Immunogenicity and Safety of AS03-Adjuvanted H7N9 Influenza Vaccine in Adults (18–64 and ≥65 Years): A Phase 1/2, Randomized, Placebo-Controlled Trial

Abstract

Background

Influenza A/Hong Kong/125/2017 (H7N9) virus poses a pandemic risk owing to its evolving nature. This study evaluated the immunogenicity and safety of an AS03-adjuvanted H7N9 vaccine in adults (18–64 years [younger] and ≥65 years [older]).

Methods

Participants (younger, n = 418; older, n = 420) were randomized to receive one of six adjuvanted vaccines (hemagglutinin [1.9 μg, 3.75 μg, and 7.5 μg] with AS03_A or AS03_B) or placebo. The co-primary objectives were to determine whether the adjuvanted vaccines elicit an immune response against the vaccine-homologous virus 21 days after the second vaccine dose and to evaluate the safety of the vaccines.

Results

H7N9 AS03-adjuvanted vaccines at various doses showed a humoral immune response but failed to meet CBER immunogenicity criteria. However, a trend of increased immune responses was observed with the AS03_A adjuvant versus the AS03_B adjuvant, particularly in older adults. In both age groups, injection site pain and fatigue occurred more frequently with adjuvanted vaccines. No reported serious adverse events were vaccine-related.

Conclusions

This study did not achieve its primary objective at any dose level. The modest immune response to AS03-adjuvanted vaccines, consistent with other studies using similar antigens, highlights the need for continued research for H7N9 pandemic preparedness.

Trial Registration: NCT04789577 [ClinicalTrials.gov]