countries.INIS Collaborative Group 2011 There was no difference between the treatment groups in the primary outcome of death or major disability at the age of two years RR 1.00 95CI 0.92-1.08, or in any of the secondary outcomes. Neither was an effect of immunoglobulin demonstrated in any of the pre-specified subgroup analyses. As the intervention under study did not have an impact on any of the outcomes, secondary observational analyses within the dataset are feasible. 