A clinical trial to assess the immunogenicity and safety of Inactivated Influenza Vaccine (Whole Virion) IP (Pandemic Influenza (H1N1) 2009 Monovalent Vaccine; VaxiFlu-S (TM) ) in healthy Indian adult population

Abstract

Background : The pandemic of H1N1 2009 influenza has spread world over and low degree of virus transmission has continued in several regions of India. Aims : To assess the immunogenicity and safety of Pandemic Influenza (H1N1) 2009 Monovalent Vaccine in healthy adult Indian population. Settings and Design : Prospective, open label, multicentric, phase 2/3 clinical trial. Materials and Methods : Healthy adult Indian subjects belonging to either 18-59 years or >60 years age groups were enrolled and administered a single 0.5 ml (>15 mcg of hemagglutinin antigen) dose of vaccine in the deltoid muscle. Anti-hemagglutinin antibody titer was assessed at baseline and 21 (+-2) days after vaccination by Hemagglutination Inhibition (HI) test. Safety assessments were done for a period of 42 days. Statistical Analysis Used : Percentages of appropriate population with 95% confidence intervals calculated, log transformation of the data to calculate Geometric Mean Titers (GMTs) and chi-square test and student's t-test applied for significance testing. Results : 182/198 and 53/63 volunteers in age groups of 18-59 years and >60 years, respectively, achieved an HI titer >1 : 40 at Day 21 (91.9% [95% confidence interval: 88.1-95.7%] and 84.1% [75.1-93.2%]; P=0.072). Further, 171/198 and 50/63 volunteers in the respective age groups achieved seroconversion/four-fold increase in titer at Day 21 (86.4% [81.6-91.1%] and 79.4% [69.4-89.4%]; P=0.179). A significant rise of 22.6-fold [18.0-28.4] and 10.5-fold [7.4-15.0] was noted in GMT in the respective age groups (P<0.001 for both groups as compared to baseline). Nine vaccine-related adverse events were reported (3.4% incidence [1.2-5.6%]), which were of low severity only. Conclusions : Pandemic Influenza (H1N1) 2009 Monovalent Vaccine produces excellent immunogenic response with a good tolerability profile in adult Indian population.