Clinical trials underway to test adjuvants for flu vaccines

Seasonal flu vaccine efficacy has hovered around 60 percent, varying by age and health status, but researchers are now working to investigate whether certain adjuvants can boost immune responses and improve overall protection.

The National Institute of Allergy and Infectious Diseases (NIAID) is in the early stages of a clinical trial to determine the safety and efficacy of two adjuvants that could induce stronger immune responses on existing influenza vaccines.

The Phase I study is currently enrolling adults to test the adjuvants at eight clinical sites across the country. With the efficacy of existing influenza vaccines varying from year to year, the goal of the trial is to determine whether adjuvants can boost the immune responses generated by these vaccines to result in better overall protection.

“Adjuvants as immune boosting molecules may have the potential to increase the level, quality and duration of the immune response to a given vaccine, providing broader protection against circulating strains of influenza virus,” according to a spokesperson for the NIAID.

Currently, both of the vaccines being tested are only licensed and approved as non-adjuvanted vaccines, according to NIAIS.

Trial researchers expect to enroll 240 adult volunteers between the ages of 18 and 45, and the trial will run for 18 months. Volunteers enrolled in the trial will receive one dose of either Fluzone Quadrivalent or Flublock Quadrivalent influenza vaccines. The vaccines will either be administered alone or in combination with either the AF03 or the Advax-CpG55.2 adjuvants.

These adjuvants have shown promise in animal studies, according to NIAID. The AF03 adjuvant was developed by Sanofi Pasteur and has been shown to be particularly effective in improving immune responses with avian influenza vaccines, while the Advax-CpG55.2 adjuvant from Australia’s Vaxine Pty Ltd has already been linked to improved human immune responses in influenza vaccines in other studies.

While these adjuvants have already been linked to improved immune responses in certain situations, the clinical trial will assess specific uses and safety.

“The primary goals of this study are to evaluate the safety, reactogenicity and immunogenicity of these vaccines when combined with these novel adjuvants,” according to the NIAID spokesperson. “By combining licensed seasonal vaccines with immune boosting adjuvants, it is envisioned that more cross-protective and durable immune responses will be elicited that may improve patient outcomes by providing more robust protection against influenza virus infection and development of severe disease.”

Patients who receive the vaccines with and without adjuvants will be assessed through clinical visits for at least 57 days, during which time adverse effects and blood samples to track immune responses will be monitored. Patients will then be given a dose of seasonal vaccine without adjuvants 90 days after administration of the first vaccine and observed again.

Final assessments will occur a year after the initial vaccination, according to NIAID. The first phase of the trial is expected to conclude in August 2020.