US scientists conduct clinical trial of influenza vaccine with imiquimod

A Phase 1 clinical trial examining whether a topical cream can enhance the immune response conferred by a “pre-pandemic” influenza vaccine is underway at Baylor College of Medicine in Houston (USA).

Investigators are evaluating whether imiquimod cream, which is commonly used to treat genital warts and certain skin cancers, can boost the body’s immune response to an H5N1 influenza vaccine. The trial is enrolling 50 healthy adults ages 18-50 years. Baylor is one of the Vaccine and Treatment Evaluation Units (VTEUs) — a network of clinical research sites that can rapidly enroll large volunteer cohorts to evaluate experimental vaccines against infectious diseases. The VTEUs are funded and managed by the U.S. National Institute of Allergy and Infectious Diseases (NIAID), part of the U.S. National Institutes of Health.

H5N1 is an avian influenza virus that causes severe respiratory illness in birds. In rare circumstances, humans have contracted H5N1 influenza through direct or indirect contact with infected birds, such as poultry. Participants in the VTEU trial will receive an H5N1 vaccine (manufactured by Sanofi Pasteur, based in Swiftwater, Pennsylvania) that was designed for use in a potential pandemic. The vaccine is made from an inactivated, or “killed,” influenza virus. After the vaccine was approved by the Food and Drug Administration (FDA) in 2007, it was added to the National Pre-pandemic Influenza Vaccine Stockpile.

Imiquimod cream activates the innate immune system — the body’s immediate defense against invading pathogens. Investigators in Hong Kong recently conducted two clinical trials of imiquimod cream and seasonal inactivated influenza vaccine. One clinical trial enrolled elderly participants, and the other enrolled young adults. The imiquimod cream was generally well-tolerated, and elderly and young participants who applied the cream before vaccination generated significantly more robust immune responses than those in control groups who did not receive imiquimod. The immune-boosting properties of imiquimod could stretch the supply of H5N1 vaccines because fewer doses would be required to achieve sufficient immunity in recipients. This would allow more people to be vaccinated in an outbreak.

The first clinical trial participant was vaccinated on June 19, 2018, and investigators expect to have early study results by the end of the year.