1. Department of Infection, Immunity and Cardiovascular Disease (R.C.O., W.A.E.P., M.R.T., H.M.J., W.S., H.C.M., J.I., J.P.G., R.F.S.), University of Sheffield, United Kingdom.
2. Sheffield Teaching Hospitals National Health Service Foundation Trust, United Kingdom (R.C.O., W.A.E.P., M.R.T., W.S., K.P.M., H.C.M., J.D.R., E.D.G., N.M.W., I.R.H., J.I., D.B., J.P.G., R.F.S).
3. University of Birmingham, United Kingdom (M.R.T.).
4. Statistical Services Unit, (K.B.), University of Sheffield, United Kingdom.