[1] Univ Liverpool, Div Med Microbiol, Liverpool L69 3GA, Merseyside, England
[2] Royal Liverpool Childrens Natl Hlth Serv Fdn Trus, Liverpool, Merseyside, England
[3] Hlth Protect Agcy NW, Liverpool, Merseyside, England
[4] Sanofi Pasteur MSD, Maidenhead, Berks, England
[5] Nagasaki Univ, Global Ctr Excellence Program, Nagasaki 852, Japan