Am I the only one who doesn’t understand the Moderna Efficacy Table you screencapped?
39/1079 is an infection rate of 3.61% (They have 96.7%, which I assume means virus free? But that doesn’t match)
They say 7 out of 996 got infected who got one dose of the vaccine. That’s an infection rate of 0.703%. 0.703% / 3.61% = 19.4%, which I would call an 80.6% “effective” vaccine. They show a percentage of 87.5%?
None of this really matters, I guess, because the overall point is the same. Obviously one dose is ~pretty effective for varying definitions of “pretty”. But it’s still not clear to me what kind of math they’re doing.
It’s also worth looking at the next table for Moderna one-dose severe-COVID-prevention efficacy: Vaccine group: 2 / 996 Control group: 4 / 1079 Efficacy: 42.6% (-300.8, 94.8) [95% CI]
Huge error bars and little data, but certainly doesn’t support a guess of ~80% efficacy at preventing severe cases. In the end it’s the transmission that matters, but I suppose there’s a danger based on public perception: if one dose turns out to have under 50% efficacy for severe cases it’s not going to make anyone feel safe. If the sub 50% applies to deaths too, then you’ll have many reports of “X took the vaccine, caught Covid and then died”. I assume Moderna wouldn’t be crazy about this either. Not great PR if everyone broadly remembers that vaccines stopped Covid, but specifically remembers that Moderna’s failed to save their friend’s granny.
While there’s short supply, it doesn’t particularly matter if a load of people don’t want to take it. Once there’s a large supply, that changes—and if there’s a largely baked-in misperception that the vaccine(s) suck(s), it’s likely to be unhelpful.
In some sense it’s analogous to the mask situation: [Take action likely to reduce confidence in X] ---> [Free up supply of X to allow efficient targeting] ---> [Suffer consequences of longer-term low confidence in X]
Here the confidence-reducing action wouldn’t be a lie, but that’s not the only consideration.
My best guess on that table, looking at the full report (caveat: I am emphatically not an expert): 1) The VE calculations look correct: they’re almost precisely what I get by division of my naïve incidence rate calculations. I assume the small discrepancy is due to the data’s being discrete: if you have 7 cases out of 996, your best prediction of incidence rates won’t be precisely 7⁄996.
2) From my guess the numbers in brackets in the first two columns aren’t percentage rates at all. Rather they are “Surveillance time in person years for given endpoint across all participants within each group at risk for the endpoint”. This description is at the bottom of the table, without any asterisk or similar. I assume that this is an error: there was supposed to be an asterisk for that from the bracketed number in the first two columns.
This seems plausible for the data: the pre-14-days numbers are under half of the post-14-days numbers, and the median follow-up time was 28 days. But it’s entirely possible that I’m wrong.
Ah yes, I think you’re right. To me it seems that one dose efficacy is approx 80% from that table, and the two dose is still the old approx 95%. So it’s more like an 80% to 95% upgrade than 87% to 97%.
Zvi’s main point likely still stands, but the personal immunity question is less clear [ETA even on a population level it’s somewhat less clear, once you consider the confidence intervals: given 55% to 92% CI, one-shot efficacy could turn out to be below 70%, in which case things depend a lot on the homogeneity of populations, the precision of your targeting, and post vaccination behaviour changes]
I was responding to other people saying what the numbers were and didn’t attempt to read the chart in detail—it was more ‘oh grab the primary source and that looks about right’ because as usual things move quickly.
But yes, the first dose being much more than half the total is all it takes to draw the same conclusion.
Am I the only one who doesn’t understand the Moderna Efficacy Table you screencapped?
39/1079 is an infection rate of 3.61% (They have 96.7%, which I assume means virus free? But that doesn’t match)
They say 7 out of 996 got infected who got one dose of the vaccine. That’s an infection rate of 0.703%. 0.703% / 3.61% = 19.4%, which I would call an 80.6% “effective” vaccine. They show a percentage of 87.5%?
None of this really matters, I guess, because the overall point is the same. Obviously one dose is ~pretty effective for varying definitions of “pretty”. But it’s still not clear to me what kind of math they’re doing.
It’s also worth looking at the next table for Moderna one-dose severe-COVID-prevention efficacy:
Vaccine group: 2 / 996
Control group: 4 / 1079
Efficacy: 42.6% (-300.8, 94.8) [95% CI]
Huge error bars and little data, but certainly doesn’t support a guess of ~80% efficacy at preventing severe cases. In the end it’s the transmission that matters, but I suppose there’s a danger based on public perception: if one dose turns out to have under 50% efficacy for severe cases it’s not going to make anyone feel safe. If the sub 50% applies to deaths too, then you’ll have many reports of “X took the vaccine, caught Covid and then died”.
I assume Moderna wouldn’t be crazy about this either. Not great PR if everyone broadly remembers that vaccines stopped Covid, but specifically remembers that Moderna’s failed to save their friend’s granny.
While there’s short supply, it doesn’t particularly matter if a load of people don’t want to take it. Once there’s a large supply, that changes—and if there’s a largely baked-in misperception that the vaccine(s) suck(s), it’s likely to be unhelpful.
In some sense it’s analogous to the mask situation:
[Take action likely to reduce confidence in X] ---> [Free up supply of X to allow efficient targeting] ---> [Suffer consequences of longer-term low confidence in X]
Here the confidence-reducing action wouldn’t be a lie, but that’s not the only consideration.
My best guess on that table, looking at the full report (caveat: I am emphatically not an expert):
1) The VE calculations look correct: they’re almost precisely what I get by division of my naïve incidence rate calculations. I assume the small discrepancy is due to the data’s being discrete: if you have 7 cases out of 996, your best prediction of incidence rates won’t be precisely 7⁄996.
2) From my guess the numbers in brackets in the first two columns aren’t percentage rates at all. Rather they are “Surveillance time in person years for given endpoint across all participants within each group at risk for the endpoint”. This description is at the bottom of the table, without any asterisk or similar. I assume that this is an error: there was supposed to be an asterisk for that from the bracketed number in the first two columns.
This seems plausible for the data: the pre-14-days numbers are under half of the post-14-days numbers, and the median follow-up time was 28 days.
But it’s entirely possible that I’m wrong.
I’m having trouble with it too and I think Zvi misinterpreted it as well- the far right column is the VE.
Ah yes, I think you’re right.
To me it seems that one dose efficacy is approx 80% from that table, and the two dose is still the old approx 95%. So it’s more like an 80% to 95% upgrade than 87% to 97%.
Zvi’s main point likely still stands, but the personal immunity question is less clear [ETA even on a population level it’s somewhat less clear, once you consider the confidence intervals: given 55% to 92% CI, one-shot efficacy could turn out to be below 70%, in which case things depend a lot on the homogeneity of populations, the precision of your targeting, and post vaccination behaviour changes]
I was responding to other people saying what the numbers were and didn’t attempt to read the chart in detail—it was more ‘oh grab the primary source and that looks about right’ because as usual things move quickly.
But yes, the first dose being much more than half the total is all it takes to draw the same conclusion.