Both Pfizer and Moderna have announced recently that their SARS-COV2 vaccine candidates reduce the rate of infection by over 90% in the active group compared to the control (placebo) group.
That’s great news. The vaccines may turn out to be less than 90% effective when all is said and done, but even so they’re likely to be far more effective than expected.
But there’s other good news that might be overlooked: the subjects in the control groups did well too, though not as well as in the active groups.
The infection rate was around 0.4% in the Pfizer control group and around 0.6% in the Moderna control group.
There were 11 severe cases of COVID in the Moderna trial, out of 30,000 subjects, all in the control group.
There were 0 severe cases of COVID in the Pfizer trial in either group, out of 43,000 subjects.
I’ve been watching this closely, primarily from a stats perspective. What does it mean for me, and my tiny bubble, and my major risk factors (age, asthma)?
What it means is all good, especially with the Moderna level of disclosure and explanation. I always look at the downside stats, and Moderna has presented a great case, and though I lack access to the underlying data, the FDA concurrence thus far encourages me greatly.
With Moderna, I may get a sorta-flu, but it looks like I won’t get COVID!
Isn’t the fact that the subjects in the control groups did well too is worriying? For example, doesn’t it make the overall sampling procedure a bit dubious? I’d expect the control group to exhibit a similar distribution to that of the general population.
I don’t think so.
The control group probably does exhibit a similar distribution to the general population, at least that part of the population healthy enough to participate in the study. Most severe covid cases have been in people who I imagine are in too poor health to be eligible for the study.
Also, I suspect that when the study counts cases, they mean actual cases and not merely positive PCR tests. That is, they probably count people who are suffering from covid and not merely people who were found to have a virus particle in their nose. But it’s hard to say because all we have to go on at this point is news stories and not scientific papers.