Table 2. Number of unique BASTs and measures of diversity among invasive meningococcal disease isolates, United Kingdom, 2010–2016*.

Epidemiologic year	No. unique BASTs	No. isolates	No. BASTs/isolate	Simpson index of diversity
2010−11	229	550	0.416	0.976
2011–12	187	439	0.426	0.977
2012–13	226	491	0.460	0.976
2013–14	181	436	0.415	0.960
2014–15	199	572	0.348	0.924
2015–16	155	585	0.265	0.902
Total	803	3,073	0.261	0.963

*BASTs, Bexsero Antigen Sequence Types.