Informative paper - B117 (SGTF) viral load and transmission dynamics for test strategies

They linked 1m INDEX cases in England to PCR+ contacts across settings by age (not what PHE did)

B117https://abs.twimg.com/emoji/v2/... draggable="false" alt="⬆️" title="Pfeil nach oben" aria-label="Emoji: Pfeil nach oben">transmissibility but relatively more in young...

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https://www.medrxiv.org/content/10.1101/2021.03.31.21254687v1.full.pdf">https://www.medrxiv.org/content/1...

Absolute transmission probability (proportion of contacts PCR+) remained much higher for older ages as seen above: ADULT transmission still dominates.

However, B117 increased relative transmissibility more in younger ages (esp kids/10yo) across contact settings https://abs.twimg.com/emoji/v2/... draggable="false" alt="👇" title="Rückhand Zeigefinger nach unten" aria-label="Emoji: Rückhand Zeigefinger nach unten">

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This adds to a lovely modelling paper by @SarahDRasmussen (+ prev Imperial) demonstrating the shifting distribution of B117 cases towards these younger 0-19 ages.
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"likely...larger relative increase in infectiousness"

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https://twitter.com/SarahDRasmussen/status/1374118553650085892">https://twitter.com/SarahDRas...

B117 has mutations affecting virus entry- https://abs.twimg.com/emoji/v2/... draggable="false" alt="⬆️" title="Pfeil nach oben" aria-label="Emoji: Pfeil nach oben">affinity for ACE2 receptor (N501Y) and https://abs.twimg.com/emoji/v2/... draggable="false" alt="⬆️" title="Pfeil nach oben" aria-label="Emoji: Pfeil nach oben">replicative efficiency (del69/70).

Kids were/are less susceptible and transmit less.
They express less ACE2 and have lower viral load when infected.

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Relative changes to efficiency of viral entry and replication should logically have more impact in these marginal scenarios.

However, in the grand scheme of things data demonstrates the risk to children and from children driving transmission remains extremely low.

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B117 may slightlyhttps://abs.twimg.com/emoji/v2/... draggable="false" alt="⬆️" title="Pfeil nach oben" aria-label="Emoji: Pfeil nach oben">relative young transmission but open English schools shows impact v small/manageable. The social, developmental and health gains are immense.

For balanced evidence from an expert paeds infectious disease doc highly recommend @apsmunro https://dontforgetthebubbles.com/evidence-summary-paediatric-covid-19-literature/">https://dontforgetthebubbles.com/evidence-...