THREAD There’s much debate around the UK's recommended use of the AZ vaccine with a two-dose schedule and flexible timing of second dose. Some thoughts on the AZ recommendation (not Pfizer) based on available data with refs to some excellent threads. 1/https://twitter.com/HelenBranswell/status/1344306446910058496?s=20 …
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There’s nothing magic about the (short) 28d interval between doses, which was presumably chosen to ensure rapid onset of protection in Ph3. Vaccine efficacy won't disappear overnight with a delayed 2nd dose - it will wane over time, if at all. Ph3 data supports that concept. 9/
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Yes there are risks of waning immunity, non-compliance with the second dose, confusion among the public, etc. Many are implementation considerations that can be addressed with planning and strong communication. 10/
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It will be critically important to collect efficacy data around this “flexible second dose” schedule, esp in older adults & against severe disease, to inform licensure and recommendations in countries around the world that are counting on the introduction of this vaccine. 11/
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Yes the AZ/Oxford studies had a number of issues, but we must remember that this highly-complex development program was executed in less than a year. And that Pfizer & Moderna's Ph3 execution & vaccine efficacy created very high expectations for all subsequent programs. 12/
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The bottom line is that every country needs to make difficult policy decisions with the data they have, not what they'd like to have. There's no perfect answer here, but now that a decision has been taken, the UK can focus on maximizing the benefit and mitigating any risks. 13/
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I didn't address question of adjusting the mRNA vaccine schedule, mainly due to lack of data, and was glad to see
@VirusesImmunity posted her expert thoughts on the topic. 14/https://twitter.com/VirusesImmunity/status/1345086669607890945?s=20 …Show this thread
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