We found no signifi cant differences in allele frequencies or genotype prevalence for variants in the TNF and MBL2 genes between fatal infl uenza cases in patients <40 years old and a nationally representative reference sample. However, among the case-patients who died, most of whom died in childhood, variants of MBL2 responsible for low production of MBL were associated with MRSA co-infection. This observation should be viewed cautiously as a hypothesis for further exploration, given the small number of case-patients with MRSA in our study (n = 8). This fi nding is consistent with results from previous studies that found associations between MBL insuffi ciency (defi ned by genotype) and respiratory infection in children (12) (13) (14) , severe and fatal sepsis (9, (15) (16) (17) , and systemic infl ammatory response syndrome in children (18) .