Thread by @MonicaGandhi9

Let's put data on why vaccines reduce transmission all in 1 place: Beyond sheer biological plausibility that vaccine-mediated immune responses block viral replication in nose, through which you are most likely to spread the virus, as effectively as blocks elsewhere, data here:

Lancet preprint showed that health-care workers in UK swabbed every two weeks after vaccination had an 86% reduction in asymptomatic infection compared with unvaccinated individuals: papers.ssrn.com/sol3/papers.cf…

Other data in Lancet - health care workers vaccinated had 85% reduction in infection (asymptomatic & symptomatic) 15-28 days after 2nd dose
thelancet.com/journals/lance…

Same data among health care workers in Mayo Clinic system (thanks for publishing this so fast!) showing reduction of 88.7% of symptomatic and asymptomatic infection after vaccination: medrxiv.org/content/10.110…

Study from Israel across a more general population (not health care workers) showed same finding of 92% reduction in ANY infection, even asymptomatic, with 2-dose vaccination:
nejm.org/doi/10.1056/NE…

Johnson & Johnson FDA data told us asymptomatic infection reduced by 74.2% after their 1-dose (you can tell if someone was infected by looking at nucleocapsid seroconversion instead of spike protein + asypmptomatic swabbing): fda.gov/media/146217/d…

Finally, 2 papers swabbed noses after vaccination (Israel, Pfizer), found - even if you are exposed and try to set up viral loads in your nose, nasal replication stopped early and you have low RNA, non-infectious. Be convinced!
medrxiv.org/content/10.110…
medrxiv.org/content/10.110…

I gave you real-world data above. There is also table S18 in supplementary material of Moderna NEJM study that shows asymptomatic infection reduced by 62% and AstraZeneca paper showing asymptomatic reduced. Papers here:
papers.ssrn.com/sol3/papers.cf…
nejm.org/doi/full/10.10…

if okay (#covid19) I am going to add on all studies that show
vaccines block transmission onto the same thread so you have them in one place (hope this works, added to prior thread). Here is another nice study! authorea.com/users/332778/a…

Took HCWs UK as they were getting vaccinated & did asymptomatic swabbing: 4,408 (week 1) & 4,411 (week 2) PCR tests performed in HCWS "reporting well to work". Stratified analysis <12 days or >12 days post-vax since this was point when protection from symptomatic infection began

#covid19, Study showed 4-fold decrease in risk of asymptomatic SARS-CoV-2 amongst HCWs ≥12 days post-vaccination, and if you had asymptomatic COVID-19, lower viral loads. This real-world evidence verifies high level of protection against asymptomatic COVID-19 after SINGLE

dose of Pfizer vaccine and (gasp), this is happening despite predominant transmission of B117 variant and in a population with low frequency of prior infection. So, do I call this #vaxtransmission to indicate that more evidence on top of the string of papers before?

Losing track, but this is 8th paper that vaccines reduce transmission so trying to add it to previous thread. We asymptomatically screen people who come to hospital or need surgery for infection control purposes- did asymptomatic infection decrease academic.oup.com/cid/advance-ar…

after vaccination? Aymptomatic adult patients (n = 39,156) within large US health care system who underwent 48,333 pre-procedural SARS-CoV-2 PCR tests between 12/17/20-2/8/21. Primary exposure of interest was vaccination with at least 1 dose of an mRNA vaccine, so asymptomatic

infection compared to those vaccinated vs those not. Positive PCR tests in 42 (1.4%) of 3,006 tests performed on vaccinated patients and 1,436 (3.2%) of 45,327 tests performed on unvaccinated patients. Compared to unvaccinated patients, risk of asymptomatic SARS-CoV-2

infection lower among those >10 days after 1st dose (RR=0.21) and >0 days after 2nd dose (RR=0.20 ) in the adjusted analysis. So, even after 1 dose of vaccine, 80% reduction in asymptomatic infection. Multiple papers show this from real-world studies, let's start incorporating

One more study (9th) on how vaccines reduce transmission. This press release from Pfizer Israel Ministry of Health data shows 94% reduction in asymptomatic infection from 1/17/21-3/6/21 after 2 doses of vaccine in general population. Are we convinced yet?
pfizer.com/news/press-rel…

Many studies that show this reduction in asymptomatic infection with vaccines, but, importantly, many studies showing a major reduction in viral load if you DO swab asymptomatic people after vax

And this thread goes over the studies that show reduction in viral load if you do swab those who are asymptomatic (or even symptomatic) after vaccination, which is why CDC doesn't rec testing asymptomatic after vax (different than asymptomatic before vax)