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Moderna & Pfizer vaccine first dose effectiveness

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    So I got to thinking about just how many people have only gotten the first dose of the vaccine. Whether it be Moderna, Pfizer or AstraZeneca (leaving Johnson & Johnson out since it's single-dose), the numbers are heavily in favor of most people only having their first dose so far. More and more are getting their second shot each day, but until you get your second shot you're not completely vaccinated just yet. With that being said, I looked into how effective only having the first dose is.

    I remember hearing that some wanted to split the second dose even longer to get more people their first doses in the U.S., but that idea was quickly shot down due to that's not how the vaccine was tested. It is however how the UK is handling it right now, splitting up the doses to get more their first shots. But now we have at least some data to show how effective one shot really is.

    It turns out that having just the first shot is a bit more effective than I thought. Stephen Evans, a professor of medical statistics at the London School of Hygiene and Tropical Medicine found that the first dose of the Pfizer vaccine is about 52% effective against symptoms. The Moderna vaccine sat around 69% effective, and the AstraZeneca shot was about 76% effective. All of these numbers came with many caveats though. For instance, the FDA said Pfizer's first dose effectivity was actually somewhere between 29% and 84%. The numbers vary so much because the test samples just aren't large enough yet to know any numbers for sure. So keep that in mind.

    Again, this is only from the data we have so far. I briefly looked into it and the current numbers just kind of surprised me. These things change and evolve overtime and eventually the facts become more clear. Make sure you get your second dose when you're supposed to.

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    Interesting. So is there any reasoning to why Moderna is more effective than Pfizer, for the first shot? Is this just an example of not enough sample size to get reliable data just yet? I would think they would be very very close in effectiveness, given the phase 3 test results being so close.
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    I'm surprised that they aren't closer as well. How does the Johnson and Johnson one stack up against the other two I wonder?
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    This article says the Public Health England determined the Pfizer vaccine to be 89% effective from the first shot. But the way it works is it starts off as 50%ish effective in the first several days but after 15-21 days becomes more and more effective as your body has had time to generate protective ant-spike antibodies.

    This makes sense to me and explains the variance gap. So really 52-89% from the first dose alone at least for Pfizer BUT you should definitely still get the second dose to make those numbers better AND to boost your response even greater.