Authors Sandy Douglas
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This issue is, appropriately, contentious. As a vaccinologist - & citizen & relative of people in at-risk groups - I fully support the UK decision to increase dose intervals of both our Ox/AZ product and the Pfizer product. I'd happily receive either with a >8w gap. Here's why 🧵
For the Ox/AZ vaccine, it's fairly simple. The trial demonstrated efficacy at a range of dose intervals. Antibody responses after the boost were significantly stronger with longer intervals - see table
(so in response to @drmarkporter's point, higher immune responses with a longer interval is proven & now public. I haven't seen a similar analysis for efficacy against disease but the data exists and I suspect the regulators & JCVI committee have)
For Pfizer, there isn't direct evidence of efficacy with a >3wk interval. But as widely publicised, efficacy in the period from 14 days after first dose to 21 days is high.
Can we extrapolate from this to a longer interval? It's a judgment call. On one hand is evidence-based medicine's scepticism of anything not directly proven 'beyond reasonable doubt' in an RCT; on the other is a 'balance of probabilities' approach based upon the biology.
Short cut to JCVI rationale behind extending interval between doses of #covidvaccine (thanks @mgtmccartney)
— Dr Mark Porter (@drmarkporter) January 1, 2021
Note efficacy is "calculated" rather than proven at this stage.https://t.co/EbZWcJYkFt
For the Ox/AZ vaccine, it's fairly simple. The trial demonstrated efficacy at a range of dose intervals. Antibody responses after the boost were significantly stronger with longer intervals - see table
(so in response to @drmarkporter's point, higher immune responses with a longer interval is proven & now public. I haven't seen a similar analysis for efficacy against disease but the data exists and I suspect the regulators & JCVI committee have)
For Pfizer, there isn't direct evidence of efficacy with a >3wk interval. But as widely publicised, efficacy in the period from 14 days after first dose to 21 days is high.
Can we extrapolate from this to a longer interval? It's a judgment call. On one hand is evidence-based medicine's scepticism of anything not directly proven 'beyond reasonable doubt' in an RCT; on the other is a 'balance of probabilities' approach based upon the biology.
Amazing news. Our team @JennerInstitute are so pleased to see this!
A few quick responses to some pointing out it could be even better (more/cheaper/single-dose) 1/
The Ox/AZ/SerumInst deal is incredibly radical- Ox opted out of £££ to make a brand new product available around the world not-for-profit. Please judge imperfections by comparison to Pfizer/Moderna, not vs an imaginary ideal or a company which hasn’t yet delivered any doses.
Quibble #1: ‘It needs 2 doses’. Ox/AZ haven’t done as good a PR job on this as J&J, but the vaccines are similar. Published Ox data shows substantial single dose efficacy if you read tables carefully. Further analysis will be done soon. 2/
And I think all vaccines incl J&J will need boost for optimal long-term effect. 3/
Quibble #2: ‘But Serum Inst are charging more to SA than AZ are charging others’. Firstly, the product remains cheaper, I think, than anything else in market, or many older vaccines which haven’t had the recent R&D costs. 4/
A few quick responses to some pointing out it could be even better (more/cheaper/single-dose) 1/
The first shipment of 1 million doses of the #OxfordAstraZeneca vaccine from the @SerumInstIndia is on the way to @ortambo_int
— South African Government (@GovernmentZA) January 31, 2021
The shipment left the Chhatrapati Shivaji Maharaj International Airport in Mumbai today and will arrive in South Africa on 1 February 2021.#COVID19 pic.twitter.com/lTw1EtGi0d
The Ox/AZ/SerumInst deal is incredibly radical- Ox opted out of £££ to make a brand new product available around the world not-for-profit. Please judge imperfections by comparison to Pfizer/Moderna, not vs an imaginary ideal or a company which hasn’t yet delivered any doses.
Quibble #1: ‘It needs 2 doses’. Ox/AZ haven’t done as good a PR job on this as J&J, but the vaccines are similar. Published Ox data shows substantial single dose efficacy if you read tables carefully. Further analysis will be done soon. 2/
And I think all vaccines incl J&J will need boost for optimal long-term effect. 3/
Quibble #2: ‘But Serum Inst are charging more to SA than AZ are charging others’. Firstly, the product remains cheaper, I think, than anything else in market, or many older vaccines which haven’t had the recent R&D costs. 4/