Vaccines keep ppl out of hospital - their most important attribute
However, vax’d can be infected & transmit. Yes, vax slow spread but by no means does vax mean you can’t be infected & spread
This is critical to acknowledge as we try to limit Omicron spread
If public health officials fail to appreciate & acknowledge clearly that vaccinated can in fact acquire and spread the virus and that this is not rare, I fear ppl will continue to believe they can’t spread if they are vax’d and do less to limit spread of Omicron where it exists.
I am 100% for vaccination. I just want public health to be transparent about what vaccines do well and don’t do well so ppl are fully informed.
For too long messaging said transmission among vax was rare. This then caused confusion and loss in confidence in the vaccines.
Also,
This isn’t just about Omicron. This is about Delta too.
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🧵 Why some vaccines stop transmission & others don’t:
Vaccines that stop transmission are often against viruses that replicate internally first and only then transmit (like measles). So if the vaccine stops internal replication, it stops transmission.
For COVID vaccines…
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For vax against upper respiratory viruses like SARS2, these viruses often don’t require “internal” replication. They just land in the nose, replicate locally & transmit on. So the vax can block “internal” replication and thus stop disease separate from stopping transmission
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The immune response in the upper respiratory tract is somewhat distinct from response in lungs, blood, lymph, etc.
Most vaccines create a multitude of layers of protection that can block a pathogen in lungs, blood, lymph, without offering the same in the nose/mouth/throat
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The constellation of mutations suggest it is likely more immune evasive…
(but how much more is difficult to say - particularly with Vax plus the large number of exposures to Delta over the past 6+ months, our immune systems may be getting sufficiently trained)
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Many of the mutations that are accumulated have been seen among variants that have a more difficult time being neutralized by our immune response. And among variants that are more infectious.
🧵 When the goal is limiting transmission, timing of tests is everything
If you wait days for positive results before isolating, the time spent waiting must be factored in to the “effectiveness sensitivity” of a test.
Time is always ignored as a test metric. This is wrong
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If people are infectious for 6 days and you have to wait 2 days for results, then for every 3 positive people detected, you miss the equivalent of an entire infection Bc the sensitivity while waiting is 0%.
This means the “effective sensitivity” cannot break 67%. But worse…
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What’s particularly bad but also ignored is the **0% sensitivity** while awaiting a lab PCR result is for everyone - even people who are at absolute peak virus titers and immediate isolation is most important. For these people, rapid tests detect >95% - with immediate action
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When we say “pandemic of the unvaccinated”, it is stigmatizing & inaccurate - this is a pandemic of a virus that is disproportionately afflicting unvaccinated
I urge us to consider root causes of why so many are unvaccinated
🧵 When ppl give anecdotes about public health efforts not working - please proceed cautiously
It is rare that public health success makes headlines or goes viral Bc success in public health almost always represents the absence of anything interesting.
Bias is tough to spot
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Imagine for example if a vax failure in a single person was the only times vaccines made headlines. We’d think they didn’t work. But this is why we have trials - to ensure that we put any Vax failures into proper perspective and measure rates of success vs failure
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The same goes for anecdotes around tests, for example:
The White House Rose Garden outbreak made headlines and made everyone think that tests don’t work.
What was not discussed were the hundreds of WH events w no outbreaks owing exclusively in that WH to testing.
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