Friday, February 26, 2021

Direct Assessment Of Asymptomatic Subjects Suggests That Pfizer Vaccine Decreases Viral Transmission.

Methodology
CountsVille


A group from Cambridge in the UK directly determined the presence or absence of SARS-CoV-2 virus, by PCR test, of health care workers (HCWs) in Cambridge that either had been or had not been dosed, one time, with the Pfizer mRNA vaccine (BnT162b2). They conclude the following in their paper that has been posted on a pre-print server (but has not yet been peer-reviewed):

...26/3,252 (0·80%) tests from unvaccinated HCWs were positive (Ct<36), compared to 13/3,535 (0·37%) from HCWs <12 days post-vaccination and 4/1,989 (0·20%) tests from HCWs ≥12 days post-vaccination (p=0·023 and p=0·004, respectively; Fisher’s exact test, Figure). This suggests a four-fold decrease in the risk of asymptomatic SARS-CoV-2 infection amongst HCWs ≥12 days post-vaccination, compared to unvaccinated HCWs, with an intermediate effect amongst HCWs <12 days post-vaccination...

{snip}

...We therefore provide real-world evidence for a high level of protection against asymptomatic SARS-CoV-2 infection after a single dose of BNT162b2 vaccine, at a time of predominant transmission of the UK COVID-19 variant of concern 202012/01 (lineage B.1.1.7), and amongst a population with a relatively low frequency of prior infection (7.2% antibody positive)...


This is a big deal and, assuming that everything was done properly as will be determined by expert peer reviewers, it strongly suggests that a single shot of this vaccine significantly decreases viral transmission in otherwise healthy subjects in addition to preventing folks from getting sick once they have been infected with the virus (which is what was originally tested in the clinical trials and has since been confirmed in Israel). 

I'm noting this here, based on a pre-print, given that I've fussed previously here and here about potential over interpretation by some, including some proMedia, of previous studies where viral transmission in all asymptomatic subjects was not directly tested.



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Note that this study was done at a time when the UK variant (lineage B.1.1.7) was already known to be prevalent in Britain, which is another good thing...For the PCR aficionados out there, the authors found significant differences between the unvaccinated and vaccinated subjects with Ct values of less than and greater than 36...
Here in BC, this is further good news for our initial one shot strategy for folks in long term care where the vaccination rate is already very high.



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4 comments:

Graham said...

Thanks again for passing on the interesting and informative stuff. I’m still reading, passing it on and mostly understanding at the street level. I know you mentioned that this isn’t your area of expertise as well but your background is certainly more suited than most.
You’re the most sciency guy I don’t know, or know, kinda, in a blog sort of way.
You must be plowing through a lot of reading and tweets and reports and journals etc to glean all this.
Mostly it’s sounding like guarded good news on the vaccine front so... cheers.

Anonymous said...

Making sense of the world today is no easy task for those who’ve yet to abandon the standard American diet of propaganda and mental programming. Indoctrination works in a couple of key ways. Firstly, beliefs are instilled and reinforced by repetition, and secondly, undesirable beliefs are ignored and cast aside as fringe. What’s left is a mind which focuses on what it’s supposed to focus on, constructing a reality around a false and incomplete picture of the world.

e.a.f. said...

Really liked the headline! Even read the science article. Informative.

I'm not a science person at all. You do make it easy even for people who were in the Arts faculty as students to understand this.

Anything which will slow transmission is going to be a gift. Anything which will reduce the effects of the disease is a gift. As long as people stop dying.

Read the J. & J. vaccine has a 60% "success rate". I'm good with that and if offered that shot, I'd take it in a heart beat because I'm not waiting for `100% of anything. Now we just need people to take those shots.

Read something yesterday which informed that 1/3 of the american military wasn't interested in taking the shots. That does not bode well for any one.

RossK said...

Graham--

Keeping up with and plowing through life science stuff, in another context, is a good chunk of my day job.

For the vaccine stuff, there are a number of true experts commenting on-line, in close to real time, that are very helpful in identifying key developments.

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Anon-above--

In my opinion a lot of the problematic stuff in the proMedia, and it's not universally a USian issue, is driven by the need to keep the news cycle wheel turning.

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Thanks, as always e.a.f.--

Glad to hear you had a look at the paper.


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