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