PLoS One
[Accessed 16 October 2011]
http://www.plosone.org/article/browse.action;jsessionid=577FD8B9E1F322DAA533C413369CD6F3.ambra01?field=date

7-Valent Pneumococcal Conjugate Vaccination in England and Wales: Is It Still Beneficial Despite High Levels of Serotype Replacement?
Yoon Hong Choi, Mark Jit, Nigel Gay, Nick Andrews, Pauline A. Waight, Alessia Melegaro, Robert George, Elizabeth Miller
PLoS ONE: Research Article, published 14 Oct 2011 10.1371/journal.pone.0026190