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Thu Feb 18, 2021, 06:18 PM

Change urged to single vaccine dosing for Pfizer. Moderna not sure about South African variant
















eta: sorry, had to edit subject line, Pfizer did not say this. First tweet headline was wrong.

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Reply Change urged to single vaccine dosing for Pfizer. Moderna not sure about South African variant (Original post)
steve2470 Feb 18 OP
Yonnie3 Feb 18 #1
Pobeka Feb 18 #2
Blue_true Feb 18 #3
Pobeka Feb 18 #4
Blue_true Feb 18 #5

Response to steve2470 (Original post)

Thu Feb 18, 2021, 06:27 PM

1. Thanks for updating your title n/t

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Response to steve2470 (Original post)

Thu Feb 18, 2021, 07:48 PM

2. This is potentially awesome, but probably nothing at all.

I don't claim to understand the Pfizer protocols, but

a) If everyone got the two doses in the trials, and the dose spacing was 3-4 weeks, then what the article is claiming is that in the final 1 or 2 week period after the first dose, only 5% of the vaccinated individuals got symptoms. It would not give any way to assess efficacy beyond that 1 or 2 week period, because individuals got a second dose after a total period of 3-4 weeks, and there is no long term data to support an efficacy estimate for a single dose.

b) If some of the individuals in the trials only got a single dose, then this could be valid.

My guess if there was a second test group that only got one dose, Pfizer would already know the answer about the long term efficacy of a single dose and we'd have started with the one dose regimen.

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Response to Pobeka (Reply #2)

Thu Feb 18, 2021, 07:56 PM

3. I agree with your last paragraph.

Pfizer must have developed the one dose data from recently vaccinated people. And like you, I am trying to figure out what “after 2 weeks mean”, does that mean a person is good against SARS-COV-2 for as long as the people that get two doses, or does it mean that once the vaccine kicks in 2 weeks, a person is good for an as yet undetermined time?

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Response to Blue_true (Reply #3)

Thu Feb 18, 2021, 08:27 PM

4. I checked -- the Pfizer phase III trial was only 2 doses, or a placebo

There is no long term 1 dose study.

Answers the question.

https://pfe-pfizercom-d8-prod.s3.amazonaws.com/2020-11/C4591001_Clinical_Protocol_Nov2020.pdf

Caveat -- I haven't read the whole thing, but it appears that the phase I trial may have attempted to get some estimates from 1 dose (no -- see edit below), in subsequent phase 2/3 trials they only used 2 doses, which I assume means they learned 2 doses were required to get sufficient immunity.

on edit: -- even phase 1 protocol was 2 doses, according to the pdf referenced.

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Response to Pobeka (Reply #4)

Thu Feb 18, 2021, 08:30 PM

5. I have to agree with your assessment. Why recommend two doses if

they had compelling data showing that one dose did the job.

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