2/ Though B.1.1.7 was especially prominent in Kent, the 2nd sequence ever sequenced was found in London, a day after the 1st. Due to superspreading it isn't possible to pinpoint for sure whether it originated in Kent or London. (If London, there's no argument for the continent).
3/ And suppose we did believe the new variant was introduced from abroad. Would we expect it to be introduced by sea or air? Far more arrivals to the UK in August/September occurred by air compared to sea.
4/ Genetic evidence. Suppose this highly transmissible variant had arisen in some other country, and made its way through France to the UK. It would also have left lots of descendants in Europe. We can look at a genetic tree of sequences and see that that is not the case.
5/ The grey/orange sequences here are UK sequences and the others are from an array of other countries. Specifically I've highlighted a lineage in Denmark which represents spread from a single introduction to Denmark, ultimately from the UK.
6/ Given there is evidence of spread from a single point in the UK, if the UK was not the source of the outbreak we'd expect all these UK grey sequences to group together, like these Danish sequences do.
7/ We'd expect to see at least some European "outgroups", looking like more distant relations on the family tree. But we don't.
9/ One doesn't even necessarily need to invoke these phylogenetic arguments. We've seen how quickly this strain has taken over in the UK. We know it has not yet taken over in France. If it had existed in France before the UK, it would be the dominant strain there already.
• • •
Missing some Tweet in this thread? You can try to
force a refresh
Completely understand why people are peeved, esp. given GISAID policy. But eventually we should build a system with best of both worlds
- labs rewarded for making data publicly available quickly
- this data freely analysed by anyone, and those analyses communicated (=published)
1/ The MHRA has approved a longer gap between doses for both the AstraZeneca vaccine and the Pfizer vaccine. The latter has concerned some people. Specifically many are citing a figure of 52% for protection after the first dose.
Here is why this 52% figure isn't useful [1/n]
2/ The 52% value is a real figure, which comes from the Pfizer trial, for the period between the first and second doses. Here is what that period of time looked like (fda.gov/media/144325/d…):
In red are people who received placebo and in blue are those who received the vaccine
3/ We can see that until day 3 we have near identical results in both groups. This is *expected* - no vaccine has an effect until days later when the immune system has had time to develop a response against it.
And we can then compare this to the rate of growth in case figures week-on-week. (N.B. the already published analysis from PHE and others does this in much better more sophisticated ways, it's just interesting to explore)