Evaluation of safety and immunogenicity of HNVAC, an MDCK-based H1N1 pandemic influenza vaccine, in Phase I single centre and Phase II/III multi-centre, double-blind, randomized, placebo-controlled, parallel assignment studies

The clinical evaluation of the MDCK-based H1N1 pandemic influenza vaccine HNVAC in adults aged 18-65 years is reported. In the Phase I randomized, double-blind, placebo-controlled, single-centre study, 160 subjects were parallelly assigned 3:1 to vaccine:placebo groups (n = 60:20) with both the aluminium hydroxide adjuvanted and non-adjuvanted vaccine formulations. A single dose of both the formulations containing 15 μg of haemagglutinin protein showed minimal adverse reactions, the most common of which were pain at injection site (11.67%) and fever (10.00%). Both formulations produced 74-81% seroprotection (SRP: titre of ≥40), 67-70% seroconversion (SRC: four-fold increase in titres between days 0 and 21), and a four-fold increase in geometric mean titres (GMT). Aluminium hydroxide did not have a significant effect either on immunogenicity or on reactogenicity. Nevertheless, based on its recognized positive effects on the stability and immunogenicity of many vaccines, and its marginal benefit in both pre-clinical and Phase I studies of HNVAC, alum adjuvanted HNVAC was further tested in a staggered Phase II/III randomized, double-blind, placebo-controlled, multi-centre study of 200 and 195 subjects, respectively, parallelly assigned 4:1 to adjuvanted vaccine and placebo groups. In these studies, the most common adverse reactions were pain at injection site (6.88% and 5.77% in Stage 1 and Stage 2, respectively) and fever (7.50% and 7.05%, respectively), and a single dose resulted in 87-90% SRP, 85-86% SRC, and a nearly six-fold increase in GMT, meeting or exceeding licensing criteria. It is concluded that HNVAC is safe and immunogenic to adults of 18-65 years.