Large contact tracing study in UK shows Pfizer vaccine reduces transmission by 82% vs alpha and 65% vs delta and AstraZeneca by 63% and 36%, respectively. medrxiv.org/content/10.110…
The study uses the national contacting tracing registry and compares testing positivity of contacts across vaccinated and unvaccinated, stratify information by vaccine type and number of doses
The modeling accounts for key potential confounding variables in the tested individual so as not to be driven by demographic factors.
Besides main results they also look at other secondary factors, demonstrating vaccine protection vs transmission is attenuated w/ delta relative to alpha & wanes over time since vaccination.
It also validates that those with low Ct at time of testing are more likely to transmit
It also validates that those with low Ct at time of testing are more likely to transmit
Overall, a well done study, and demonstrates the naivety of assuming that just because Ct are just as high in breakthrough delta infections as unvaccinated delta infections that no protection vs transmission is retained.
The vaccines have a great benefit for the vaccinated in significantly reducing risk of severe disease or death from covid.
But they also benefit those around the vaccinated person by reducing their probability of transmission if infected, even with delta and even after waning
But they also benefit those around the vaccinated person by reducing their probability of transmission if infected, even with delta and even after waning
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