1/5 I had hoped @PHE_uk would look at the evidence on smoking, vaping and COVID-19 in the round, take expert advice, and update advice on a rolling basis.

But what they have done is terrible:
https://www.gov.uk/government/news/smokers-at-greater-risk-of-severe-respiratory-disease-from-covid-19

It looks like crass PR rather than sound science.

2/ It draws on a single study from China of 78 subjects who were *already* very sick with COVID-19-induced pneumonia.
https://journals.lww.com/cmj/Abstract/publishahead/Analysis_of_factors_associated_with_disease.99363.aspx

Of the 78, 11 deteriorated. Of the 78, 5 were smokers, 3 deteriorated and 2 improved. This is the basis for the 14x headline risk claim.

3/ But this overlooks a very important detail. Of the 78 included in the study, there were only 5 smokers (6.4%). Yet smoking prevalence in China is about 27% (52% men, 3% women). So smokers are dramatically underrepresented in those already very sick with pneumonia. Why?

4/ It gets worse. Of the 11 who deteriorated, 7 (67%) were men. But it is clear men generally are more likely to develop severe symptoms once they have the disease (maybe due to immune system differences).
https://globalhealth5050.org/covid19/ 

So the smoking effect could be a 'male' effect.

5/5 PHE is giving advice on the basis of a single study, which is bad enough. But it ignores the striking underrepresentation of smokers in the sample and misrepresents the findings of the study as general advice to smokers.

Where's @SwitchFinder? We need sound science from PHE.