title: Which influenza vaccine formulation should be used in Kenya? A comparison of influenza isolates from Kenya to vaccine strains, 2007-2013.
abstract: Every year the World Health Organization (WHO) recommends which influenza virus strains should be included in a northern hemisphere (NH) and a southern hemisphere (SH) influenza vaccine. To determine the best vaccine formulation for Kenya, we compared influenza viruses collected in Kenya from April 2007 to May 2013 to WHO vaccine strains.
  
  
  
  We collected nasopharyngeal and oropharyngeal (NP/OP) specimens from patients with respiratory illness, tested them for influenza, isolated influenza viruses from a proportion of positive specimens, tested the isolates for antigenic relatedness to vaccine strains, and determined the percentage match between circulating viruses and SH or NH influenza vaccine composition and schedule.
  
  
  
  During the six years, 7.336 of the 60,072 (12.2%) NP/OP specimens we collected were positive for influenza: 30,167 specimens were collected during the SH seasons and 3717 (12.3%) were positive for influenza; 2903 (78.1%) influenza A, 902 (24.2%) influenza B, and 88 (2.4%) influenza A and B positive specimens. We collected 30,131 specimens during the NH seasons and 3978 (13.2%) were positive for influenza; 3181 (80.0%) influenza A, 851 (21.4%) influenza B, and 54 (1.4%) influenza A and B positive specimens. Overall, 362/460 (78.7%) isolates from the SH seasons and 316/338 (93.5%) isolates from the NH seasons were matched to the SH and the NH vaccine strains, respectively (p<0.001). Overall, 53.6% and 46.4% SH and NH vaccines, respectively, matched circulating strains in terms of vaccine strains and timing.
  
  
  
  In six years of surveillance in Kenya, influenza circulated at nearly equal levels during the SH and the NH influenza seasons. Circulating viruses were matched to vaccine strains. The vaccine match decreased when both vaccine strains and timing were taken into consideration. Either vaccine formulation could be suitable for use in Kenya but the optimal timing for influenza vaccination needs to be determined.
authors.affiliation: US Centers for Disease Control and Prevention-Kenya, P.O. Box 606-00621, Nairobi, Kenya; Department of Biochemistry, University of Nairobi, P.O. Box 30197-00100, Nairobi, Kenya. Electronic address: waiboci@uonbi.ac.ke.
authors.forename: Lilian W
authors.initials: LW
authors.lastname: Waiboci
authors.affiliation: US Centers for Disease Control and Prevention-Kenya, P.O. Box 606-00621, Nairobi, Kenya; US Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30329-4027, USA.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Mott
authors.affiliation: Kenya Medical Research Institute/Centers for Diseases Control and Prevention, P.O. Box 54840-00200, Nairobi, Kenya.
authors.forename: Gilbert
authors.initials: G
authors.lastname: Kikwai
authors.affiliation: Kenya Medical Research Institute/Centers for Diseases Control and Prevention, P.O. Box 54840-00200, Nairobi, Kenya.
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Arunga
authors.affiliation: US Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30329-4027, USA.
authors.forename: Xiyan
authors.initials: X
authors.lastname: Xu
authors.affiliation: Kenya Medical Research Institute/Centers for Diseases Control and Prevention, P.O. Box 54840-00200, Nairobi, Kenya.
authors.forename: Lilian
authors.initials: L
authors.lastname: Mayieka
authors.affiliation: US Centers for Disease Control and Prevention-Kenya, P.O. Box 606-00621, Nairobi, Kenya.
authors.forename: Gideon O
authors.initials: GO
authors.lastname: Emukule
authors.affiliation: Kenya Ministry of Health, Afya House, P.O. Box 30016-00100, Nairobi, Kenya.
authors.forename: Phillip
authors.initials: P
authors.lastname: Muthoka
authors.affiliation: US Centers for Disease Control and Prevention-Kenya, P.O. Box 606-00621, Nairobi, Kenya; Kenya Medical Research Institute/Centers for Diseases Control and Prevention, P.O. Box 54840-00200, Nairobi, Kenya.
authors.forename: M Kariuki
authors.initials: MK
authors.lastname: Njenga
authors.affiliation: US Centers for Disease Control and Prevention-Kenya, P.O. Box 606-00621, Nairobi, Kenya; US Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30329-4027, USA.
authors.forename: Barry S
authors.initials: BS
authors.lastname: Fields
authors.affiliation: US Centers for Disease Control and Prevention-Kenya, P.O. Box 606-00621, Nairobi, Kenya; US Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30329-4027, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Katz
mesh_terms: D006801:Humans; D017589:Immunization Programs; D009980:Influenza A virus / Q000145:classification / Q000302:isolation & purification*; D009981:Influenza B virus / Q000145:classification / Q000302:isolation & purification*; D007252:Influenza Vaccines / Q000737:chemistry* / Q000627:therapeutic use; D007251:Influenza, Human / Q000517:prevention & control*; D007630:Kenya; D009305:Nasopharynx / Q000821:virology
chemical_list: D007252:Influenza Vaccines
keywords: Influenza seasonality; Influenza strains; Influenza vaccines; Timing influenza vaccination