Influenza viruses are commonly used in human challenge studies.
Both the viruses and the disease they cause are well understood,
and the induced illness is short-lasting. It is becoming increasingly
diffi cult to gain FDA approval for a disease-preventing vaccine or an
anti-infective drug purely on the basis of biomarker studies. In this
article, Adrian Wildfi re, SGS Infectious Diseases project director,
explains that proof of real-world effi cacy is required, therefore a
challenge trial will give an indication of how eff ectively the vaccine
is preventing infection, or the drug is improving the symptoms of
the disease.