Influenza is a viral infection that attacks the nose, throat, and lungs. The disease remains to be a public health problem as existing vaccines are not entirely protective. The objective of this study is to investigate the safety, efficacy, and immunogenicity of VXA-A1.1, an oral influenza vaccine.

This placebo-controlled, active-controlled, single-site phase 2 study included a total of 179 healthy individuals (age 18-49 years) with an initial A/California/H1N1 haemagglutination inhibition titer of less than 20. The participants were randomly assigned in a 2:2:1 ratio to receive a single immunization of 10 (11) infectious units of VXA-A1.1 orally, a full human dose of a quadrivalent inactivated influenza vaccine (IIV) via intramuscular injection or placebo. The primary outcomes of the study were safety and influenza-positive illness.

The findings suggested that VXA-A1.1 was well-tolerated in all participants with no clinically serious adverse events. Headache was the most prevalent solicited adverse event after immunization in the three treatment groups. The influenza-positive illness was present in 29% of individuals in the VXA-A1.1 group, 35% in the IIV group, and 48% in the placebo group.

The research concluded that orally administered VXA-A1.1 was well-tolerated and more effective in providing immunity against virus shedding, as compared with intramuscular IIV and placebo.