Two doses of a vaccine for avian influenza A/H7N9 appeared to protect against infection at antigen-sparing doses, according to a study published in The Journal of Infectious Diseases.1

Anuradha Madan and colleagues from GlaxoSmithKline reported research from a phase 1-2, placebo-controlled, multicenter trial, of 389 healthy adults aged 18-64 years who were randomly assigned to one of 6 groups, ranging from lower doses to higher doses of vaccine or placebo.

The researchers assessed immunogenicity by hemagglutination inhibition (HI) antibody assay and microneutralisation antibody assay at baseline, 21 days after each dose, and at 6 months following the first vaccine dose. Immunogenicity was assessed by HI antibody assay alone 12 months following first vaccine dose.


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Seroconversion rates (85.7% to 96.3%) and seroprotection rates (91.1% to 96.4%) were similar in all adjuvanted vaccine groups.

Madan et al wrote that immune response was ”considerably lower” in the non-adjuvanted vaccine group against both vaccine-homologous and vaccine-heterologous viruses, with seroconversion rates hovering around 23%, seroprotection rates of 29%, and geometric mean titers around 17.

“Adjuvantation with AS03 enabled an immune response that satisfied regulatory acceptance criteria at antigen-sparing concentrations of hemagglutinin (HA), a prerequisite for a pandemic influenza vaccine,” the researchers wrote. “A dose as low as 2.8 μg elicited a robust antibody response.”

Reference

1.     Madan A, Segall N, Ferguson M, et al. Immunogenicity and safety of an AS03-adjuvanted H7N9 pandemic influenza vaccine in a randomized trial in healthy adults. J Infect Dis. 2016;doi: 10.1093/infdis/jiw414.