Table 3.
Distribution of Influenza B/Victoria and B/Yamagata Lineage Types Circulating in Kenya Compared With Influenza Vaccine Hemisphere Composition by Year From 11 Surveillance Sites in Kenya, 2012–2016
| Season | All Influenza Positive | Influenza B Positive | Influenza B Type | B/Victoria | B/Yamagata | TIV Influenza B Vaccine Component | Influenza B Cases not Covered by Available Vaccinec |
|---|---|---|---|---|---|---|---|
| No. (%) | No. | No. (%) | No. (%) | % | |||
| Apr 2012–Sep 2012 (SH) | 210 | 96 (45.7) | 59 | 53 (89.8) | 6 (10.2)c | B/Brisbane/60/2008 (B/Victoria) | 10 |
| Oct 2012–Mar 2013 (NH) | 329 | 99 (30.1) | 88 | 63 (71.6) | 25 (28.4) | B/Wisconsin/1/2010 (B/Yamagata)a | 72 |
| Apr 2013–Sep 2013 (SH) | 225 | 95 (42.2) | 67 | 3 (4.5) | 64 (95.5) | B/Wisconsin/1/2010 (B/Yamagata) | 4 |
| Oct 2013–Mar 2014 (NH) | 220 | 52 (23.6) | 26 | 0 (0.0) | 26 (100.0) | B/Massachusetts/2/2012 (B/Yamagata) | 0 |
| Apr 2014–Sep 2014 (SH) | 395 | 18 (4.6) | 7 | 0 (0.0) | 7 (100.0) | B/Massachusetts/2/2012 (B/Yamagata) | 0 |
| Oct 2014–Mar 2015 (NH) | 184 | 75 (40.8) | 57 | 4 (7.0) | 53 (93.0) | B/Massachusetts/2/2012 (B/Yamagata) | 7 |
| Apr 2015–Sep 2015 (SH) | 413 | 93 (22.5) | 66 | 4 (6.1) | 63 (95.5) | B/Phuket/3073/2013 (B/Yamagata)b | 6 |
| Oct 2015–Mar 2016 (NH) | 210 | 179 (85.2) | 149 | 141 (94.6) | 9 (6.0) | B/Phuket/3073/2013 (B/Yamagata)a | 95 |
| Apr 2016–Sep 2016 (SH) | 200 | 82 (41.0) | 39 | 34 (87.2) | 5 (12.8) | B/Brisbane/60/2008 (B/Victoria) | 13 |
Abbreviations: NH, time when the Northern Hemisphere vaccine is available; SH, time when the Southern Hemisphere vaccine is available; TIV, trivalent influenza vaccine.
aSeasons with a mismatch of the influenza B component of the TIV vaccine.
bHad 1 patient with a co-infection of B/Victoria and B/Yamagata.
cCalculated as the crude percentage of influenza B cases that would not be potentially protected by the available TIV vaccine assuming no cross-protection.