October 21, 2013
Those unfortunate infections are not surprising.
There isn't much protection during the first 14 days after the first shot. Those 90%+ efficacy numbers one sees are from 14 days after the second shot.
Page 28 of the FDA briefing document for the Moderna vaccine indicate around 50% efficacy over the 14 days after the first shot.
Unfortunately, that information isn't really relevant.
1. There is no age breakdown between 65 and 95, a huge gap, so we don't know if works better for 65 than 95. And my personal concern is with 99+, which was never studied.
2. The cases I'm looking at were 21 days after dose 1, not 14.
3. I didn't actually find anything relevant when I searched "14 days after first dose", but perhaps it's hiding there somewhere.
However, even if we assume 50% efficacy after 2 weeks, and assume perhaps 55-60% after 3 weeks, and we assume efficacy is the same for 65 yrs as it is for 95 or 100 yrs (highly unlikely in my opinion), and we assume there is some statistical significance to what I have observed (which there may not be), then it appears to suggest that, without the first dose vaccine, the infection rate would have been about twice as high. This may be a good sign for the efficacy of the vaccine but it also suggests that the virus is becoming a more difficult enemy. The incidence range in this facility is in the same per capita range after 21 days as it was without any vaccine. In fact, this is as many infected residents as they've ever had at one time. Protocols have also changed several times.
It is hard to make comparisons. I was just raising the issue as something to watch. There are no definitive answers at this point to the questions I have raised, but the situation leaves me uneasy.
April 6, 2013
Unfortunately, one cannot draw precise conclusions from the situation and the data.
Testing is not precise. Detection on Day 21 does not mean infection on that day. The person could have been infected way before that.
As well, someone can be infected and not have enough virus in the area where the nasal swap collects to be detected. I think there was one university student who got sick. She was symptomatic yet her first COVID test came back negative.
That's not quite what the 50% number means. It means that during the first 14 days, the number of infected people who got the vaccine was 50% of the number who got the placebo. However, there is lots of statistical uncertainty with that 50% number because there was only a total of 16 infections: 5 from vaccine group and 11 from placebo group. That's not significantly different from an 8 and 8 split from an ineffective vaccine.
I think it is better to presume that there is little protection in the 14 days after the first shot.
The Ontario positivity rate is around 3.3% these days. So, a 3% infection rate in a nursing home is not that far off from that of the general population.
October 21, 2013
I agree that there are lots of problems making comparison.
There are always false positives and false negatives with any testing regimen, so that will remain regardless.
Not true though that the ~3% positivity rate for the public is comparable to a similar rate in a retirement home. The positivity rate for general public is related to which segment of the population took the test. While they all had to have a reason for taking it, few if any will have had any vaccine and only a minority are elderly. The ones in the retirement home are a control group in the sense that they all had had one dose of vaccine and they are probably all over 70 at least. (Median age is known to be 84 in this case. I've never seen anyone that old in a line-up for a test, and I've been in them several times. Most appear to be under 50.)
In this case, they all became positive later than 14 days and by 21 days, as they were being tested weekly, so the 14 day thing doesn't apply - as I tried to say before.
I don't think there is any point in belabouring this any further.
February 27, 2018
October 21, 2013
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