Table 1.

Comparison of vaccine B lineage and circulating B lineages in the seasons 2000/2001–2011/2012. The last two columns indicate whether there was any antigenic drift within each of the two lineages between the vaccine strain selection and the influenza season. The strains Florida/06 and Massachusetts/12 belong to the same antigenic cluster. The strain s Wisconsin/10 and Phuket/13 belong to the same antigenic cluster.

Season	Vaccine strain	Dominant circulating strain	Secondary strain (if co-circulation)	Interim drift in Yam	Interim drift in Vic
2000/2001	Yam—Beijing/93	Yam—Sichuan/99	None	Some, SI/99 distinct from BE/93	–
2001/2002	Yam—Sichuan/99	Vic—Brisbane/02	Yam—Sichuan/99	None	–
2002/2003	Vic—Hong Kong/01	Vic—Brisbane/02	None	None	Some, BR/02 distinct from HK/01
2003/2004	Vic—Hong Kong/01	Yam—Shanghai/02	None	Some, SH/02 distinct from SI/99	None, very little Vic and BR/02-like
2004/2005	Yam—Shanghai/02	Yam—Shanghai/02	Vic—Brisbane/02	None	None
2005/2006	Yam—Shanghai/02	Vic—Malaysia/04	Yam—Shanghai/02	None	Some, ML/04 distinct from BR/02 and HK/01
2006/2007	Vic—Malaysia/04	Vic—Malaysia/04	Yam—Shanghai/02 & Florida/06	Minor, mainly genetic change, SH/02 and FL/06 antigenically similar	None
2007/2008	Vic—Malaysia/04	Yam—Florida/06 & Bangladesh/07	None	Some, FL/06 and BA/07 different enough to warrant vaccine update	None
2008/2009	Yam—Florida/06	Vic—Brisbane/08	Yam—Florida/06 & Bangladesh/07	None	Some, BR/08 distinct from ML/04
2009/2010	Vic—Brisbane/08	Vic—Brisbane/08	very little Yam	None	None
2010/2011	Vic—Brisbane/08	Vic—Brisbane/08	Yam—Wisconsin/10	None	None
2011/2012	Vic—Brisbane/08	Vic—Brisbane/08	Yam—Florida/06 & Wisconsin/10	To previous Florida/06 like (except China Wisconsin/10 like)	None
2012/2013	Yam—Wisconsin/10	Vic—Brisbane/08	Yam—Florida/06 & Wisconsin/10	None	None
2013/2014	Yam—Massachusetts/12	Yam—Wisconsin/10	Vic—Brisbane/08	To Wisconsin/10 everywhere	None
2014/2015	Yam—Massachusetts/12	Yam—Phuket/13	Vic—Brisbane/08	None	None