The AZ/oxford vac shows high immunogenicity and efficacy when delayed to 12 weeks for 2nd dose. Ab titres highest for 12 weeks ๐
BUT the delay for Pfizer vac though potential large societal benefits is definitely a risk...
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BUT the delay for Pfizer vac though potential large societal benefits is definitely a risk...
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1. Pfizer efficacy was only trialled at 21 days for 2nd dose. (cf AZ/Ox 4-26 weeks)
2. This can be estimated at ~80-90% for 10-22 days after 1st dose
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2. This can be estimated at ~80-90% for 10-22 days after 1st dose
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https://twitter.com/theosanderson/status/1344347389642088451
But Ab tires don't increase until 2nd dose for Pfizer, especially in the older age cohort who are the priority vaccine targets. How much protection are we giving them?๐
The 86% is a pooled estimate of all ages with younger population dominating.
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The 86% is a pooled estimate of all ages with younger population dominating.
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Duration of protection: there is no published data in any paper or from MHRA/JVCI to 12 weeks after 1st dose of Pfizer. The efficacy could wane, we don't know how much or how quick.
Or if delayed 2nd dose would bring us back to 95% efficacy like the 21 day interval regime.
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Or if delayed 2nd dose would bring us back to 95% efficacy like the 21 day interval regime.
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Vaccine Resistance:
In the UK we have maximized viral population size and diversity with high prevalence and growth rate. Partial or waning immunity will titrate a selection pressure for vac induced Ab/T-cell recognition escape. This would be V. V. bad!
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In the UK we have maximized viral population size and diversity with high prevalence and growth rate. Partial or waning immunity will titrate a selection pressure for vac induced Ab/T-cell recognition escape. This would be V. V. bad!
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The patients upto 30 Dec were consented for Pfizer vac explicitly on the benefits/risks/data of a 21 day interval.
That consent is invalid, those patients are now effectively in a trial. This is a major issue of medical ethics & trust. Maybe urgency of the pandemic overrides
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That consent is invalid, those patients are now effectively in a trial. This is a major issue of medical ethics & trust. Maybe urgency of the pandemic overrides
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Complexity of cancelling and reorganising 3/4 million 2nd doses appointments across GPs and Hosp hubs is astounding and a major distraction of man power. Especially difficult for 80+ ages who may need carers and transport.
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Those are the risks/costs of extending Pfizer regime. The benefit would be 1-2 million partially vaccinated/immune people over 9 weeks. As AZ/Ox ramps up to 2 mil/week. We'd be upto a week ahead compared to standard regime for Pfizer while the pandemic is raging and killing. Hard
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