I’m not sure about this statement in the blog post:
In the meantime, the single dose alone is 76% effective, presumably against symptomatic infection (WaPo) and was found to be 67% effective against further transmission.
I read another article saying that this is disputed by some experts:
Media reports seized on a reference in the paper from Oxford researchers that a single dose of the vaccine cut positive test results by 67%, pointing to it as the first evidence that a vaccine could prevent transmission of the virus. But the paper, which has not yet been peer-reviewed, does not prove or even claim that — although it hints at the possibility.
[...]
If a person tests negative, Andrew Pollard, one of the study authors and a professor of pediatric infection and immunity at the University of Oxford, told STAT via email, “then it is a reasonable assumption that they cannot transmit.”
But it is a big and unjustified leap, outside experts agree, from that suggestion to proof of decreased transmission from people who are vaccinated.
“The study showed a decrease in [viral] shedding, not ‘transmission,’” said Carlos del Rio, a professor of infectious diseases at the Emory University School of Medicine. “The bottom line is, no, one cannot draw a conclusion or straight line.”
Unfortunately the article doesn’t say specifically why these experts consider this an unreasonable inference while the study’s author thinks it’s a reasonable inference. The closest thing is “There are too many, in my view, moving variables.”
I can imagine one possibility for a counterintuitive result. Suppose the vaccine turns severe cases into asymptomatic cases, and transmissions happen mostly in asymptomatic cases?
Also, I was unable to tell from the paper when they do PCR+ tests. I have read that in some studies, they only do tests when a test subject shows symptoms, which would mean that some asymptomatic cases might be missed?
As a non-expert, I think we need to hedge our bets when experts disagree.
But there is something good to say about their data collection: since the UK study that’s included in these numbers tested its subjects by nasal swab every week, regardless of any symptoms, we can actually get a read on something that everyone’s been wondering about: transmission.
I’m not sure about this statement in the blog post:
I read another article saying that this is disputed by some experts:
[...]
Unfortunately the article doesn’t say specifically why these experts consider this an unreasonable inference while the study’s author thinks it’s a reasonable inference. The closest thing is “There are too many, in my view, moving variables.”
I can imagine one possibility for a counterintuitive result. Suppose the vaccine turns severe cases into asymptomatic cases, and transmissions happen mostly in asymptomatic cases?
Also, I was unable to tell from the paper when they do PCR+ tests. I have read that in some studies, they only do tests when a test subject shows symptoms, which would mean that some asymptomatic cases might be missed?
As a non-expert, I think we need to hedge our bets when experts disagree.
That piece seems like pure FUD and “no evidence” to me. I don’t think this is “experts disagree” in a meaningful way.
I found an answer on the PCR question here: