Background: Pandemic influenza vaccine manufacturing capacity and distribution agility is enhanced through the availability of equivalent antigen- sparing vaccines. We evaluated equivalence in terms of immunogenicity between GlaxoSmithKline Vaccines' A/California/7/2009 (H1N1)v-like-AS03 vaccines manufactured in Dresden D-Pan), and Quebec (Q-Pan). Methods: In two studies, 334 adults 18-60 years of age received 2 doses of D-Pan or Q-Pan containing 3.75 mu g haemagglutinin antigen (HA) adjuvanted with AS03(A) administered 21 days apart, and 209 children 3-9 years of age received 1 reduced dose of D-Panor Q-Pan (0.9 mu g HA) or Q-Pan (1.9 mu g HA) with AS03(B). Haemagglutination inhibition (HI) titres were assessed before and 21 days post-vaccination. HI persistence was assessed after 12 months in adults and 6 months in children. Results: Pre-defined criteria for immunological equivalence of Q-Pan versus D-Pan were achieved in both populations. After one vaccine dose, >= 97.6% of adults and children had HI titres >= 1:40, with increases in titre >= 25.7-fold. CHMP and CBER regulatory acceptance criteria for influenza vaccines were exceeded by all groups in both studies at Day 21. In adults, the percentage with HI titres >= 1:40 at Month 12 was 82.9% (Q-Pan) and 84.0% (D-Pan). In children, the percentages at Month 6 were 75.3.3% (Q-Pan0.9), 85.1% (D-Pan0.9) and 79.3% (Q-Pan1.9). Safety profile of the study vaccines was consistent with previously published data. Conclusion: Two studies indicate that A/California/7/2009 ( H1N1)v like HA manufactured at two sites and combined with AS03 are equivalent in terms of immunogenicity in adults and children and highly immunogenic. Different HA doses elicited an adequate immune response through 180 days post-vaccination in children 3-9 years of age.