Were the WHO-recommended Human Influenza Vaccine Formulations Appropriate for Kenya During the 2010-2011 Season? Inferences from the HA1 Gene Analysis

Abstract

Influenza is an acute respiratory illness that spreads across the world in annual epidemics and occasional pandemics (WHO, 2003). In annual epidemics, the disease infects about 5 - 15% of the human population with an estimated 3-5 million severe disease cases and 250,000 - 500000 deaths (Lin et al, 2004). Influenza A and B viruses are the main causative agents of the disease (Baras et al, 2008). Type A influenza viruses are further classified into subtypes based on antigenic properties of surface glycoproteins, hemagglutinin (HA), and neuraminidase (NA). Only a limited number of subtypes have been associated with infections in humans (Baras et al, 2008). Since 1977, subtypes H1N1 and H3N2 viruses have widely cocirculated in the human population (Wang et al, 2009).