Abstract
BackgroundWorld Health Organization (WHO) has recommended individuals with increased risk of contracting influenza A H5N1 infection to be immunized against the virus during the inter-pandemic period. Safety and immunogenicity of H5N1 vaccine among participants primed with homologous or heterologous H5N1 vaccines produced by diverse manufactures have not been reported.MethodsHealthy individuals aged 20 to 60 years old were recruited and stratified into three groups: participants without priming (control group), participants primed with A/Indonesia/05/2005 vaccine, participants primed with A/Vietnam/1194/2004 vaccine and A/Indonesia/05/2005 vaccine. Enrolled participants received two doses of MF59-adjuvanted A/Vietnam/1194/2004 vaccine (study vaccine). Solicited reactions were recorded by vaccine recipients. Blood samples were obtained for hemagglutination inhibition test.ResultsA total of 131 participants were enrolled. No significant adverse events were recorded. Tenderness, fatigue and general muscle ache were the most common solicited reactions which alleviated within one week of immunization. Three weeks after two doses of the study vaccine, 63%, 68% and 88% were in seroprotective status in the control group, A/Indonesia/05/2005 primed group and A/Vietnam/1194/2004 and A/Indonesia/05/2005 primed group, respectively. Participants primed with A/Vietnam/1194/2004 and A/Indonesia/05/2005 showed high immune response after booster with one dose of the study vaccine.ConclusionThe study vaccine did not cause severe adverse events. It elicited mostly mild to moderate reactions among participants. Participants primed with A/Vietnam/1194/2004 and A/Indonesia/05/2005 vaccine showed higher immune response than those without priming or primed with A/Indonesia/05/2005 vaccine. The report suggested those with an increased risk of influenza A H5N1 virus exposure may benefit from receiving influenza A H5N1 priming during the inter-pandemic period if the antigenicity of the pandemic influenza strain is similar to that of the priming strain.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-014-0587-z) contains supplementary material, which is available to authorized users.
Highlights
World Health Organization (WHO) has recommended individuals with increased risk of contracting influenza A H5N1 infection to be immunized against the virus during the inter-pandemic period
Seven participants who were only primed with two doses of A/Vietnam/1194/2004 vaccine in 2008 and six participants who had received only one dose of A/Vietnam/1194/2004 vaccine in 2008 were excluded from analysis
The rates of solicited local reaction were higher in participants with previous A/Vietnam/1194/2004 and A/Indonesia/05/2005 priming than those without priming or with previous A/Indonesia/05/2005 priming
Summary
World Health Organization (WHO) has recommended individuals with increased risk of contracting influenza A H5N1 infection to be immunized against the virus during the inter-pandemic period. Avian influenza A H5N1 virus was first identified to infect human in Hong Kong in 1997, killing 6 of 18 infected persons [1]. Influenza A H5N1 infection was largely confined in Southeast Asia until 2006 when patients in Turkey contracted the virus [2]. As of Dec 20, 2013, influenza A H5N1 virus had caused 648 cases of human infection; among them, 384 (59.3%) died [3]. The significant morbidity and mortality outcomes caused by influenza A H5N1 infection pose a major threat for the global pandemic. Significance of the clade classification is on the susceptibility of antiviral agents and on the antigenicity, which warrant the preparation of different kinds of H5N1 vaccines [4]
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