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Comment by vlovich123 | Hacker News Reader

I keep hearing this in this thread but I don’t follow.

> Based on evidence from clinical trials, in people ages 18 years and older, the Moderna COVID-19 vaccine was 94.1% effective at preventing laboratory-confirmed COVID-19 infection in people who received two doses and had no evidence of being previously infected.

If you’re prevent infection, aren’t you effectively reducing the R0 by definition? How is the vaccine making it harder to infect not reduce transmission rates?

[1] https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different...

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Yes, these are the original data from clinical studies. Now, in real life, a few months later the efficiency has dwindled considerably [0]:

> Reports of waning vaccine-induced immunity against COVID-19 have begun to surface. With that, the comparable long-term protection conferred by previous infection with SARS-CoV-2 remains unclear.

[0] https://www.medrxiv.org/content/10.1101/2021.08.24.21262415v...

"Remains unclear" is very different from "no impact on transmission rates". Here's the follow-up paper from the same group [1]

> These results suggest that the vaccine is initially effective in reducing infectiousness of breakthrough infections even with the Delta variant, and that while this protectiveness effect declines with time it can be restored, at least temporarily, with a booster vaccine.

The paper you're looking at is analyzing waning immunity against the Delta variant.

[1] https://www.medrxiv.org/content/10.1101/2021.08.29.21262798v...

> "Remains unclear" is very different from "no impact on transmission rates".

Well, at least within households[0]:

> Research reveals fully vaccinated people are just as likely to pass virus on to those they share a home with

[0] https://www.theguardian.com/world/2021/oct/28/covid-vaccinat...

The first sentence of the article is that it's about "People who are fully vaccinated against Covid yet catch the virus". If the vaccines don't lower P(transmission|infection) but do lower P(infection), then they lower P(infection & transmission) (because that's the product of those two).

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