The Covid-19 vaccine trial designed by Pfizer and its German partner BioNTech may allow them to find whether their shot works before their fastest moving rivals.
The companies plan a first look after a mere 32 coronavirus infections have accumulated in their 44,000-person trial.
That case total could be reached as soon as September 27, according to Airfinity, a London-based analytics firms tracking vaccine trials.
Pfizer has also given itself four chances to get a preliminary result, before reaching the final goal of 164. Some trial experts say the company appears to be looking for a leg up in a race against frontrunners such as Moderna and AstraZeneca to be first with a vaccine.
“I’ve never seen a trial where there were four interim analyses; that may be the Olympic record,” said Eric Topol, editor-in-chief of Medscape, a website offering clinical information for health-care professionals, and director of the Scripps Research Translational Institute.
A wide range of symptoms and severity makes the evaluation of Covid-19 vaccines tricky. The US Food and Drug Administration has said that to be approved, vaccines should cut the number of symptomatic cases by half.
Yet documents released by the drugmakers show each has its own approach to defining which symptoms count, and when to count them.
Big drug studies usually allow a panel of monitors to get an early peek at the data once or twice before the planned end.
The panel can stop the trial early if a treatment is judged overwhelmingly effective — or a total dud.
The issue is gaining attention as questions persist about the halt of AstraZeneca’s human tests in the US following the appearance of side-effects that Oxford said were unlikely to be linked to the vaccine.
Moderna, working with the US National Institute of Allergy and Infectious Diseases, won’t dive in until 53 cases have occurred.
Its ultimate goal is to make a judgment at 151 diagnoses.
Cancer powerhouse AstraZeneca, collaborating with the University of Oxford, will take its first look at 75 cases, and not again until the trial is complete with 150.
“All trials have set the bar quite low for what they test against,” said Airfinity chief executive Rasmus Bech Hansen.
Pfizer’s trial was designed to evaluate its vaccine candidate “as fast as possible", said spokeswoman Amy Rose.