[1] Univ Manchester, Div Human Dev, Manchester M13 0JH, Lancs, England
[2] Univ London London Sch Hyg & Trop Med, Non Communicable Dis Epidemiol Unit, London WC1E 7HT, England
[3] Univ Manchester, Div Human Dev, Manchester M13 0JH, Lancs, England
[4] Cent Manchester & Manchester Childrens Univ Hosp, Dept Cytol, Manchester M13 9WL, Lancs, England
[5] Inst Canc Res, Canc Res UK Epidemiol & Genet Unit, Sutton SM2 5NG, Surrey, England
[6] Cent Manchester & Manchester Childrens Univ Hosp, Dept Virol, Manchester M13 9WL, Lancs, England
[7] Univ Manchester, Div Human Dev, Manchester M13 0JH, Lancs, England
[8] Univ London London Sch Hyg & Trop Med, Non Communicable Dis Epidemiol Unit, London WC1E 7HT, England
[9] Inst Canc Res, Canc Res UK Epidemiol & Genet Unit, Sutton SM2 5NG, Surrey, England