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Table 2 Proportion of infections caused by lineage-level mismatched influenza B viruses, compared with the vaccine strain, by season (2004/2005–2016/2017) in Italy

From: Co-circulation of the two influenza B lineages during 13 consecutive influenza surveillance seasons in Italy, 2004–2017

SeasonNorthern Hemisphere TIV B lineage (strain)N. of B viruses characterized (%)Prevalent B lineage in Italy (virus variant)N. of lineage-level mismatched viruses in Italy (%)Seasonal match (m)/
Mismatch (M)
2004/2005*Yam (Sha/361/02)94 (37)Vic (Ill/13/05)67 (71)M
2005/2006*Yam (Sha/361/02)43 (54)Vic (Mal/2506/04)36 (84)M
2006/2007Vic (Mal/2506/04)17 (47)Yam (Flo/4/06)13 (76)M
2007/2008*Vic (Mal/2506/04)99 (38)Yam (Ban/3333/07)80 (81)M
2008/2009Yam (Flo/4/06)10 (22)Vic (Bri/60/08 + Mal/2506/04)7 (70)M
2009/2010Vic (Bri/60/08)30 (58)Vic (Bri/60/08)1 (3)m
2010/2011*Vic (Bri/60/08)303 (38)Vic (Bri/60/08)31 (10)m
2011/2012Vic (Bri/60/08)37 (59)Yam (Wis/01/10)24 (65)M
2012/2013*Yam (Wis/01/10)488 (40)Yam (Mas/02/12)21 (4)m
2013/2014Yam (Mas/02/12)19 (56)Yam (Phu/3073/13)2 (11)m
2014/2015Yam (Mas/02/12)327 (54)Yam (Phu/3073/13)6 (2)m
2015/2016*Yam (Phu/3073/13)866 (61)Vic (Bri/60/08)833 (96)M
2016/2017Vic (Bri/60/08)132 (74)Yam (Phu/3073/13)126 (96)M
All seasons 2465 (49) 1247 (50.6) 
  1. Legenda: Yam: Yamagata; Vic: Victoria; Sha/361/02: B/Shanghai/361/2002; Mal/2506/04: B/Malaysia/2506/2004; Ill/13/05: B/Illinois/13/2005; Flo/4/06: B/Florida/4/2006; Bri/60/08: B/Brisbane/60/2008; Wis/01/10: B/Wisconsin/01/2010; Mas/02/12: B/Massachusetts/02/2012; Phu/3073/13: B/Phuket/3073/2013
  2. * Seasons with at least 20% of all influenza cases due to influenza type B viruses; Mismatch (M): > 60% of the characterized B viruses belonging to the lineage not included in the seasonal TIV