Thread by @MonicaGandhi9

Thread on transmission after vaccination without references since put in my previous thread- we may be determining our ideas on transmission after vax from rotavirus & other viruses without looking at unique features of SARS-CoV-2 & all the real world data we have:

While the clinical trials for the vaccines were not designed to assess whether vaccines reduced asymptomatic infection (and, thereby, transmission), there is biological plausibility that the antibodies and T-cell responses blocking symptomatic disease will also block asymptomatic

infection in the nasal passages. IgG immunoglobulins (generated and measured by the vaccine trials) enter the nasal mucosa. Moreover, SARS-CoV-2 vaccines also generate IgA (immunoglobulins at mucosa surface) which protect nasal passages from infection
researchsquare.com/article/rs-310…

Accumulating data from the real-world roll-out has also shown us vaccines reduce transmission. We tweeted these before- health-care workers in the United Kingdom who were swabbed every two weeks after vaccination demonstrated an 86 percent reduction in asymptomatic infection

compared with unvaccinated individuals. Health-care workers in Israel and across the Mayo Clinic system, show a similar result: a massive reduction in both symptomatic disease and asymptomatic infection after vaccination. A study from Israel with Ministry of Health data

showed that asymptomatic infection was reduced by 94% after two doses of the Pfizer vaccine (press release 3/11/21). A large study from vaccinated patients presenting for pre-surgical care at Mayo Clinics compared to unvaccinated showed an 80% reduction in asymptomatic infection

following mRNA vaccines. Another study from vaccinated HCWs in the UK show a four-fold reduction in asymptomatic infection with routine swabbing compared to unvaccinated HCWs after just 1 dose of the mRNA vaccine. Now, if you get exposed after vaccination, what are chances

you could be infectious to others? Nasal viral loads from post-vaccination exposures are low per two papers and likely noninfectious per CT values. Given that low nasal viral loads are the most important predictor of ability to transmit infection
thelancet.com/journals/lanin…

these lower nasal SARS-CoV-2 RNA levels in those vaccinated versus those unvaccinated portends well that forward transmission after vaccination will be rare. Therefore, asymptomatic surveillance testing after vaccination not indicated (which is why CDC said only quarantine after

exposure once vaccinated if you are symptomatic). And if you are exposed and testing indicated, would suggest rapid antigen test not PCR test as your viral load in nose could be low and not infectious given data above. academic.oup.com/cid/advance-ar…

WHAT SHOULD WE DO REGARDING TESTING AFTER VACCINATION? I wanted to add this query about testing on to this thread regarding transmission or asymptomatic infection after vaccination sine they are related. I have 2 threads on transmission reduction after vax - will try to merge

Based on CDC guidelines no need to quarantine after vax if asymptomatic & exposed, rec:
1) No asymptomatic surveillance after vaccination for COVID if exposed
2) If symptomatic, test but start with rapid antigen test to see if infectious
3) If positive on rapid, sequence strain

TRANSMISSION AFTER VACCINATION THREAD: Trying to add on to the same thread here about low rates of infection after vaccination (yes, even asymptomatic) since two new papers from NEJM today are relevant. We start with this table; many studies to date in real-world vaccines

massively decrease asymptomatic infection (which of course means reduce transmission). Implications: 1) vaccinated being around unvaccinated; 2) testing after vaccination if asymptomatic and whether public health resources should be used for that.1st paper
nejm.org/doi/full/10.10…

1st paper from University of Texas Southwestern Medical Center (UTSW). After vaccination, very difficult to get infected, figure here. % of persons who became infected differed according to vaccination status: infections in 234 of 8969 nonvaccinated employees (2.61%), 112 of 6144

partially vaccinated employees (1.82%) & 4 of 8121 fully vaccinated employees (0.05%). Gives credence to CDC rec that health care workers need not quarantine after exposure if asymptomatic (and low chance of COVID-19 even if symptomatic). 2nd paper
nejm.org/doi/full/10.10…

During surge in Southern California among HCWs while getting vaccine. Rare to test positive (asymptomatic swabs) after 2nd dose of vaccine (7/4167) 0.01% so even during surge with exposure (HCWs), hard to test positive after vaccination meaning very protective vaccine.