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 They conclude the following in their paper that has been posted on a pre-print server (but has not yet been peer-reviewed):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.

______

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.

.