Read on Twitter
"I don't want the AstraZeneca vaccine. It is only 62% effective. I want the Pfizer vaccine it is 95% effective."
A thread.
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@US_FDA
@DrEricDing https://twitter.com/walletnumb123/status/1348263632648462342
A thread.
1/n
@US_FDA
@DrEricDing https://twitter.com/walletnumb123/status/1348263632648462342
First, the statement above is the equivalent of comparing apples to oranges and an oversimplification of a complex situation.
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The way efficacy of vaccines is measured is not always the same.
Ways to evaluate efficacy ("endpoints")
1. Did vaccinated people get sick? (symptoms)
2. Did vaccinated people get severely sick? (hospitalized)
3. Did vaccinated people make large numbers of antibodies?
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Ways to evaluate efficacy ("endpoints")
1. Did vaccinated people get sick? (symptoms)
2. Did vaccinated people get severely sick? (hospitalized)
3. Did vaccinated people make large numbers of antibodies?
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Numbers I am seeing quoted about AstraZeneca efficacy are coming from all over the place including most being about whether it produces a robust antibody response.
(Bad marketing/communication is the cause but it doesn't mean this vaccine isn't effective. )
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(Bad marketing/communication is the cause but it doesn't mean this vaccine isn't effective. )
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*Penicillin was discovered by accident, didn't have a marketing team but still killed bacteria.
(AZ will not make any money off their vaccine "during this pandemic" per their commitment and they have very little financial incentive to want all their vaccine given early.)
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(AZ will not make any money off their vaccine "during this pandemic" per their commitment and they have very little financial incentive to want all their vaccine given early.)
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Most numbers you see quoted about the efficacy of the Pfizer vaccine have revolved around whether or not the vaccinated person gets sick or severely sick.
*(this is where the 95% number is coming from)
6/n https://www.nejm.org/doi/full/10.1056/NEJMoa2034577
*(this is where the 95% number is coming from)
6/n https://www.nejm.org/doi/full/10.1056/NEJMoa2034577
So when Pfizer says: Our vaccine is "95% effective," what they are saying is:
95% of people who were vaccinated did not have ANY symptoms of COVID. (positive test plus symptoms)
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95% of people who were vaccinated did not have ANY symptoms of COVID. (positive test plus symptoms)
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Using a similar mark for the AstraZeneca vaccine:
The AZ vaccine was 73% effective at preventing COVID symptoms (plus positive test).
*page 34 of British MHRA below
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https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/949772/UKPAR_COVID_19_Vaccine_AstraZeneca_05.01.2021.pdf
The AZ vaccine was 73% effective at preventing COVID symptoms (plus positive test).
*page 34 of British MHRA below
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https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/949772/UKPAR_COVID_19_Vaccine_AstraZeneca_05.01.2021.pdf
However, IMPORTANTLY,
of those who received the AstraZeneca vaccine, beyond 10 days after receiving the vaccine, not a single person was hospitalized.
By this measure, we would call the AZ vaccine 100 percent effective.
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https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/949772/UKPAR_COVID_19_Vaccine_AstraZeneca_05.01.2021.pdf
of those who received the AstraZeneca vaccine, beyond 10 days after receiving the vaccine, not a single person was hospitalized.
By this measure, we would call the AZ vaccine 100 percent effective.
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https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/949772/UKPAR_COVID_19_Vaccine_AstraZeneca_05.01.2021.pdf
Of note, subsequent analysis of the AstraZeneca shows if doses are given over 12 weeks apart that over 80% of people have a robust level of ANTIBODIES in their blood stream.
This would indicate to scientists that this vaccine is AT LEAST 80% effective. (12 weeks - dosing)
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This would indicate to scientists that this vaccine is AT LEAST 80% effective. (12 weeks - dosing)
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"AT LEAST" because those 20% in the AstraZeneca who don't show robust antibodies likely still have a primed immune system that will keep them from getting very sick.
(COVID for these people would likely be more like a cold)
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(COVID for these people would likely be more like a cold)
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All of these numbers are different ways of analyzing efficacy. None of them are wrong. They are like different ways of describing a complex picture. But, the data is clear:
The Moderna/Pfizer AND AstraZeneca are all highly effective, very safe vaccines.
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The Moderna/Pfizer AND AstraZeneca are all highly effective, very safe vaccines.
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If we did not have a pandemic, the approval of the AstraZeneca vaccine should be delayed to determine the effectiveness in people over 65 and the ideal dosing separation.
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But WE ARE IN A PANDEMIC and there are consequences to delaying approval of a vaccine that is clearly effective and safe.
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Many of the "distribution" problems we are facing with the Pfizer/Moderna vaccines are so challenging because these vaccines are difficult to distribute. They require $10k freezers to store, specialty handling to ship.
Ask your PCP or even CVS if they have a $10k freezer
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Ask your PCP or even CVS if they have a $10k freezer
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In contrast, the AstraZeneca vaccine is $3 per dose and can be stored without specialty freezers.
If you want vaccines on every street corner and stadiums then this vaccine approval is CRITICAL.
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If you want vaccines on every street corner and stadiums then this vaccine approval is CRITICAL.
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If they FDA feels compelled to get more information, then they should approve the AstraZeneca for people under 65 for now and prioritize does of Pfizer/Moderna for those over 65 until we have more data. (measured response)
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Of note, I think the data is suggestive that the AstraZeneca vaccine may take slightly longer to develop immunity than the Pfizer. If this is the case, then it seems like we should be giving Pfizer/Moderna to over 65 folks anyway and AZ to under 65.
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***Please note there is an error in tweet number 7 in the way I described the data: It should be read that with the Pfizer vaccine there is a 95% reduction in expected cases which the number of expected cases is derived from the control group.
***Please note there is an error in tweet number 7 in the way I described the data: It should be read that with the Pfizer vaccine there is a 95% reduction in expected cases which the number of expected cases is derived from the control group.
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The central point of this thread which is not changed by the error described in tweet 19 is that the Pfizer, Moderna and AstraZeneca vaccines all demonstrate robust safety and effectiveness.
The central point of this thread which is not changed by the error described in tweet 19 is that the Pfizer, Moderna and AstraZeneca vaccines all demonstrate robust safety and effectiveness.
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This expert takes a similar but different view on some of these issues. Again, I am a practicing clinician self interpreting data. My perspective is that of an American who does not agree with prolonged process of AZ review costing lives by @US_FDA https://threader.app/thread/1349135134776119296
This expert takes a similar but different view on some of these issues. Again, I am a practicing clinician self interpreting data. My perspective is that of an American who does not agree with prolonged process of AZ review costing lives by @US_FDA https://threader.app/thread/1349135134776119296
