“We now have the official clinical trial designs for the three biggest and most advanced coronavirus vaccine trials: Moderna, Pfizer/BioNTech and Oxford/AstraZeneca. Now, as for you, J&J, Novavax, Merck, and all the others that are pushing into efficacy trials as fast as possible – don’t think for a moment that you won’t be expected to do the same. But this is a good start. So how do these trials differ?”
“Let’s start off with some background, starting with “vaccine efficacy” (VE), which is pretty much what it sounds like: the percentage difference of infection by the virus between the vaccinated group and the unvaccinated control group. The FDA has already said that they want to see 50% at least (i.e., the vaccine cuts the rate of coronavirus infection at least in half). All of these trials have different subgroups, especially broken out by age and/or pre-existing conditions, and there will be not only an overall VE for the trial but separate VEs determined for all of the predefined subgroups. As is standard, the trials will be using what’s called a Cox proportional hazard regression model to assess the differences between the various groups – I won’t go into the details here, but that’s how you get the eventual figures of “Group A is 2.1x less likely to get infected than Group B” and so on. The Cox model actually gives you the “hazard ratio” (HR) which is just the opposite of the VE, so a 60% HR would mean a 40% VE.”
Medicynical note: the companies’ plans sound fine if they stick to them. The Russians And Chinese are prematurely, IMHO, marketing their not fully tested vaccines around the world. Their reach may be making these companies nervous as does the ignorant political prodding from Trump.