This is the key observation that somehow has not really made it outside of hospital circles. Still waiting for the first detailed report from a large health system of in-hospital transmissions in the universal masking era. Per hospital epis I’ve spoken with close to 0
This Lancet report gets highly referenced suggesting healthcare workers higher risk but 1) much of it pre-universal masking 2) don’t report whether community acquired (much of it is per other publications from healthcare) 3) no contact tracing
This paper of 226 patient contacts of healthcare workers w CoV2 (both pre and post universal masking) is probably the best 1 on the subject — they found one possible transmission, during a 30 minute encounter w both patient and healthcare worker unmasked
This paper is another important piece to this, but would still like to see how this change in high risk exposures translates to numbers of linked transmissions
And now: published yesterday in @JAMANetworkOpen, out of 9000+ patients admitted during Boston surge in universal masking era, TWO hospital acquired cases in patients, both w explanations
Obviously there are additional precautions for patients so some caveats to generalization — why I would like to see this amount of detail about healthcare worker infections
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We used >80 national surveys in 37 low- and middle-income countries to create longitudinal survival datasets for 4 million adults & 3 million children 2000-2019
About 1/2 the countries started cash transfer programs, & 1/2 the programs were unconditional (no strings attached) /2
We used difference-in-difference models to show these programs led to a 20% reduction in mortality for women, and an 8% reduction in risk of death for children under 5
/3
First, to review, vaccines can provide:
-direct protection (reduction in infx/disease among vaccinated ppl)
-indirect protection (reduction in infection among all community members through ⬇️ transmission)
/2 nature.com/articles/s4157…
Indirect protection can be generated by 1) ⬇️ risk of infection (if person not infected, cannot transmit) 2) ⬇️ infectiousness of vaccinated person w infection
As @mugecevik points out, despite the recent proliferation of vaccine studies using routinely collected testing data, the majority of these cannot be reliably be used to estimate VE vs all infections because they do not use systematic testing and/or control for confounding.
Vaccine protection against all infections is one important way (of several) that vaccines reduce transmission (discussed👇). Here is an updated table of high-quality studies assessing VE against infection, including just 3 from the delta era at the bottom academic.oup.com/ofid/advance-a…
When using regular (or cross-sectional) systematic testing to estimate VE, you are really measuring VE against a composite of infection and duration of PCR-positivity, as highlighted recently by @dylanhmorris.
Fascinating discussion of these methods here sciencedirect.com/science/articl…
This 👇claim arises principally from Israeli data (which is unpublished in any form so will withhold judgment) and from the UK REACT 1 study, rounds 12 & 13. But... is the REACT 1 data likely to be solely explained by delta? 🧵
(study link spiral.imperial.ac.uk/handle/10044/1…)
This is the table in question. You can see VE of a combination of AZ/MRNA vs symptomatic infection was 83% (19-97%) in round 12, but only 59% (23-78%) in round 13. The concern of course is that this drop in VE is due to delta, which had completely taken over by round 13 /2
However, while 100% of the isolates identified in round 13 were delta, 80% in round 12 were also delta (20% were alpha). Any effect of delta on VE should have been partially seen in round 12. /3
The question at hand: what is the relative transmission potential of a vaccinated person who becomes infected with delta? This 👇new report from Singapore is much more informative on this question than the CT data released so far from Ptown and Wisconsin. medrxiv.org/content/10.110…
First, importantly, reducing transmission potential of a person who becomes infected is only one component on the transmission reduction effect of the vaccines. The other: reducing the likelihood of becoming infected in the first place. We discuss here👇 academic.oup.com/ofid/advance-a…
We still await definitive evidence from systematic sampling on the ? of overall infection risk reduction with vaccination, but w strong protection vs symptomatic disease, expect that there will still be substantial protection (50+%) vs overall infection nejm.org/doi/full/10.10…
Interesting poll. Selection/response bias aside, majority picked a low probability, but 40% still thought there was 10+% prob that vaccines will not substantially prevent transmission. This is why I have become convinced this concern is highly unlikely (borderline implausible) 🧵
1. Data from screening PCR at the time of the 2nd moderna mrna vaccine, showing reductions in asymptomatic PCR positivity. This is before the 2nd dose and if anything will underestimate effect. Will have additional confirmation from unblinding pcr and ab