[1] MRC Biostatistics Unit,
[2] University of Cambridge,undefined
[3] MOX laboratory,undefined
[4] Department of Mathematics,undefined
[5] Politecnico di Milano,undefined
[6] CADS-Center for Analysis,undefined
[7] Decisions and Society,undefined
[8] Human Technopole,undefined
[9] CHRP-National Center for Healthcare Research and Pharmacoepidemiology,undefined
[10] University of Milano-Bicocca,undefined
[11] Department of Medical Statistics,undefined
[12] London School of Hygiene & Tropical Medicine,undefined