Schaffer Andrea, Brotherton Julia, Booy Robert
National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, The Children's Hospital at Westmead and The University of Sydney, NSW, Australia.
J Paediatr Child Health. 2007 Sep;43(9):579-80. doi: 10.1111/j.1440-1754.2007.01205.x.