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)
https://twitter.com/AaronRichterman/status/1348492463229562880 …
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2. Data from AZ vaccine chadox study is a mess, but they did weekly PCR screening and points in the same direction. https://www.thelancet.com/action/showPdf?pii=S0140-6736%2820%2932661-1 …pic.twitter.com/MSsQCKlUU4
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3. We aren't reinventing immunology and need to consider our priors based on experience with other vaccine-preventable infections.https://twitter.com/PaulSaxMD/status/1337149176832876544?s=20 …
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3b. Another thread from
@MonicaGandhi9 on thishttps://twitter.com/MonicaGandhi9/status/1347988651179798530?s=20 …
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3c. The interesting counterargument involves requirement of IgA for upper resp tract mucosal immunity (vs IgG to prevent LRT symptomatic disease). However, as
@leela_davies points out, IgG-generating vaccines prevent transmission in other resp viruseshttps://twitter.com/SanjatKanjilal/status/1348544271310331909?s=20 …Show this thread -
4. Even if we assume vaccines ONLY prevent symptomatic disease, turning all into asymptomatic infections, there is a solid body of evidence
(inc systematic reviews from @mugecevik and@nicolamlow) that this alone would substantially reduce transmissionhttps://twitter.com/AaronRichterman/status/1340285330428182529?s=20 …
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5. Based on this, I think the possibility that these vaccines don't meaningfully reduce transmission (to the point that populations can move back towards normal life in due course) is low enough that we should treat this as a mostly theoretical concern at this point.
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6. An enduring lesson of this pandemic (& others) is the need to communicate uncertainty honestly (in both directions). Of course its reasonable to be careful, but lets not forget that this theoretical concern is being cited as a reason not to get the vaxhttps://twitter.com/AaronRichterman/status/1348494121019826178?s=20 …
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7. implications of monoclonal post-exposure prophylaxis data on transmissionhttps://twitter.com/EricMeyerowitz/status/1354231883190722571?s=20 …
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8. More on why reducing symptoms/severity w vaccines will probably reduce transmissionhttps://twitter.com/AaronRichterman/status/1351548094710652928?s=20 …
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8a. (Aside - Good paper with biases to be mindful of when comparing secondary attack rates of symptom/asymptomatic in households (page 19). h/t
@mugecevik) https://dash.harvard.edu/handle/1/37366192 …pic.twitter.com/ez5IssUk0F
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9. Some more discussion on Moderna dose 2 testinghttps://twitter.com/AaronRichterman/status/1350591945702318083 …
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10. Implications from regular pcr monitoring after natural infection. Less infections, lower viral load, more asymptomatic. Will reduce transmission. https://twitter.com/dylanhmorris/status/1357003968208121861 …
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10a. That said, similar caveats as below re whether those were even all reinfections.https://twitter.com/AaronRichterman/status/1355567294882131972 …
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11. More data from the Oxford/az randomized clinical trial. Vaccinated ppl who developed infection had lower viral loads and were pcr+ for one week shorter time relative to placebo. True for both asymptomatic and symptomatic cases. =>reduced transmission https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3779160 …pic.twitter.com/NsnUzCmrZk
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12a. And real world data from Israel. Interesting analysis inferring vaccine status by age and following cycle thresholds over time, suggesting lower VL in vaccinees w infection. Cool time series. Caveat: unclear what symptom status is but assume mostly symptom prompted testing.https://twitter.com/erlichya/status/1358477762495930368 …
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12b. Here are the pre-prints from the two real-world Israel studies of time series w viral load reduction after mrna vaccination. Some limitations including unknown symptom status, but suggestive. https://www.medrxiv.org/content/10.1101/2021.02.08.21251329v1 … https://www.medrxiv.org/content/10.1101/2021.02.06.21251283v1 …pic.twitter.com/z7yOhh6GPi
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13. Nice study of healthcare workers after Pfizer vaccine with regular PCR screening every 2 weeks. They found 70% reduction in all infections (asx or sx) dose1+3wks, 85% dose2+1wk. May be overestimated if vaccine
duration of pcr+, but expect large transmission
pic.twitter.com/okdA1wLh0U
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13a. Link for that last study: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3790399 …
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14. 75% protection against asymptomatic seroconversion in J&J vaccine trial.https://twitter.com/AaronRichterman/status/1364575515978440708 …
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14a. Important for those worried about b1.351. While this prelim analysis of asymptomatic infection after j&j is based on 29% completed serology data, most of the serologies from South Africa had been done.pic.twitter.com/PeFLn5jhbT
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15. No posted pre print yet but if this holds we now have 3 lines of evidence suggesting 85-90% reduction in all infections by the mrna vaccines (moderna RCT, Pfizer UK regular screening healthcare workers,
Israel regular screening).
H/t @EricMeyerowitzhttps://twitter.com/segal_eran/status/1365263943229452289 …
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15a. There is a little separation in the first few days so will need to see what kind of adjustment has been made here.
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16. On interpreting cross-sectional pcr during vaccine trials (i.e. moderna asymptomatic swabs at the time of dose 2) https://twitter.com/mlipsitch/status/1366172405119541250?s=20 …pic.twitter.com/7aHfqRYV5N
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17. Another study with regular (weekly) asymptomatic screening of hcw finds large reduction in pcr+ after Pfizer vaccine. The case for a large transmission reduction w vaccine seems closed at this point but will keep collecting these for now.https://www.authorea.com/users/332778/articles/509881-single-dose-bnt162b2-vaccine-protects-against-asymptomatic-sars-cov-2-infection …
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17a. At least until these stop coming on a daily basis... https://www.nytimes.com/live/2021/03/04/world/covid-19-coronavirus/its-unclear-how-easily-vaccinated-people-may-spread-the-virus-until-the-answer-arrives-scientists-urge-caution … https://www.google.com/amp/s/www.wired.com/story/we-still-dont-know-how-well-covid-vaccines-stop-transmission/amp …
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18. Neutralizing antibodies (like those induced by vaccines) reduce infection by 50% overall and in those who become infected there are fewer symptoms, lower viral load peak, shorter infections ~> large reductions in transmissionhttps://twitter.com/drlaurajwaters/status/1369328999944568836 …
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19. Interesting study of pre-procedural asymptomatic cov2 pcr screening - 80% reduction (95% CI 56-91%) in asymptomatic infection after both doses of mrna vaccines. Similar reduction after a single dose.https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciab229/6167855 …
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20. First observational study of household members of healthcare workers receiving mostly pfizer vax. After adjustment, 54% reduction in risk for household members (95% CI 30-70%) after both vaccine doses +14d in hcw. H/t
@mugecevik https://github.com/ChronicDiseaseEpi/hcw/blob/master/vaccine_manuscript.pdf …pic.twitter.com/izXumhKISL
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20a. Remember that this is not a contact tracing study and so reduction can be thought of as lower bound from the vaccinated household member since exposures may have occurred elsewhere
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: we know the age of the person and the date of the test. Since vaccination was started with 60+, we can compare the average Ct value positives in this age group as a function of time and compare to 40-60 as a control. Here are the results:
[Red: 60+;Blue:40-60]